Molecules

26 pages, 2426 KiB

Open AccessEditor’s ChoiceReview

Investigating Biomolecules in Deep Eutectic Solvents with Molecular Dynamics Simulations: Current State, Challenges and Future Perspectives

by Jan Philipp Bittner, Irina Smirnova and Sven Jakobtorweihen

Molecules 2024, 29(3), 703; https://doi.org/10.3390/molecules29030703 - 2 Feb 2024

Cited by 20 | Viewed by 3517

Abstract

Deep eutectic solvents (DESs) have recently gained increased attention for their potential in biotechnological applications. DESs are binary mixtures often consisting of a hydrogen bond acceptor and a hydrogen bond donor, which allows for tailoring their properties for particular applications. If produced from [...] Read more.

Deep eutectic solvents (DESs) have recently gained increased attention for their potential in biotechnological applications. DESs are binary mixtures often consisting of a hydrogen bond acceptor and a hydrogen bond donor, which allows for tailoring their properties for particular applications. If produced from sustainable resources, they can provide a greener alternative to many traditional organic solvents for usage in various applications (e.g., as reaction environment, crystallization agent, or storage medium). To navigate this large design space, it is crucial to comprehend the behavior of biomolecules (e.g., enzymes, proteins, cofactors, and DNA) in DESs and the impact of their individual components. Molecular dynamics (MD) simulations offer a powerful tool for understanding thermodynamic and transport processes at the atomic level and offer insights into their fundamental phenomena, which may not be accessible through experiments. While the experimental investigation of DESs for various biotechnological applications is well progressed, a thorough investigation of biomolecules in DESs via MD simulations has only gained popularity in recent years. Within this work, we aim to provide an overview of the current state of modeling biomolecules with MD simulations in DESs and discuss future directions with a focus for optimizing the molecular simulations and increasing our fundamental knowledge. Full article

(This article belongs to the Special Issue New Advances in Deep Eutectic Solvents)

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16 pages, 2964 KiB

Open AccessEditor’s ChoiceArticle

Physico-Chemical Investigation and Antimicrobial Efficacy of Ozonated Oils: The Case Study of Commercial Ozonated Olive and Sunflower Seed Refined Oils

by Silvia Puxeddu, Alessandra Scano, Mariano Andrea Scorciapino, Ilenia Delogu, Sarah Vascellari, Guido Ennas, Aldo Manzin and Fabrizio Angius

Molecules 2024, 29(3), 679; https://doi.org/10.3390/molecules29030679 - 1 Feb 2024

Cited by 13 | Viewed by 3714

Abstract

Drug resistance represents one of the great plagues of our time worldwide. This largely limits the treatment of common infections and requires the development of new antibiotics or other alternative approaches. Noteworthy, the indiscriminate use of antibiotics is mostly responsible for the selection [...] Read more.

Drug resistance represents one of the great plagues of our time worldwide. This largely limits the treatment of common infections and requires the development of new antibiotics or other alternative approaches. Noteworthy, the indiscriminate use of antibiotics is mostly responsible for the selection of mutations that confer drug resistance to microbes. In this regard, recently, ozone has been raising interest for its unique biological properties when dissolved in natural oils. Ozonated oils have been reported to act in a non-specific way on microorganisms hindering the acquisition of advantageous mutations that result in resistance. Here, we focused on the antimicrobial effect of two commercial olive (OOO) and sunflower seeds (OSO) oils. Nuclear magnetic resonance spectroscopy and thermal analysis showed the change in the chemical composition of the oils after ozonation treatment. Different ozonated oil concentrations were then used to evaluate their antimicrobial profile against Candida albicans, Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli by agar diffusion and broth dilution methods. Cytotoxicity was also evaluated in keratinocytes and epithelial cells. Overall, our results revealed that both OOO and OSO showed a potent microbicidal effect, especially against C. albicans (IC50 = OOO: 0.3 mg/mL and OSO: 0.2 mg/mL) and E. faecalis (IC50 = OOO: 0.4 mg/mL and OSO: 2.8 mg/mL) albeit exerting a certain effect also against S. aureus and E. coli. Moreover, both OOO and OSO do not yield any relevant cytotoxic effect at the active concentrations in both cell lines. This indicates that the ozonated oils studied are not toxic for mammalian cells despite exerting a potent antimicrobial effect on specific microorganisms. Therefore, OOO and OSO may be considered to integrate standard therapies in the treatment of common infections, likely overcoming drug resistance issues. Full article

(This article belongs to the Special Issue Advances of Oleochemistry and Its Application)

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31 pages, 7418 KiB

Open AccessEditor’s ChoiceReview

Rare Earths—The Answer to Everything

by Thomas Behrsing, Victoria L. Blair, Florian Jaroschik, Glen B. Deacon and Peter C. Junk

Molecules 2024, 29(3), 688; https://doi.org/10.3390/molecules29030688 - 1 Feb 2024

Cited by 15 | Viewed by 13429

Abstract

Rare earths, scandium, yttrium, and the fifteen lanthanoids from lanthanum to lutetium, are classified as critical metals because of their ubiquity in daily life. They are present in magnets in cars, especially electric cars; green electricity generating systems and computers; in steel manufacturing; [...] Read more.

Rare earths, scandium, yttrium, and the fifteen lanthanoids from lanthanum to lutetium, are classified as critical metals because of their ubiquity in daily life. They are present in magnets in cars, especially electric cars; green electricity generating systems and computers; in steel manufacturing; in glass and light emission materials especially for safety lighting and lasers; in exhaust emission catalysts and supports; catalysts in artificial rubber production; in agriculture and animal husbandry; in health and especially cancer diagnosis and treatment; and in a variety of materials and electronic products essential to modern living. They have the potential to replace toxic chromates for corrosion inhibition, in magnetic refrigeration, a variety of new materials, and their role in agriculture may expand. This review examines their role in sustainability, the environment, recycling, corrosion inhibition, crop production, animal feedstocks, catalysis, health, and materials, as well as considering future uses. Full article

(This article belongs to the Special Issue Exclusive Review Papers in ‘Inorganic Chemistry’—Are We Relevant?)

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39 pages, 26999 KiB

Open AccessEditor’s ChoiceReview

Porphyrin-Based Nanomaterials for the Photocatalytic Remediation of Wastewater: Recent Advances and Perspectives

by Nirmal Kumar Shee and Hee-Joon Kim

Molecules 2024, 29(3), 611; https://doi.org/10.3390/molecules29030611 - 26 Jan 2024

Cited by 16 | Viewed by 2596

Abstract

Self-organized, well-defined porphyrin-based nanostructures with controllable sizes and morphologies are in high demand for the photodegradation of hazardous contaminants under sunlight. From this perspective, this review summarizes the development progress in the fabrication of porphyrin-based nanostructures by changing their synthetic strategies and designs. [...] Read more.

Self-organized, well-defined porphyrin-based nanostructures with controllable sizes and morphologies are in high demand for the photodegradation of hazardous contaminants under sunlight. From this perspective, this review summarizes the development progress in the fabrication of porphyrin-based nanostructures by changing their synthetic strategies and designs. Porphyrin-based nanostructures can be fabricated using several methods, including ionic self-assembly, metal–ligand coordination, reprecipitation, and surfactant-assisted methods. The synthetic utility of porphyrins permits the organization of porphyrin building blocks into nanostructures, which can remarkably improve their light-harvesting properties and photostability. The tunable functionalization and distinctive structures of porphyrin nanomaterials trigger the junction of the charge-transfer mechanism and facilitate the photodegradation of pollutant dyes. Finally, porphyrin nanomaterials or porphyrin/metal nanohybrids are explored to amplify their photocatalytic efficiency. Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environmental Technologies and Water Purification)

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23 pages, 6246 KiB

Open AccessEditor’s ChoiceArticle

(1E,3E)-1,4-Dinitro-1,3-butadiene—Synthesis, Spectral Characteristics and Computational Study Based on MEDT, ADME and PASS Simulation

by Mikołaj Sadowski, Beata Synkiewicz-Musialska and Karolina Kula

Molecules 2024, 29(2), 542; https://doi.org/10.3390/molecules29020542 - 22 Jan 2024

Cited by 16 | Viewed by 2327

Abstract

The chemistry of conjugated nitrodienes is becoming increasingly popular. These molecules are successfully applied in cycloaddition to synthesize six-membered rings in Diels-Alder reactions. Nitrodienes can be also applied to obtain bis-compounds in [3+2] cycloaddition. Moreover, the presence of a nitro group in the [...] Read more.

The chemistry of conjugated nitrodienes is becoming increasingly popular. These molecules are successfully applied in cycloaddition to synthesize six-membered rings in Diels-Alder reactions. Nitrodienes can be also applied to obtain bis-compounds in [3+2] cycloaddition. Moreover, the presence of a nitro group in the structure provides a possibility of further modification of the products. The simplest symmetrical representative of conjugated nitrodienes is (1E,3E)-1,4-dinitro-1,3-butadiene. Although the first mentions of the compound date back to the early 1950s, the compound has not yet been examined thoroughly enough. Therefore, in this article, a comprehensive study of (1E,3E)-1,4-dinitro-1,3-butadiene has been described. For this purpose, an experimental study including the synthesis process as well as an evaluation of the spectral characteristics has been conducted. So as to better understand the properties of this compound, a computational study of reactivity indices based on MEDT and also an assessment of pharmacokinetics and biological activity according to ADME and PASS methodologies have been made. On this basis, some future application trends of (1E,3E)-1,4-dinitro-1,3-butadiene have been proposed. Full article

(This article belongs to the Special Issue Synthesis, Functionalization and Applications of Nitrogen-Containing Compounds)

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26 pages, 6144 KiB

Open AccessEditor’s ChoiceReview

Porphyrin-Based Metal-Organic Framework Materials: Design, Construction, and Application in the Field of Photocatalysis

by Chuanyin Tang, Xiaoyu Li, Yingxu Hu, Xin Du, Shuo Wang, Bo Chen and Shengjie Wang

Molecules 2024, 29(2), 467; https://doi.org/10.3390/molecules29020467 - 17 Jan 2024

Cited by 30 | Viewed by 7914

Abstract

Metal-organic frameworks (MOFs) are a novel category of porous crystalline materials with an exceptionally high surface area and adjustable pore structure. They possess a designable composition and can be easily functionalized with different units. Porphyrins with conjugated tetrapyrrole macrocyclic structures can absorb light [...] Read more.

Metal-organic frameworks (MOFs) are a novel category of porous crystalline materials with an exceptionally high surface area and adjustable pore structure. They possess a designable composition and can be easily functionalized with different units. Porphyrins with conjugated tetrapyrrole macrocyclic structures can absorb light from ultraviolet to visible light regions, and their structures and properties can be facilely regulated by altering their peripheral groups or central metal ions. Porphyrin-based MOFs constructed from porphyrin ligands and metal nodes combine the unique features of porphyrins and MOFs as well as overcoming their respective limitations. This paper reviewed the design and construction, light absorption and charge transfer pathways, and strategy for improving the photocatalytic performance of porphyrin-based MOFs, and highlighted the recent progress in the field of CO₂ reduction, hydrogen evolution, organic synthesis, organic pollutant removal, and nitrogen fixation. The intrinsic relationships between the structure and the property of porphyrin-based MOFs received special attention, especially the relationships between the arrangements of porphyrin ligands and metal nods and the charge transfer mechanism. We attempted to provide more valuable information for the design and construction of advanced photocatalysts in the future. Finally, the challenges and future perspectives of the porphyrin-based MOFs are also discussed. Full article

(This article belongs to the Special Issue Metal-Organic Framework-Based Composites: Synthesis and Applications)

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16 pages, 3106 KiB

Open AccessEditor’s ChoiceArticle

Chemical Composition, and Antioxidant and Antimicrobial Activity of Oregano Essential Oil

by Magdalena Walasek-Janusz, Agnieszka Grzegorczyk, Anna Malm, Renata Nurzyńska-Wierdak and Daniel Zalewski

Molecules 2024, 29(2), 435; https://doi.org/10.3390/molecules29020435 - 16 Jan 2024

Cited by 21 | Viewed by 8554

Abstract

Antimicrobial resistance (AMR) is a global public health problem, and the rapid rise in AMR is attributed to the inappropriate and/or overuse of antibiotics. Therefore, alternative antimicrobial agents, including those of natural origin, are being sought for the development of new drugs. The [...] Read more.

Antimicrobial resistance (AMR) is a global public health problem, and the rapid rise in AMR is attributed to the inappropriate and/or overuse of antibiotics. Therefore, alternative antimicrobial agents, including those of natural origin, are being sought for the development of new drugs. The purpose of our study was to analyze the chemical composition, and antimicrobial and antioxidant activities of four oregano essential oils (OEOs) from Poland, Europe, Turkey and the USA. The antimicrobial activity (AMA) was evaluated using 23 strains, including Gram-positive bacteria, Gram-negative bacteria and Candida species. The antioxidant activity (AA) of essential oils (EOs) was determined by the DPPH method. The main component of the EOs tested was carvacrol (76.64–85.70%). The highest amount of this compound was determined in the Polish OEO. The OEOs we tested showed antimicrobial resistance, which was especially strong against fungi (MIC = 0.06–0.25 mg/mL⁻¹). These products also showed high AA (71.42–80.44%). OEOs high in carvacrol should be the subject of further research as potential antimicrobial and antioxidant agents. Full article

(This article belongs to the Special Issue Research of Phenolic Compounds from Natural Source)

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16 pages, 2498 KiB

Open AccessEditor’s ChoiceArticle

Naphthoquinone Derivatives from Angustimassarina populi CF-097565 Display Anti-Tumour Activity in 3D Cultures of Breast Cancer Cells

by Thomas A. Mackenzie, Fernando Reyes, Marta Martínez, Víctor González-Menéndez, Isabel Sánchez, Olga Genilloud, José R. Tormo and María C. Ramos

Molecules 2024, 29(2), 425; https://doi.org/10.3390/molecules29020425 - 15 Jan 2024

Cited by 6 | Viewed by 2195

Abstract

Cancer is one of the leading causes of death worldwide, with breast cancer being the second cause of cancer-related mortality among women. Natural Products (NPs) are one of the main sources for drug discovery. During a screening campaign focused on the identification of [...] Read more.

Cancer is one of the leading causes of death worldwide, with breast cancer being the second cause of cancer-related mortality among women. Natural Products (NPs) are one of the main sources for drug discovery. During a screening campaign focused on the identification of extracts from Fundación MEDINA’s library inhibiting the proliferation of cancer cell lines, a significant bioactivity was observed in extracts from cultures of the fungus Angustimassarina populi CF-097565. Bioassay-guided fractionation of this extract led to the identification and isolation of herbarin (1), 1-hydroxydehydroherbarin (4) plus other three naphthoquinone derivatives of which 3 and 5 are new natural products and 2 is herein described from a natural source for the first time. Four of these compounds (1, 3, 4 and 5) confirmed a specific cytotoxic effect against the human breast cancer cell line MCF-7. To evaluate the therapeutic potential of the compounds isolated, their efficacy was validated in 3D cultures, a cancer model of higher functionality. Additionally, an in-depth study was carried out to test the effect of the compounds in terms of cell mortality, sphere disaggregation, shrinkage, and morphology. The cell profile of the compounds was also compared to that of known cytotoxic compounds with the aim to distinguish the drug mode of action (MoA). The profiles of 1, 3 and 4 showed more biosimilarity between them, different to 5, and even more different to other known cytotoxic agents, suggesting an alternative MoA responsible for their cytotoxicity in 3D cultures. Full article

(This article belongs to the Special Issue Advances in Natural Products and Their Biological Activities)

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12 pages, 645 KiB

Open AccessEditor’s ChoiceArticle

Wastewater Characterization: Chemical Oxygen Demand or Total Organic Carbon Content Measurement?

by László Wojnárovits, Renáta Homlok, Krisztina Kovács, Anna Tegze and Ezsébet Takács

Molecules 2024, 29(2), 405; https://doi.org/10.3390/molecules29020405 - 14 Jan 2024

Cited by 16 | Viewed by 5000

Abstract

The long time (2 h) required for measurement, expensive chemicals (Ag₂SO₄), and toxic reagents (K₂Cr₂O₇, HgSO₄) limit the application of the standard method for measuring the oxygen equivalent of organic content [...] Read more.

The long time (2 h) required for measurement, expensive chemicals (Ag₂SO₄), and toxic reagents (K₂Cr₂O₇, HgSO₄) limit the application of the standard method for measuring the oxygen equivalent of organic content in wastewater (chemical oxygen demand, COD). In recent years, the COD has increasingly been replaced by the total organic carbon (TOC) parameter. Since the limit values of the pollution levels are usually given in terms of the COD, efforts are being made to find the correlation between these parameters. Several papers have published correlation analyses of COD and TOC for industrial and municipal wastewater, but the relationship has not been discussed for individual chemicals. Here, this relationship was investigated using 70 contaminants (laboratory chemicals, pharmaceuticals, and pesticides). The calculated COD values, in most cases, agreed, within ~10%, with the experimental ones; for tetracyclines and some chloroaromatic molecules, the measured values were 20–50% lower than the calculated values. The COD/TOC ratios were between 2 and 3: for macrolides, they were ~3; for fluoroquinolones and tetracyclines, they were ~2. The molecular structure dependence of the ratio necessitates the establishing of the correlation on an individual basis. In advanced oxidation processes (AOPs), the ratio changes during degradation, limiting the application of TOC instead of COD. Full article

(This article belongs to the Special Issue Removal of Pharmaceuticals from Contaminated Water, Wastewater and Sediments)

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13 pages, 1513 KiB

Open AccessEditor’s ChoiceArticle

The Potential of NIR Spectroscopy and Chemometrics to Discriminate Roast Degrees and Predict Volatiles in Coffee

by Stella Green, Emily Fanning, Joy Sim, Graham T. Eyres, Russell Frew and Biniam Kebede

Molecules 2024, 29(2), 318; https://doi.org/10.3390/molecules29020318 - 9 Jan 2024

Cited by 6 | Viewed by 3212

Abstract

This study aimed to establish a rapid and practical method for monitoring and predicting volatile compounds during coffee roasting using near-infrared (NIR) spectroscopy coupled with chemometrics. Washed Arabica coffee beans from Ethiopia and Congo were roasted to industry-validated light, medium, and dark degrees. [...] Read more.

This study aimed to establish a rapid and practical method for monitoring and predicting volatile compounds during coffee roasting using near-infrared (NIR) spectroscopy coupled with chemometrics. Washed Arabica coffee beans from Ethiopia and Congo were roasted to industry-validated light, medium, and dark degrees. Concurrent analysis of the samples was performed using gas chromatography-mass spectrometry (GC-MS) and NIR spectroscopy, generating datasets for partial least squares (PLS) regression analysis. The results showed that NIR spectroscopy successfully differentiated the differently roasted samples, similar to the discrimination achieved by GC-MS. This finding highlights the potential of NIR spectroscopy as a rapid tool for monitoring and standardizing the degree of coffee roasting in the industry. A PLS regression model was developed using Ethiopian samples to explore the feasibility of NIR spectroscopy to indirectly measure the volatiles that are important in classifying the roast degree. For PLSR, the data underwent autoscaling as a preprocessing step, and the optimal number of latent variables (LVs) was determined through cross-validation, utilizing the root mean squared error (RMSE). The model was further validated using Congo samples and successfully predicted (with R² values > 0.75 and low error) over 20 volatile compounds, including furans, ketones, phenols, and pyridines. Overall, this study demonstrates the potential of NIR spectroscopy as a practical and rapid method to complement current techniques for monitoring and predicting volatile compounds during the coffee roasting process. Full article

(This article belongs to the Special Issue Challenges in Food Flavor and Volatile Compounds Analysis)

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16 pages, 6589 KiB

Open AccessEditor’s ChoiceArticle

The Synergy between Nuclear Magnetic Resonance and Density Functional Theory Calculations

by Poul Erik Hansen

Molecules 2024, 29(2), 336; https://doi.org/10.3390/molecules29020336 - 9 Jan 2024

Cited by 8 | Viewed by 2307

Abstract

This paper deals with the synergy between Nuclear Magnetic Resonance (NMR) spectroscopic investigations and DFT calculations, mainly of NMR parameters. Both the liquid and the solid states are discussed here. This text is a mix of published results supplemented with new findings. This [...] Read more.

This paper deals with the synergy between Nuclear Magnetic Resonance (NMR) spectroscopic investigations and DFT calculations, mainly of NMR parameters. Both the liquid and the solid states are discussed here. This text is a mix of published results supplemented with new findings. This paper deals with examples in which useful results could not have been obtained without combining NMR measurements and DFT calculations. Examples of such cases are tautomeric systems in which NMR data are calculated for the tautomers; hydrogen-bonded systems in which better XH bond lengths can be determined; cage compounds for which assignment cannot be made based on NMR data alone; revison of already published structures; ionic compounds for which reference data are not available; assignment of solid-state spectra and crystal forms; and the creation of libraries for biological molecules. In addition to these literature cases, a revision of a cage structure and substituent effects on pyrroles is also discussed. Full article

(This article belongs to the Special Issue New Insights into Nuclear Magnetic Resonance (NMR) Spectroscopy)

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16 pages, 8009 KiB

Open AccessEditor’s ChoiceArticle

Co-Immobilization of Laccase and Mediator into Fe-Doped ZIF-8 Significantly Enhances the Degradation of Organic Pollutants

by Zixuan Li, Qinghong Shi, Xiaoyan Dong and Yan Sun

Molecules 2024, 29(2), 307; https://doi.org/10.3390/molecules29020307 - 7 Jan 2024

Cited by 10 | Viewed by 2555

Abstract

Co-immobilization of laccase and mediator 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) for wastewater treatment could simultaneously achieve the reusability of laccase and avoid secondary pollution caused by the toxic ABTS. Herein, Fe-induced mineralization was proposed to co-immobilize laccase and ABTS into a metal–organic framework (ZIF-8) within [...] Read more.

Co-immobilization of laccase and mediator 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) for wastewater treatment could simultaneously achieve the reusability of laccase and avoid secondary pollution caused by the toxic ABTS. Herein, Fe-induced mineralization was proposed to co-immobilize laccase and ABTS into a metal–organic framework (ZIF-8) within 30 min. Immobilized laccase (Lac@ZIF-8-Fe) prepared at a 1:1 mass ratio of Fe²⁺ to Zn²⁺ exhibited enhanced catalytic efficiency (2.6 times), thermal stability, acid tolerance, and reusability compared to free laccase. ABTS was then co-immobilized to form Lac+ABTS@ZIF-8-Fe (ABTS = 261.7 mg/g). Lac@ZIF-8-Fe exhibited significantly enhanced bisphenol A (BPA) removal performance over free laccase due to the local substrate enrichment effect and improved enzyme stability. Moreover, the Lac+ABTS@ZIF-8-Fe exhibited higher BPA removal efficiency than the free laccase+ABTS system, implying the presence of a proximity effect in Lac+ABTS@ZIF-8-Fe. In the successive malachite green (MG) removal, the MG degradation efficiency by Lac@ZIF-8-Fe was maintained at 96.6% at the fifth reuse with only an extra addition of 0.09 mM ABTS in each cycle. As for Lac+ABTS@ZIF-8-Fe, 58.5% of MG was degraded at the fifth cycle without an extra addition of ABTS. Taken together, this research has provided a novel strategy for the design of a co-immobilized laccase and ABTS system for the degradation of organic pollutants. Full article

(This article belongs to the Special Issue Catalysts: New Materials for Green Chemistry)

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19 pages, 5588 KiB

Open AccessEditor’s ChoiceArticle

Modeling the Blood-Brain Barrier Permeability of Potential Heterocyclic Drugs via Biomimetic IAM Chromatography Technique Combined with QSAR Methodology

by Małgorzata Janicka, Małgorzata Sztanke and Krzysztof Sztanke

Molecules 2024, 29(2), 287; https://doi.org/10.3390/molecules29020287 - 5 Jan 2024

Cited by 9 | Viewed by 2607

Abstract

Penetration through the blood-brain barrier (BBB) is desirable in the case of potential pharmaceuticals acting on the central nervous system (CNS), but is undesirable in the case of drug candidates acting on the peripheral nervous system because it may cause CNS side effects. [...] Read more.

Penetration through the blood-brain barrier (BBB) is desirable in the case of potential pharmaceuticals acting on the central nervous system (CNS), but is undesirable in the case of drug candidates acting on the peripheral nervous system because it may cause CNS side effects. Therefore, modeling of the permeability across the blood-brain barrier (i.e., the logarithm of the brain to blood concentration ratio, log BB) of potential pharmaceuticals should be performed as early as possible in the preclinical phase of drug development. Biomimetic chromatography with immobilized artificial membrane (IAM) and the quantitative structure-activity relationship (QSAR) methodology were successful in modeling the blood-brain barrier permeability of 126 drug candidates, whose experimentally-derived lipophilicity indices and computationally-derived molecular descriptors (such as molecular weight (MW), number of rotatable bonds (NRB), number of hydrogen bond donors (HBD), number of hydrogen bond acceptors (HBA), topological polar surface area (TPSA), and polarizability (α)) varied by class. The QSARs model established by multiple linear regression showed a positive effect of the lipophilicity (log k_w, IAM) and molecular weight of the compound, and a negative effect of the number of hydrogen bond donors and acceptors, on the log BB values. The model has been cross-validated, and all statistics indicate that it is very good and has high predictive ability. The simplicity of the developed model, and its usefulness in screening studies of novel drug candidates that are able to cross the BBB by passive diffusion, are emphasized. Full article

(This article belongs to the Special Issue Heterocyclic Compounds for Drug Design and Drug Discovery)

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43 pages, 12336 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Chemistry and Antioxidant/Anticancer Biology of Monoterpene and Meroterpenoid Natural Product

by Benedict J. Barras, Taotao Ling and Fatima Rivas

Molecules 2024, 29(1), 279; https://doi.org/10.3390/molecules29010279 - 4 Jan 2024

Cited by 15 | Viewed by 5435

Abstract

Monoterpenes and meroterpenes are two large classes of isoprene-based molecules produced by terrestrial plants and unicellular organisms as diverse secondary metabolites. The global rising incidence of cancer has led to a renewed interest in natural products. These monoterpenes and meroterpenes represent a novel [...] Read more.

Monoterpenes and meroterpenes are two large classes of isoprene-based molecules produced by terrestrial plants and unicellular organisms as diverse secondary metabolites. The global rising incidence of cancer has led to a renewed interest in natural products. These monoterpenes and meroterpenes represent a novel source of molecular scaffolds that can serve as medicinal chemistry platforms for the development of potential preclinical leads. Furthermore, some of these natural products are either abundant, or their synthetic strategies are scalable as it will be indicated here, facilitating their derivatization to expand their scope in drug discovery. This review is a collection of representative updates (from 2016–2023) in biologically active monoterpene and meroterpenoid natural products and focuses on the recent findings of the pharmacological potential of these bioactive compounds as well as the newly developed synthetic strategies employed to access them. Particular emphasis will be placed on the anticancer and antioxidant potential of these compounds in order to raise knowledge for further investigations into the development of potential anti-cancer therapeutics. The mounting experimental evidence from various research groups across the globe regarding the use of these natural products at pre-clinical levels, renders them a fast-track research area worth of attention. Full article

(This article belongs to the Special Issue Natural Bioactive Compounds from Traditional Asian Plants)

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25 pages, 9713 KiB

Open AccessEditor’s ChoiceReview

Supercapatteries as Hybrid Electrochemical Energy Storage Devices: Current Status and Future Prospects

by Subarna Rudra, Hyun Woo Seo, Subrata Sarker and Dong Min Kim

Molecules 2024, 29(1), 243; https://doi.org/10.3390/molecules29010243 - 2 Jan 2024

Cited by 47 | Viewed by 6834

Abstract

Among electrochemical energy storage (EES) technologies, rechargeable batteries (RBs) and supercapacitors (SCs) are the two most desired candidates for powering a range of electrical and electronic devices. The RB operates on Faradaic processes, whereas the underlying mechanisms of SCs vary, as non-Faradaic in [...] Read more.

Among electrochemical energy storage (EES) technologies, rechargeable batteries (RBs) and supercapacitors (SCs) are the two most desired candidates for powering a range of electrical and electronic devices. The RB operates on Faradaic processes, whereas the underlying mechanisms of SCs vary, as non-Faradaic in electrical double-layer capacitors (EDLCs), Faradaic at the surface of the electrodes in pseudo-capacitors (PCs), and a combination of both non-Faradaic and Faradaic in hybrid supercapacitors (HSCs). EDLCs offer high power density but low energy density. HSCs take advantage of the Faradaic process without compromising their capacitive nature. Unlike batteries, supercapacitors provide high power density and numerous charge–discharge cycles; however, their energy density lags that of batteries. Supercapatteries, a generic term that refers to hybrid EES devices that combine the merits of EDLCs and RBs, have emerged, bridging the gap between SCs and RBs. There are numerous articles and reviews on EES, and many of those articles have emphasized various aspects of HSCs and supercapatteries. However, there are no recent reviews that dealt with supercapatteries in general. Here, we review recently published critically selected articles on supercapatteries. The review discusses different EES devices and how supercapatteries are different from others. Also discussed are properties, design strategies, and future perspectives on supercapatteries. Full article

(This article belongs to the Special Issue Synthesis and Characterization of Functional Materials for Electrochemical Energy Storage and Conversion)

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27 pages, 1037 KiB

Open AccessEditor’s ChoiceReview

Lignin Extraction by Using Two-Step Fractionation: A Review

by Medya Hatun Tanis, Ola Wallberg, Mats Galbe and Basel Al-Rudainy

Molecules 2024, 29(1), 98; https://doi.org/10.3390/molecules29010098 - 22 Dec 2023

Cited by 37 | Viewed by 7883

Abstract

Lignocellulosic biomass represents the most abundant renewable carbon source on earth and is already used for energy and biofuel production. The pivotal step in the conversion process involving lignocellulosic biomass is pretreatment, which aims to disrupt the lignocellulose matrix. For effective pretreatment, a [...] Read more.

Lignocellulosic biomass represents the most abundant renewable carbon source on earth and is already used for energy and biofuel production. The pivotal step in the conversion process involving lignocellulosic biomass is pretreatment, which aims to disrupt the lignocellulose matrix. For effective pretreatment, a comprehensive understanding of the intricate structure of lignocellulose and its compositional properties during component disintegration and subsequent conversion is essential. The presence of lignin-carbohydrate complexes and covalent interactions between them within the lignocellulosic matrix confers a distinctively labile nature to hemicellulose. Meanwhile, the recalcitrant characteristics of lignin pose challenges in the fractionation process, particularly during delignification. Delignification is a critical step that directly impacts the purity of lignin and facilitates the breakdown of bonds involving lignin and lignin-carbohydrate complexes surrounding cellulose. This article discusses a two-step fractionation approach for efficient lignin extraction, providing viable paths for lignin-based valorization described in the literature. This approach allows for the creation of individual process streams for each component, tailored to extract their corresponding compounds. Full article

(This article belongs to the Special Issue Lignocellulose Fractionation, Depolymerisation, and Upgrading—from Lignin to Valuable Products)

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35 pages, 1587 KiB

Open AccessEditor’s ChoiceReview

Bioactive Dairy-Fermented Products and Phenolic Compounds: Together or Apart

by Barbara Wróblewska, Aleksandra Kuliga and Kinga Wnorowska

Molecules 2023, 28(24), 8081; https://doi.org/10.3390/molecules28248081 - 14 Dec 2023

Cited by 12 | Viewed by 4462

Abstract

Fermented dairy products (e.g., yogurt, kefir, and buttermilk) are significant in the dairy industry. They are less immunoreactive than the raw materials from which they are derived. The attractiveness of these products is based on their bioactivity and properties that induce immune or [...] Read more.

Fermented dairy products (e.g., yogurt, kefir, and buttermilk) are significant in the dairy industry. They are less immunoreactive than the raw materials from which they are derived. The attractiveness of these products is based on their bioactivity and properties that induce immune or anti-inflammatory processes. In the search for new solutions, plant raw materials with beneficial effects have been combined to multiply their effects or obtain new properties. Polyphenols (e.g., flavonoids, phenolic acids, lignans, and stilbenes) are present in fruit and vegetables, but also in coffee, tea, or wine. They reduce the risk of chronic diseases, such as cancer, diabetes, or inflammation. Hence, it is becoming valuable to combine dairy proteins with polyphenols, of which epigallocatechin-3-gallate (EGCG) and chlorogenic acid (CGA) show a particular predisposition to bind to milk proteins (e.g., α-lactalbumin β-lactoglobulin, αs1-casein, and κ-casein). Reducing the allergenicity of milk proteins by combining them with polyphenols is an essential issue. As potential ‘metabolic prebiotics’, they also contribute to stimulating the growth of beneficial bacteria and inhibiting pathogenic bacteria in the human gastrointestinal tract. In silico methods, mainly docking, assess the new structures of conjugates and the consequences of the interactions that are formed between proteins and polyphenols, as well as to predict their action in the body. Full article

(This article belongs to the Special Issue Unveiling the Applications of Bioactive Compounds in Functional Foods for Optimal Human Health)

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13 pages, 2079 KiB

Open AccessEditor’s ChoiceArticle

Influence of ZSM-5 Crystal Size on Methanol-to-Olefin (MTO) vs. Ethanol-to-Aromatics (ETA) Conversion

by Daniel Dittmann, Elif Kaya, Dennis Strassheim and Michael Dyballa

Molecules 2023, 28(24), 8046; https://doi.org/10.3390/molecules28248046 - 12 Dec 2023

Cited by 7 | Viewed by 2126

Abstract

Crystal size is a key parameter of zeolites applied as catalysts. Herein, ZSM-5 crystals with similar physicochemical and acid properties, few defects, and aluminum exclusively in tetrahedral coordination are synthesized and the influence of the crystal size on the MTO and ETA conversion [...] Read more.

Crystal size is a key parameter of zeolites applied as catalysts. Herein, ZSM-5 crystals with similar physicochemical and acid properties, few defects, and aluminum exclusively in tetrahedral coordination are synthesized and the influence of the crystal size on the MTO and ETA conversion is investigated. Short olefins are the main products of the MTO conversion, whereas larger olefins and aromatics dominate the products after ETA conversion. In the case of both feeds, an increased crystal size decreases the catalyst’s lifetime. The MTO conversion over larger ZSM-5 altered the product distribution, which was not the case for the ETA conversion. The reason is that the instantly available aromatics during ETA conversion lead to fast coking and zeolite crystals only active in the outer layers. Thus, the different reactivity of different-sized ZSM-5 is direct proof of a different conversion mechanism for both alcohols. Full article

(This article belongs to the Special Issue Porous Materials as Catalysts and Sorbents)

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20 pages, 7287 KiB

Open AccessEditor’s ChoiceArticle

The Application of Handheld Near-Infrared Spectroscopy and Raman Spectroscopic Imaging for the Identification and Quality Control of Food Products

by Hui Yan, Marina D. G. Neves, Barry M. Wise, Ingrid A. Moraes, Douglas F. Barbin and Heinz W. Siesler

Molecules 2023, 28(23), 7891; https://doi.org/10.3390/molecules28237891 - 1 Dec 2023

Cited by 14 | Viewed by 3086

Abstract

The following investigations describe the potential of handheld NIR spectroscopy and Raman imaging measurements for the identification and authentication of food products. On the one hand, during the last decade, handheld NIR spectroscopy has made the greatest progress among vibrational spectroscopic methods in [...] Read more.

The following investigations describe the potential of handheld NIR spectroscopy and Raman imaging measurements for the identification and authentication of food products. On the one hand, during the last decade, handheld NIR spectroscopy has made the greatest progress among vibrational spectroscopic methods in terms of miniaturization and price/performance ratio, and on the other hand, the Raman spectroscopic imaging method can achieve the best lateral resolution when examining the heterogeneous composition of samples. The utilization of both methods is further enhanced via the combination with chemometric evaluation methods with respect to the detection, identification, and discrimination of illegal counterfeiting of food products. To demonstrate the solution to practical problems with these two spectroscopic techniques, the results of our recent investigations obtained for various industrial processes and customer-relevant product examples have been discussed in this article. Specifically, the monitoring of food extraction processes (e.g., ethanol extraction of clove and water extraction of wolfberry) and the identification of food quality (e.g., differentiation of cocoa nibs and cocoa beans) via handheld NIR spectroscopy, and the detection and quantification of adulterations in powdered dairy products via Raman imaging were outlined in some detail. Although the present work only demonstrates exemplary product and process examples, the applications provide a balanced overview of materials with different physical properties and manufacturing processes in order to be able to derive modified applications for other products or production processes. Full article

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25 pages, 1498 KiB

Open AccessEditor’s ChoiceReview

Molecular Hydrogen Therapy—A Review on Clinical Studies and Outcomes

by Hennie Marie Johnsen, Marianne Hiorth and Jo Klaveness

Molecules 2023, 28(23), 7785; https://doi.org/10.3390/molecules28237785 - 26 Nov 2023

Cited by 45 | Viewed by 38496

Abstract

With its antioxidant properties, hydrogen gas (H₂) has been evaluated in vitro, in animal studies and in human studies for a broad range of therapeutic indications. A simple search of “hydrogen gas” in various medical databases resulted in more than 2000 [...] Read more.

With its antioxidant properties, hydrogen gas (H₂) has been evaluated in vitro, in animal studies and in human studies for a broad range of therapeutic indications. A simple search of “hydrogen gas” in various medical databases resulted in more than 2000 publications related to hydrogen gas as a potential new drug substance. A parallel search in clinical trial registers also generated many hits, reflecting the diversity in ongoing clinical trials involving hydrogen therapy. This review aims to assess and discuss the current findings about hydrogen therapy in the 81 identified clinical trials and 64 scientific publications on human studies. Positive indications have been found in major disease areas including cardiovascular diseases, cancer, respiratory diseases, central nervous system disorders, infections and many more. The available administration methods, which can pose challenges due to hydrogens’ explosive hazards and low solubility, as well as possible future innovative technologies to mitigate these challenges, have been reviewed. Finally, an elaboration to discuss the findings is included with the aim of addressing the following questions: will hydrogen gas be a new drug substance in future clinical practice? If so, what might be the administration form and the clinical indications? Full article

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13 pages, 2370 KiB

Open AccessEditor’s ChoiceArticle

Analytical Methods Based on the Mass Balance Approach for Purity Evaluation of Tetracycline Hydrochloride

by Sunyoung Lee, Song-Yee Baek, Ha-Jeong Kwon, Ki Hwan Choi and Jeesoo Han

Molecules 2023, 28(22), 7568; https://doi.org/10.3390/molecules28227568 - 13 Nov 2023

Cited by 6 | Viewed by 2446

Abstract

Analytical methods based on the mass balance approach were developed for the purity evaluation of tetracycline hydrochloride, a representative salt compound used in pure veterinary drug analysis. The purity assignment method was used to quantify individual classes of impurities via independent analytical techniques. [...] Read more.

Analytical methods based on the mass balance approach were developed for the purity evaluation of tetracycline hydrochloride, a representative salt compound used in pure veterinary drug analysis. The purity assignment method was used to quantify individual classes of impurities via independent analytical techniques. The mass fraction of the free base or salt form contained in a high-purity organic compound with a hydrochloride salt can be determined. The chloride content by ion chromatography-conductivity detector (IC-CD) and general classes of impurities, including structurally related impurities by liquid chromatography–ultraviolet (LC-UV) detector, water by Karl Fischer (KF) coulometric titration, residual solvents by headspace sampler gas chromatography/mass spectrometry (HS-GC/MS), and non-volatiles by thermogravimetric analyzer (TGA), were considered to calculate the purity of the mass fraction. The chloride content of the salt compound can be considered the main impurity in the mass fraction of the free base in the salt compound. A purity assay using quantitative nuclear magnetic resonance (q-NMR) as a direct determination method was performed to confirm the results of the mass balance method. The assigned purities of the tetracycline free form and its salt form in mass fraction were (898.80 ± 1.60) mg/g and (972.65 ± 1.58) mg/g, respectively, which are traceable to the international system of units (SI). Thus, the procedure for evaluating the purity of the free base and salt forms in the salt compound is newly demonstrated in this study. Full article

(This article belongs to the Special Issue Qualitative and Quantitative Analyses of Food and Drugs)

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33 pages, 7062 KiB

Open AccessEditor’s ChoiceReview

Fluoropolymers as Unique and Irreplaceable Materials: Challenges and Future Trends in These Specific Per or Poly-Fluoroalkyl Substances

by Bruno Améduri

Molecules 2023, 28(22), 7564; https://doi.org/10.3390/molecules28227564 - 13 Nov 2023

Cited by 32 | Viewed by 8022

Abstract

In contrast to some low-molar-mass per- and polyfluoroalkyl substances (PFASs), which are well established to be toxic, persistent, bioaccumulative, and mobile, fluoropolymers (FPs) are water-insoluble, safe, bioinert, and durable. These niche high-performance polymers fulfil the 13 polymer-of-low-concern (PLC) criteria in their recommended conditions [...] Read more.

In contrast to some low-molar-mass per- and polyfluoroalkyl substances (PFASs), which are well established to be toxic, persistent, bioaccumulative, and mobile, fluoropolymers (FPs) are water-insoluble, safe, bioinert, and durable. These niche high-performance polymers fulfil the 13 polymer-of-low-concern (PLC) criteria in their recommended conditions of use. In addition, more recent innovations (e.g., the use of non-fluorinated surfactants in aqueous radical (co)polymerization of fluoroalkenes) from industrial manufacturers of FPs are highlighted. This review also aims to show how these specialty polymers endowed with outstanding properties are essential (even irreplaceable, since hydrocarbon polymer alternatives used in similar conditions fail) for our daily life (electronics, energy, optics, internet of things, transportation, etc.) and constitute a special family separate from other “conventional” C₁–C₁₀ PFASs found everywhere on Earth and its oceans. Furthermore, some information reports on their recycling (e.g., the unzipping depolymerization of polytetrafluoroethylene, PTFE, into TFE), end-of-life FPs, and their risk assessment, circular economy, and regulations. Various studies are devoted to environments involving FPs, though they present a niche volume (with a yearly production of 330,300 t) compared to all plastics (with 460 million t). Complementary to other reviews on PFASs, which lack of such above data, this review presents both fundamental and applied strategies as evidenced by major FP producers. Full article

(This article belongs to the Special Issue Advances in Fluoropolymers)

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17 pages, 3326 KiB

Open AccessEditor’s ChoiceArticle

New Sustainable Solvent Extraction Pathways for Rare Earth Metals via Oximes Molecules

by Maria Atanassova, Rositsa Kukeva and Vanya Kurteva

Molecules 2023, 28(22), 7467; https://doi.org/10.3390/molecules28227467 - 7 Nov 2023

Cited by 10 | Viewed by 2281

Abstract

A study on the synergistic extraction of Eu(III) ions with a series of chelating ligands and determination of the process parameters is presented by employing ionic liquids and typical organic diluents. The investigations of the liquid–liquid extraction, commonly applied in the separation science [...] Read more.

A study on the synergistic extraction of Eu(III) ions with a series of chelating ligands and determination of the process parameters is presented by employing ionic liquids and typical organic diluents. The investigations of the liquid–liquid extraction, commonly applied in the separation science of 4f and 5f-ions acidic chelating compounds, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), 4-benzoyl-3-phenyl-5-isoxazolone (HPBI), and 2-thenoyltrifluoroacetone (HTTA) alone and in combination with two synergistic agents, meso-hexamethylpropyleneamine oxime (S2: HM-PAO) and its bis-imine precursor (S1: pre-HM-PAO), are presented. The interaction between the two extractants (acidic/neutral) in deuterochloroform was studied using ¹H, ¹³C, and ¹H-¹H NOESY experiments. Several conclusions are given highlighting the role of the ionic diluent in complexation processes and selectivity with an employment of the two synergistic agents for various metal s-, p-, d-, and f-cations in the Periodic table, with almost 25 metal ions. The objective was to optimize a system for 4f-ions solvent extraction based on the new oxime molecules with β-diketone/isoxazolone/pyrazolone partnership. As detailed above, slight enhancements of extraction efficiencies were obtained either by using basic synergistic agents such as HM-PAO and/or using pre-HM-PAO. A competitive solvent extraction test of nearly 18 f-ions by various ligands (HTTA, S1, S2, and HPBI) and the two mixtures HTTA−S1 and HTTA−S2 diluted in ILs or organic diluents was also conducted in order to evaluate the switchable diluent impact. Additionally, electron paramagnetic resonance (EPR) spectroscopy was used to study the established chemical species with Cu²⁺ cations in the obtained organic extracts involving the two synergistic molecules. Full article

(This article belongs to the Topic Green Twist in Solvent Extraction and Separation of Metal Species)

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21 pages, 6798 KiB

Open AccessEditor’s ChoiceArticle

Synergistic Remediation of Organic Dye by Titanium Dioxide/Reduced Graphene Oxide Nanocomposite

by Martina Kocijan, Lidija Ćurković, Damjan Vengust, Tina Radošević, Vasyl Shvalya, Gil Gonçalves and Matejka Podlogar

Molecules 2023, 28(21), 7326; https://doi.org/10.3390/molecules28217326 - 29 Oct 2023

Cited by 21 | Viewed by 2321

Abstract

In this work, nanocomposites based on titanium dioxide and reduced graphene oxide (TiO₂@rGO) with different weight percentages of rGO (4, 8, and 16 wt%) were prepared by the hydrothermal/solvothermal synthesis method and thermally treated at 300 °C. The prepared nanocomposites were [...] Read more.

In this work, nanocomposites based on titanium dioxide and reduced graphene oxide (TiO₂@rGO) with different weight percentages of rGO (4, 8, and 16 wt%) were prepared by the hydrothermal/solvothermal synthesis method and thermally treated at 300 °C. The prepared nanocomposites were explored for the removal of methylene blue dye (MB) in the presence of simulated solar illumination as well as natural sunlight. The structural, morphological, chemical, and optical properties of the as-synthesized TiO₂@rGO nanocomposites were characterized. The obtained results of the graphene-based nanocomposite materials indicated the existence of interactions between TiO₂ and rGO, i.e., the Ti–O–C bond, which confirmed the successful integration of both components to form the TiO₂@rGO nanocomposites. The addition of rGO increased the specific surface area, decreased the band gap energy, and increased the photocatalytic degradation efficiency of MB from water compared to TiO₂ nanoparticles. The results of photocatalytic activity indicated that the amount of rGO in the prepared TiO₂@rGO nanocomposites played a significant role in the application of different photocatalytic parameters, including the initial dye concentration, catalyst concentration, water environment, and illumination source. Our studies show that the reinforcement of the nanocomposite with 8 wt% of rGO allowed us to obtain the maximum photocatalytic decomposition performance of MB (10 mg·L⁻¹) with a removal percentage of 99.20 after 2 h. Additionally, the obtained results show that the prepared TiO₂@rGO_8 wt% nanocomposite can be used in three consecutive cycles while maintaining photocatalytic activity over 90%. Full article

(This article belongs to the Special Issue Photocatalytic Materials for Environmental Technologies and Water Purification)

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25 pages, 2348 KiB

Open AccessEditor’s ChoiceReview

Mn-Based MRI Contrast Agents: An Overview

by Céline Henoumont, Marie Devreux and Sophie Laurent

Molecules 2023, 28(21), 7275; https://doi.org/10.3390/molecules28217275 - 26 Oct 2023

Cited by 29 | Viewed by 6338

Abstract

MRI contrast agents are required in the clinic to detect some pathologies, such as cancers. Nevertheless, at the moment, only small extracellular and non-specific gadolinium complexes are available for clinicians. Moreover, safety issues have recently emerged concerning the use of gadolinium complexes; hence, [...] Read more.

MRI contrast agents are required in the clinic to detect some pathologies, such as cancers. Nevertheless, at the moment, only small extracellular and non-specific gadolinium complexes are available for clinicians. Moreover, safety issues have recently emerged concerning the use of gadolinium complexes; hence, alternatives are urgently needed. Manganese-based MRI contrast agents could be one of these alternatives and increasing numbers of studies are available in the literature. This review aims at synthesizing all the research, from small Mn complexes to nanoparticular agents, including theranostic agents, to highlight all the efforts already made by the scientific community to obtain highly efficient agents but also evidence of the weaknesses of the developed systems. Full article

(This article belongs to the Special Issue MRI Contrast Agents: Current Challenges and New Progresses)

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13 pages, 1000 KiB

Open AccessEditor’s ChoiceArticle

Selenium Biofortification Effect on Glucosinolate Content of Brassica oleracea var. italic and Eruca vesicaria

by Azra Đulović, Katarina Usanović, Lea Kukoč Modun and Ivica Blažević

Molecules 2023, 28(20), 7203; https://doi.org/10.3390/molecules28207203 - 21 Oct 2023

Cited by 3 | Viewed by 1792

Abstract

Glucosinolates (GSLs) in different plant parts of broccoli (Brassica oleracea var. italic) and rocket (Eruca vesicaria) were analyzed qualitatively and quantitatively before and after treatment with sodium selenate (2 and 5 mM), by their desulfo-counterparts using the UHPLC-DAD-MS/MS technique. [...] Read more.

Glucosinolates (GSLs) in different plant parts of broccoli (Brassica oleracea var. italic) and rocket (Eruca vesicaria) were analyzed qualitatively and quantitatively before and after treatment with sodium selenate (2 and 5 mM), by their desulfo-counterparts using the UHPLC-DAD-MS/MS technique. Twelve GSLs were detected in broccoli (five aliphatic, one arylaliphatic, and six indolic), where 4-(methylsulfanyl)butyl GSL (glucoerucin) was the main one in the roots (4.88–9.89 µmol/g DW), 4-(methylsulfinyl)butyl GSL (glucoraphanin) in stems (0.44–1.11 µmol/g DW), and 4-hydroxyindol-3-ylmethyl GSL (4-hydroxyglucobrassicin) in leaves (0.51–0.60 µmol/g DW). No GSL containing selenium was detected in the treated broccoli. Ten GSLs were detected in rocket (seven aliphatic and three indolic), where 4-(methylsulfanyl)butyl GSL (glucoerucin) was the main one in the roots (4.50–20.59 µmol/g DW) and 4-methoxyindol-3-ylmethyl GSL (4-methoxyglucobrassicin) in the aerial part (0.57–5.69 µmol/g DW). As a result of induced stress by selenium fertilization, the total GSL content generally increased in both plants. In contrast to broccoli, the roots and the aerial part of the rocket treated with a high concentration of sodium selenate contained 4-(methylseleno)butyl GSL (glucoselenoerucin) (0.36–4.48 µmol/g DW). Although methionine-derived GSLs are the most abundant in both plants, the plants’ ability to tolerate selenate and its regulation by selenoglucosinolate production is species- and growth-stage-dependent. Full article

(This article belongs to the Special Issue Organosulfur and Organoselenium Chemistry)

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29 pages, 1600 KiB

Open AccessEditor’s ChoiceReview

Potential Benefits of Antioxidant Phytochemicals in Type 2 Diabetes

by Arman Arabshomali, Shadi Bazzazzadehgan, Fakhri Mahdi and Zia Shariat-Madar

Molecules 2023, 28(20), 7209; https://doi.org/10.3390/molecules28207209 - 21 Oct 2023

Cited by 29 | Viewed by 4756

Abstract

The clinical relationship between diabetes and inflammation is well established. Evidence clearly indicates that disrupting oxidant-antioxidant equilibrium and elevated lipid peroxidation could be a potential mechanism for chronic kidney disease associated with type 2 diabetes mellitus (T2DM). Under diabetic conditions, hyperglycemia, especially inflammation, [...] Read more.

The clinical relationship between diabetes and inflammation is well established. Evidence clearly indicates that disrupting oxidant-antioxidant equilibrium and elevated lipid peroxidation could be a potential mechanism for chronic kidney disease associated with type 2 diabetes mellitus (T2DM). Under diabetic conditions, hyperglycemia, especially inflammation, and increased reactive oxygen species generation are bidirectionally associated. Inflammation, oxidative stress, and tissue damage are believed to play a role in the development of diabetes. Although the exact mechanism underlying oxidative stress and its impact on diabetes progression remains uncertain, the hyperglycemia-inflammation-oxidative stress interaction clearly plays a significant role in the onset and progression of vascular disease, kidney disease, hepatic injury, and pancreas damage and, therefore, holds promise as a therapeutic target. Evidence strongly indicates that the use of multiple antidiabetic medications fails to achieve the normal range for glycated hemoglobin targets, signifying treatment-resistant diabetes. Antioxidants with polyphenols are considered useful as adjuvant therapy for their potential anti-inflammatory effect and antioxidant activity. We aimed to analyze the current major points reported in preclinical, in vivo, and clinical studies of antioxidants in the prevention or treatment of inflammation in T2DM. Then, we will share our speculative vision for future diabetes clinical trials. Full article

(This article belongs to the Special Issue Bioactive Molecules Targeting Inflammation Processes in Related Diseases)

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12 pages, 1958 KiB

Open AccessEditor’s ChoiceArticle

Lysozyme Inhibitors as Tools for Lysozyme Profiling: Identification and Antibacterial Function of Lysozymes in the Hemolymph of the Blue Mussel

by Lise Vanderkelen, Joris M. Van Herreweghe and Chris W. Michiels

Molecules 2023, 28(20), 7071; https://doi.org/10.3390/molecules28207071 - 13 Oct 2023

Cited by 7 | Viewed by 2654

Abstract

Lysozymes are universal components of the innate immune system of animals that kill bacteria by hydrolyzing their main cell wall polymer, peptidoglycan. Three main families of lysozyme have been identified, designated as chicken (c)-, goose (g)- and invertebrate (i)-type. In response, bacteria have [...] Read more.

Lysozymes are universal components of the innate immune system of animals that kill bacteria by hydrolyzing their main cell wall polymer, peptidoglycan. Three main families of lysozyme have been identified, designated as chicken (c)-, goose (g)- and invertebrate (i)-type. In response, bacteria have evolved specific protein inhibitors against each of the three lysozyme families. In this study, we developed a serial array of three affinity matrices functionalized with a c-, g-, and i-type inhibitors for lysozyme typing, i.e., to detect and differentiate lysozymes in fluids or extracts from animals. The tool was validated on the blue mussel (Mytilus edulis), whose genome carries multiple putative i-, g-, and c-type lysozyme genes. Hemolymph plasma of the animals was found to contain both i- and g-type, but not c-type lysozyme. Furthermore, hemolymph survival of Aeromonas hydrophila and E. coli strains lacking or overproducing the i- type or g-type lysozyme inhibitor, respectively, was analyzed to study the role of the two lysozymes in innate immunity. The results demonstrated an active role for the g-type lysozyme in the innate immunity of the blue mussel, but failed to show a contribution by the i-type lysozyme. Lysozyme profiling using inhibitor-based affinity chromatography will be a useful novel tool for studying animal innate immunity. Full article

(This article belongs to the Special Issue Recent Advances in Lysozyme)

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67 pages, 34211 KiB

Open AccessEditor’s ChoiceReview

Chemistry of Carbon-Substituted Derivatives of Cobalt Bis(dicarbollide)(1⁻) Ion and Recent Progress in Boron Substitution

by Lucia Pazderová, Ece Zeynep Tüzün, Dmytro Bavol, Miroslava Litecká, Lukáš Fojt and Bohumír Grűner

Molecules 2023, 28(19), 6971; https://doi.org/10.3390/molecules28196971 - 7 Oct 2023

Cited by 14 | Viewed by 2749

Abstract

The cobalt bis(dicarbollide)(1⁻) anion (1⁻), [(1,2-C₂B₉H₁₁)₂-3,3′-Co(III)](1⁻), plays an increasingly important role in material science and medicine due to its high chemical stability, 3D shape, aromaticity, diamagnetic character, ability [...] Read more.

The cobalt bis(dicarbollide)(1⁻) anion (1⁻), [(1,2-C₂B₉H₁₁)₂-3,3′-Co(III)](1⁻), plays an increasingly important role in material science and medicine due to its high chemical stability, 3D shape, aromaticity, diamagnetic character, ability to penetrate cells, and low cytotoxicity. A key factor enabling the incorporation of this ion into larger organic molecules, biomolecules, and materials, as well as its capacity for “tuning” interactions with therapeutic targets, is the availability of synthetic routes that enable easy modifications with a wide selection of functional groups. Regarding the modification of the dicarbollide cage, syntheses leading to substitutions on boron atoms are better established. These methods primarily involve ring cleavage of the ether rings in species containing an oxonium oxygen atom connected to the B(8) site. These pathways are accessible with a broad range of nucleophiles. In contrast, the chemistry on carbon vertices has remained less elaborated over the previous decades due to a lack of reliable methods that permit direct and straightforward cage modifications. In this review, we present a survey of methods based on metalation reactions on the acidic C-H vertices, followed by reactions with electrophiles, which have gained importance in only the last decade. These methods now represent the primary trends in the modifications of cage carbon atoms. We discuss the scope of currently available approaches, along with the stereochemistry of reactions, chirality of some products, available types of functional groups, and their applications in designing unconventional drugs. This content is complemented with a report of the progress in physicochemical and biological studies on the parent cobalt bis(dicarbollide) ion and also includes an overview of recent syntheses and emerging applications of boron-substituted compounds. Full article

(This article belongs to the Special Issue New Developments in Boron Chemistry: From Oxidoborates to Hydrido(hetero)borane Derivatives – in Celebration of Professor John D. Kennedy’s 80th Birthday)

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20 pages, 6790 KiB

Open AccessEditor’s ChoiceArticle

Discovery of a SHP2 Degrader with In Vivo Anti-Tumor Activity

by Jinmin Miao, Yunpeng Bai, Yiming Miao, Zihan Qu, Jiajun Dong, Ruo-Yu Zhang, Devesh Aggarwal, Brenson A. Jassim, Quyen Nguyen and Zhong-Yin Zhang

Molecules 2023, 28(19), 6947; https://doi.org/10.3390/molecules28196947 - 6 Oct 2023

Cited by 5 | Viewed by 4000

Abstract

Src homology 2 domain-containing phosphatase 2 (SHP2) is an attractive target for cancer therapy due to its multifaceted roles in both tumor and immune cells. Herein, we designed and synthesized a novel series of proteolysis targeting chimeras (PROTACs) using a SHP2 allosteric inhibitor [...] Read more.

Src homology 2 domain-containing phosphatase 2 (SHP2) is an attractive target for cancer therapy due to its multifaceted roles in both tumor and immune cells. Herein, we designed and synthesized a novel series of proteolysis targeting chimeras (PROTACs) using a SHP2 allosteric inhibitor as warhead, with the goal of achieving SHP2 degradation both inside the cell and in vivo. Among these molecules, compound P9 induces efficient degradation of SHP2 (DC₅₀ = 35.2 ± 1.5 nM) in a concentration- and time-dependent manner. Mechanistic investigation illustrates that the P9-mediated SHP2 degradation requires the recruitment of the E3 ligase and is ubiquitination- and proteasome-dependent. P9 shows improved anti-tumor activity in a number of cancer cell lines over its parent allosteric inhibitor. Importantly, administration of P9 leads to a nearly complete tumor regression in a xenograft mouse model, as a result of robust SHP2 depletion and suppression of phospho-ERK1/2 in the tumor. Hence, P9 represents the first SHP2 PROTAC molecule with excellent in vivo efficacy. It is anticipated that P9 could serve not only as a new chemical tool to interrogate SHP2 biology but also as a starting point for the development of novel therapeutics targeting SHP2. Full article

(This article belongs to the Special Issue Small Molecules in Targeted Cancer Therapy)

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46 pages, 16647 KiB

Open AccessEditor’s ChoiceReview

Functionalized Calixarenes as Promising Antibacterial Drugs to Face Antimicrobial Resistance

by Maxime Mourer, Jean-Bernard Regnouf-de-Vains and Raphaël E. Duval

Molecules 2023, 28(19), 6954; https://doi.org/10.3390/molecules28196954 - 6 Oct 2023

Cited by 14 | Viewed by 3604

Abstract

Since the discovery of polyphenolic resins 150 years ago, the study of polymeric compounds named calix[n]arene has continued to progress, and those skilled in the art perfectly know now how to modulate this phenolic ring. Consequently, calix[n]arenes are now [...] Read more.

Since the discovery of polyphenolic resins 150 years ago, the study of polymeric compounds named calix[n]arene has continued to progress, and those skilled in the art perfectly know now how to modulate this phenolic ring. Consequently, calix[n]arenes are now used in a large range of applications and notably in therapeutic fields. In particular, the calix[4]arene exhibits multiple possibilities for regioselective polyfunctionalization on both of its rims and offers researchers the possibility of precisely tuning the geometry of their structures. Thus, in the crucial research of new antibacterial active ingredients, the design of calixarenes finds its place perfectly. This review provides an overview of the work carried out in this aim towards the development of intrinsically active prodrogues or metallic calixarene complexes. Out of all the work of the community, there are some excellent activities emerging that could potentially place these original structures in a very good position for the development of new active ingredients. Full article

(This article belongs to the Special Issue 150th Anniversary of the Creation of the Faculty of Pharmacy of Nancy, Université de Lorraine, France)

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16 pages, 3328 KiB

Open AccessEditor’s ChoiceArticle

Phenolic Compounds and Capsaicinoids in Three Capsicum annuum Varieties: From Analytical Characterization to In Silico Hypotheses on Biological Activity

by Deborah Giordano, Angelo Facchiano, Paola Minasi, Nunzio D’Agostino, Mario Parisi and Virginia Carbone

Molecules 2023, 28(19), 6772; https://doi.org/10.3390/molecules28196772 - 22 Sep 2023

Cited by 5 | Viewed by 2600

Abstract

The affinity of specific phenolic compounds (PCs) and capsaicinoids (CAPs) present in three Capsicum annuum varieties (Friariello, Cayenne and Dzuljunska Sipka) to the transient receptor potential vanilloid member 1 (TRPV1) was investigated by integrating an analytic approach for the simultaneous extraction and analysis [...] Read more.

The affinity of specific phenolic compounds (PCs) and capsaicinoids (CAPs) present in three Capsicum annuum varieties (Friariello, Cayenne and Dzuljunska Sipka) to the transient receptor potential vanilloid member 1 (TRPV1) was investigated by integrating an analytic approach for the simultaneous extraction and analysis through high-performance liquid chromatography coupled with ion trap mass spectrometry (HPLC/ITMS) and UV detection (HPLC-UV) of PCs and CAPs and structural bioinformatics based on the protein modelling and molecular simulations of protein–ligand docking. Overall, a total of 35 compounds were identified in the different samples and CAPs were quantified. The highest content of total polyphenols was recorded in the pungent Dzuljunska Sipka variety (8.91 ± 0.05 gGAE/Kg DW) while the lowest was found in the non-pungent variety Friariello (3.58 ± 0.02 gGAE/Kg DW). Protein modelling generated for the first time a complete model of the homotetrameric human TRPV1, and it was used for docking simulations with the compounds detected via the analytic approach, as well as with other compounds, as an inhibitor reference. The simulations indicate that different capsaicinoids can interact with the receptor, providing details on the molecular interaction, with similar predicted binding energy values. These results offer new insights into the interaction of capsaicinoids with TRPV1 and their possible actions. Full article

(This article belongs to the Special Issue Unveiling the Applications of Bioactive Compounds in Functional Foods for Optimal Human Health)

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22 pages, 5271 KiB

Open AccessEditor’s ChoiceArticle

Shikonin Causes an Apoptotic Effect on Human Kidney Cancer Cells through Ras/MAPK and PI3K/AKT Pathways

by József Király, Erzsébet Szabó, Petra Fodor, Zsolt Fejes, Béla Nagy, Jr., Éva Juhász, Anna Vass, Mahua Choudhury, Gábor Kónya, Gábor Halmos and Zsuzsanna Szabó

Molecules 2023, 28(18), 6725; https://doi.org/10.3390/molecules28186725 - 20 Sep 2023

Cited by 13 | Viewed by 2696

Abstract

(1) Background: Shikonin, the main ingredient in Chinese herbal medicine, is described as a novel angiogenesis inhibitor, and its anticancer effects have already been studied. Shikonin and its derivatives induce apoptosis and suppress metastasis, which further enhance the effectiveness of chemotherapy. However, their [...] Read more.

(1) Background: Shikonin, the main ingredient in Chinese herbal medicine, is described as a novel angiogenesis inhibitor, and its anticancer effects have already been studied. Shikonin and its derivatives induce apoptosis and suppress metastasis, which further enhance the effectiveness of chemotherapy. However, their mechanism of function has not been completely elucidated on human renal cancer cells. (2) Methods: In our study, CAKI-2 and A-498 cells were treated with increasing concentrations (2.5–40 µM) of shikonin, when colony formation ability and cytotoxic activity were tested. The changes in the expression of the main targets of apoptotic pathways were measured by RT-qPCR and Western blot. The intracellular levels of miR-21 and miR-155 were quantified by RT-qPCR. (3) Results: Shikonin exerted a dose-dependent effect on the proliferation of the cell lines examined. In 5 µM concentration of shikonin in vitro elevated caspase-3 and -7 levels, the proteins of the Ras/MAPK and PI3K/AKT pathways were activated. However, no significant changes were detected in the miR-21 and miR-155 expressions. (4) Conclusions: Our findings indicated that shikonin causes apoptosis of renal cancer cells by activating the Ras/MAPK and PI3K/AKT pathways. These effects of shikonin on renal cancer cells may bear important potential therapeutic implications for the treatment of renal cancer. Full article

(This article belongs to the Special Issue Natural Products Based Anticancer Drugs)

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19 pages, 2619 KiB

Open AccessEditor’s ChoiceArticle

Sustainable Recovery of Phenolic Compounds from Distilled Rosemary By-Product Using Green Extraction Methods: Optimization, Comparison, and Antioxidant Activity

by Maria Irakli, Adriana Skendi, Elisavet Bouloumpasi, Stamatia Christaki, Costas G. Biliaderis and Paschalina Chatzopoulou

Molecules 2023, 28(18), 6669; https://doi.org/10.3390/molecules28186669 - 17 Sep 2023

Cited by 24 | Viewed by 4442

Abstract

Rosemary solid distillation waste (SWR), a by-product of the essential oil industry, represents an important source of phenolic antioxidants. Green technologies such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and accelerated solvent extraction (ASE) of phenolic compounds from SWR were optimized as valorization [...] Read more.

Rosemary solid distillation waste (SWR), a by-product of the essential oil industry, represents an important source of phenolic antioxidants. Green technologies such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and accelerated solvent extraction (ASE) of phenolic compounds from SWR were optimized as valorization routes to maximize yield, rosmarinic acid (RMA), carnosol (CARO) and carnosic acid (CARA) contents. Response surface methodology was used in this context, with ethanol concentration (X₁), extraction temperature (X₂), and time (X₃) being the independent variables. A second-order polynomial model was fitted to the data, and multiple regression analysis and analysis of variance were used to determine model fitness and optimal conditions. Ethanol concentration was the most influential extraction parameter, affecting phenolic compounds, while the influence of other parameters was moderate. The optimized conditions were as follows: X₁: 67.4, 80.0, and 59.0%, X₂: 70, 51, and 125 °C, and X₃: 15, 10, and 7 min for MAE, UAE, and ASE, respectively. A comparison of optimized MAE, UAE, and ASE with conventional Soxhlet extraction techniques indicated that ASE provided a higher extraction yield and content of phenolic compounds. However, UAE represented the best process from an environmental point of view, allowing an improved extraction of phenolics from SWR with high energy efficiency and low energy costs. Full article

(This article belongs to the Special Issue Antioxidants from Natural Sources: Separation and Characterization Ⅱ)

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33 pages, 1804 KiB

Open AccessEditor’s ChoiceReview

A Review of the Effect of Plasticizers on the Physical and Mechanical Properties of Alginate-Based Films

by Zahra Eslami, Saïd Elkoun, Mathieu Robert and Kokou Adjallé

Molecules 2023, 28(18), 6637; https://doi.org/10.3390/molecules28186637 - 15 Sep 2023

Cited by 108 | Viewed by 11332

Abstract

In recent years, there has been a growing attempt to manipulate various properties of biodegradable materials to use them as alternatives to their synthetic plastic counterparts. Alginate is a polysaccharide extracted from seaweed or soil bacteria that is considered one of the most [...] Read more.

In recent years, there has been a growing attempt to manipulate various properties of biodegradable materials to use them as alternatives to their synthetic plastic counterparts. Alginate is a polysaccharide extracted from seaweed or soil bacteria that is considered one of the most promising materials for numerous applications. However, alginate potential for various applications is relatively limited due to brittleness, poor mechanical properties, scaling-up difficulties, and high water vapor permeability (WVP). Choosing an appropriate plasticizer can alleviate the situation by providing higher flexibility, workability, processability, and in some cases, higher hydrophobicity. This review paper discusses the main results and developments regarding the effects of various plasticizers on the properties of alginate-based films during the last decades. The plasticizers used for plasticizing alginate were classified into different categories, and their behavior under different concentrations and conditions was studied. Moreover, the drawback effects of plasticizers on the mechanical properties and WVP of the films are discussed. Finally, the role of plasticizers in the improved processing of alginate and the lack of knowledge on some aspects of plasticized alginate films is clarified, and accordingly, some recommendations for more classical studies of the plasticized alginate films in the future are offered. Full article

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10 pages, 2460 KiB

Open AccessEditor’s ChoiceArticle

Biocatalysis in Water or in Non-Conventional Media? Adding the CO₂ Production for the Debate

by Pablo Domínguez de María, Selin Kara and Fabrice Gallou

Molecules 2023, 28(18), 6452; https://doi.org/10.3390/molecules28186452 - 6 Sep 2023

Cited by 17 | Viewed by 2737

Abstract

Biocatalysis can be applied in aqueous media and in different non-aqueous solutions (non-conventional media). Water is a safe solvent, yet many synthesis-wise interesting substrates cannot be dissolved in aqueous solutions, and thus low concentrations are often applied. Conversely, non-conventional media may enable higher [...] Read more.

Biocatalysis can be applied in aqueous media and in different non-aqueous solutions (non-conventional media). Water is a safe solvent, yet many synthesis-wise interesting substrates cannot be dissolved in aqueous solutions, and thus low concentrations are often applied. Conversely, non-conventional media may enable higher substrate loadings but at the cost of using (fossil-based) organic solvents. This paper determines the CO₂ production—expressed as kg CO₂·kg product⁻¹—of generic biotransformations in water and non-conventional media, assessing both the upstream and the downstream. The key to reaching a diminished environmental footprint is the type of wastewater treatment to be implemented. If the used chemicals enable a conventional (mild) wastewater treatment, the production of CO₂ is limited. If other (pre)treatments for the wastewater are needed to eliminate hazardous chemicals and solvents, higher environmental impacts can be expected (based on CO₂ production). Water media for biocatalysis are more sustainable during the upstream unit—the biocatalytic step—than non-conventional systems. However, processes with aqueous media often need to incorporate extractive solvents during the downstream processing. Both strategies result in comparable CO₂ production if extractive solvents are recycled at least 1–2 times. Under these conditions, a generic industrial biotransformation at 100 g L⁻¹ loading would produce 15–25 kg CO₂·kg product⁻¹ regardless of the applied media. Full article

(This article belongs to the Special Issue Contribution of Enzyme Catalysis to the Achievement of the UN Sustainable Development Goals)

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13 pages, 767 KiB

Open AccessEditor’s ChoiceArticle

Inhibition of Enzymes Involved in Neurodegenerative Disorders and Aβ_1–40 Aggregation by Citrus limon Peel Polyphenol Extract

by Rosaria Arcone, Antonio D’Errico, Rosarita Nasso, Rosario Rullo, Annarita Poli, Paola Di Donato and Mariorosario Masullo

Molecules 2023, 28(17), 6332; https://doi.org/10.3390/molecules28176332 - 30 Aug 2023

Cited by 10 | Viewed by 2514

Abstract

Alzheimer’s (AD) and Parkinson’s diseases (PD) are multifactorial neurogenerative disorders of the Central Nervous System causing severe cognitive and motor deficits in elderly people. Because treatment of AD and PD by synthetic drugs alleviates the symptoms often inducing side effects, many studies have [...] Read more.

Alzheimer’s (AD) and Parkinson’s diseases (PD) are multifactorial neurogenerative disorders of the Central Nervous System causing severe cognitive and motor deficits in elderly people. Because treatment of AD and PD by synthetic drugs alleviates the symptoms often inducing side effects, many studies have aimed to find neuroprotective properties of diet polyphenols, compounds known to act on different cell signaling pathways. In this article, we analyzed the effect of polyphenols obtained from the agro-food industry waste of Citrus limon peel (LPE) on key enzymes of cholinergic and aminergic neurotransmission, such as butyryl cholinesterase (BuChE) and monoamine oxidases (MAO)-A/B, on Aβ_1–40 aggregation and on superoxide dismutase (SOD) 1/2 that affect oxidative stress. In our in vitro assays, LPE acts as an enzyme inhibitor on BuChE (IC₅₀ ~ 73 µM), MAO-A/B (IC₅₀ ~ 80 µM), SOD 1/2 (IC₅₀ ~ 10–20 µM) and interferes with Aβ_1–40 peptide aggregation (IC₅₀ ~ 170 µM). These results demonstrate that LPE behaves as a multitargeting agent against key factors of AD and PD by inhibiting to various extents BuChE, MAOs, and SODs and reducing Aβ-fibril aggregation. Therefore, LPE is a promising candidate for the prevention and management of AD and PD symptoms in combination with pharmacological therapies. Full article

(This article belongs to the Special Issue Bioactive Compounds for Brain Ischemia and Neurodegenerative Disease—Second Edition)

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34 pages, 5195 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Tinker, Tailor, Soldier, Spy: The Diverse Roles That Fluorine Can Play within Amino Acid Side Chains

by Samantha A. Miles, Joshua Andrew Nillama and Luke Hunter

Molecules 2023, 28(17), 6192; https://doi.org/10.3390/molecules28176192 - 22 Aug 2023

Cited by 11 | Viewed by 4458

Abstract

Side chain-fluorinated amino acids are useful tools in medicinal chemistry and protein science. In this review, we outline some general strategies for incorporating fluorine atom(s) into amino acid side chains and for elaborating such building blocks into more complex fluorinated peptides and proteins. [...] Read more.

Side chain-fluorinated amino acids are useful tools in medicinal chemistry and protein science. In this review, we outline some general strategies for incorporating fluorine atom(s) into amino acid side chains and for elaborating such building blocks into more complex fluorinated peptides and proteins. We then describe the diverse benefits that fluorine can offer when located within amino acid side chains, including enabling ¹⁹F NMR and ¹⁸F PET imaging applications, enhancing pharmacokinetic properties, controlling molecular conformation, and optimizing target-binding. Full article

(This article belongs to the Special Issue Feature Papers in Organic Chemistry (Volume II))

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13 pages, 2648 KiB

Open AccessEditor’s ChoiceArticle

Relationship between Chemical Structure and Biological Activity Evaluated In Vitro for Six Anthocyanidins Most Commonly Occurring in Edible Plants

by Izabela Koss-Mikołajczyk and Agnieszka Bartoszek

Molecules 2023, 28(16), 6156; https://doi.org/10.3390/molecules28166156 - 21 Aug 2023

Cited by 14 | Viewed by 3196

Abstract

Numerous studies have provided evidence that diets rich in anthocyanins show a broad spectrum of health benefits. Anthocyanins in nature are usually found in the form of glycosides. Their aglycone forms are called anthocyanidins. The chemical structure of anthocyanins is based on the [...] Read more.

Numerous studies have provided evidence that diets rich in anthocyanins show a broad spectrum of health benefits. Anthocyanins in nature are usually found in the form of glycosides. Their aglycone forms are called anthocyanidins. The chemical structure of anthocyanins is based on the flavylium cation, but they differ in the position and number of substituents. However, the bioactives and foods that contain them are frequently treated as a uniform group of compounds exhibiting the same biological activity, without paying attention to the structural differences between individual anthocyanidins. The aim of this study was to find out how structural differences impact the biological activity of the six most common dietary anthocyanidins, i.e., delphinidin (Dp), petunidin (Pt), cyanidin (Cd), malvidin (Mv), pelargonidin (Pg) and peonidin (Po). The study concentrated on redox-related phenomena and compared the following parameters: antioxidant activity (measured using various methods: spectrophotometric tests (ABTS, DPPH), ORAC assay and CAA test (cellular antioxidant activity)), the ability to inhibit growth of human colon cancer cells (HT29; determined using MTT assay), and the ability of studied compounds to protect DNA from oxidative damage (comet assay). Based on the obtained results, the relationship between the structure of studied anthocyanidins and their biological activity was assessed. The obtained results revealed that the number and position of the hydroxyl and methoxy groups in the anthocyanidin structure strongly influenced not only the color of anthocyanidins but most of all their antioxidant and biological activities. Full article

(This article belongs to the Special Issue Advances in Functional Foods)

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16 pages, 3142 KiB

Open AccessEditor’s ChoiceArticle

Structural Studies of Monounsaturated and ω-3 Polyunsaturated Free Fatty Acids in Solution with the Combined Use οf NMR and DFT Calculations—Comparison with the Liquid State

by Themistoklis Venianakis, Michael G. Siskos, George Papamokos and Ioannis P. Gerothanassis

Molecules 2023, 28(16), 6144; https://doi.org/10.3390/molecules28166144 - 20 Aug 2023

Cited by 5 | Viewed by 1777

Abstract

Molecular structures, in chloroform and DMSO solution, of the free fatty acids (FFAs) caproleic acid, oleic acid, α-linolenic acid, eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) are reported with the combined use of NMR and DFT calculations. Variable temperature and concentration chemical shifts [...] Read more.

Molecular structures, in chloroform and DMSO solution, of the free fatty acids (FFAs) caproleic acid, oleic acid, α-linolenic acid, eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) are reported with the combined use of NMR and DFT calculations. Variable temperature and concentration chemical shifts of the COOH protons, transient 1D NOE experiments and DFT calculations demonstrate the major contribution of low molecular weight aggregates of dimerized fatty acids through intermolecular hydrogen bond interactions of the carboxylic groups, with parallel and antiparallel interdigitated structures even at the low concentration of 20 mM in CDCl₃. For the dimeric DHA, a structural model of an intermolecular hydrogen bond through carboxylic groups and an intermolecular hydrogen bond between the carboxylic group of one molecule and the ω-3 double bond of a second molecule is shown to play a role. In DMSO-d₆ solution, NMR and DFT studies show that the carboxylic groups form strong intermolecular hydrogen bond interactions with a single discrete solvation molecule of DMSO. These solvation species form parallel and antiparallel interdigitated structures of low molecular weight, as in chloroform solution. This structural motif, therefore, is an intrinsic property of the FFAs, which is not strongly affected by the length and degree of unsaturation of the chain and the hydrogen bond ability of the solvent. Full article

(This article belongs to the Special Issue New Insights into Nuclear Magnetic Resonance (NMR) Spectroscopy)

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15 pages, 2717 KiB

Open AccessEditor’s ChoiceArticle

Multi-Functional Chitosan Nanovesicles Loaded with Bioactive Manganese for Potential Wound Healing Applications

by Edwin Davidson, Jorge Pereira, Giuliana Gan Giannelli, Zachary Murphy, Vasileios Anagnostopoulos and Swadeshmukul Santra

Molecules 2023, 28(16), 6098; https://doi.org/10.3390/molecules28166098 - 17 Aug 2023

Cited by 11 | Viewed by 2344

Abstract

Chronic skin wound is a chronic illness that possesses a risk of infection and sepsis. In particular, infections associated with antibiotic-resistant bacterial strains are challenging to treat. To combat this challenge, a suitable alternative that is complementary to antibiotics is desired for wound [...] Read more.

Chronic skin wound is a chronic illness that possesses a risk of infection and sepsis. In particular, infections associated with antibiotic-resistant bacterial strains are challenging to treat. To combat this challenge, a suitable alternative that is complementary to antibiotics is desired for wound healing. In this work, we report multi-functional nanoscale chitosan vesicles loaded with manganese (Chi-Mn) that has potential to serve as a new tool to augment traditional antibiotic treatment for skin wound healing. Chi-Mn showed antioxidant activity increase over time as well as antimicrobial activity against E. coli and P. aeruginosa PA01. The modified motility assay that mimicked a skin wound before bacterial colonization showed inhibition of bacterial growth with Chi-Mn treatment at a low area density of 0.04 µg of Mn per cm². Furthermore, this study demonstrated the compatibility of Chi-Mn with a commercial antibiotic showing no loss of antimicrobial potency. In vitro cytotoxicity of Chi-Mn was assessed with macrophages and dermal cell lines (J774A.1 and HDF) elucidating biocompatibility at a wide range (2 ppm–256 ppm). A scratch wound assay involving human dermal fibroblast (HDF) cells was performed to assess any negative effect of Chi-Mn on cell migration. Confocal microscopy study confirmed that Chi-Mn tested at the MIC (16 ppm Mn) has no effect on cell migration with respect to control. Overall, this study demonstrated the potential of Chi-Mn nanovesicles for wound healing applications. Full article

(This article belongs to the Special Issue Chitosan, Chitosan Derivatives and Their Applications)

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22 pages, 783 KiB

Open AccessEditor’s ChoiceReview

Malondialdehyde as a Potential Oxidative Stress Marker for Allergy-Oriented Diseases: An Update

by Raffaele Cordiano, Mario Di Gioacchino, Rocco Mangifesta, Claudia Panzera, Sebastiano Gangemi and Paola Lucia Minciullo

Molecules 2023, 28(16), 5979; https://doi.org/10.3390/molecules28165979 - 9 Aug 2023

Cited by 164 | Viewed by 25376

Abstract

Malondialdehyde (MDA) is a compound that is derived from the peroxidation of polyunsaturated fatty acids. It has been used as a biomarker to measure oxidative stress in various biological samples in patients who are affected by a wide range of diseases. The aim [...] Read more.

Malondialdehyde (MDA) is a compound that is derived from the peroxidation of polyunsaturated fatty acids. It has been used as a biomarker to measure oxidative stress in various biological samples in patients who are affected by a wide range of diseases. The aim of our work is to provide an updated overview of the role of MDA as a marker of oxidative stress in allergy-related diseases. We considered studies involving both paediatric and adult patients affected by rhinitis, asthma, urticaria and atopic dermatitis. The measurement of MDA was performed on different types of samples. The reported data highlight the role of serum MDA in inflammatory airway diseases. According to the literature review, the oxidative stress status in asthmatic patients, assessed via MDA determination, appears to worsen in the presence of other allergic airway diseases and in relation to the disease severity. This suggests that MDA can be a suitable marker for monitoring the disease status. However, there are several limitations in the considered studies due to the different samples used and the lack of phenotyping and description of the clinical period of patients examined. In cutaneous allergic diseases, the role of MDA is controversial because of the smallness of the studies and the heterogeneity of the samples and patients. Full article

(This article belongs to the Special Issue Chemistry, Biology and Pharmacology of Modulators of Oxidative Stress)

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22 pages, 1219 KiB

Open AccessEditor’s ChoiceReview

Advancements in Sustainable Natural Dyes for Textile Applications: A Review

by Barbara Pizzicato, Severina Pacifico, Diana Cayuela, Gabriela Mijas and Marta Riba-Moliner

Molecules 2023, 28(16), 5954; https://doi.org/10.3390/molecules28165954 - 8 Aug 2023

Cited by 101 | Viewed by 29695

Abstract

The dyeing and finishing step represents a clear hotspot in the textile supply chain as the wet processing stages require significant amounts of water, energy, and chemicals. In order to tackle environmental issues, natural dyes are gaining attention from researchers as more sustainable [...] Read more.

The dyeing and finishing step represents a clear hotspot in the textile supply chain as the wet processing stages require significant amounts of water, energy, and chemicals. In order to tackle environmental issues, natural dyes are gaining attention from researchers as more sustainable alternatives to synthetic ones. This review discusses the topic of natural dyes, providing a description of their main features and differences compared to synthetic dyes, and encompasses a summary of recent research in the field of natural dyes with specific reference to the following areas of sustainable innovation: extraction techniques, the preparation of substrates, the mordanting process, and the dyeing process. The literature review showed that promising new technologies and techniques have been successfully employed to improve the performance and sustainability of natural dyeing processes, but several limitations such as the poor fastness properties of natural dyes, their low affinity with textiles substrates, difficulties in the reproducibility of shades, as well as other factors such as cost-effectiveness considerations, still prevent industry from adopting natural dyes on a larger scale and will require further research in order to expand their use beyond niche applications. Full article

(This article belongs to the Section Colorants)

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16 pages, 1553 KiB

Open AccessEditor’s ChoiceReview

Amanitins: The Most Poisonous Molecules of the Fungal World

by János Vetter

Molecules 2023, 28(15), 5932; https://doi.org/10.3390/molecules28155932 - 7 Aug 2023

Cited by 16 | Viewed by 5765

Abstract

Among the toxic metabolites of the fungal world, those that, due to their strong biological effect, can seriously (even fatally) damage the life processes of humans (and certain groups of animals) stand out. Amatoxin-containing mushrooms and the poisonings caused by them stand out [...] Read more.

Among the toxic metabolites of the fungal world, those that, due to their strong biological effect, can seriously (even fatally) damage the life processes of humans (and certain groups of animals) stand out. Amatoxin-containing mushrooms and the poisonings caused by them stand out from the higher fungi, the mushrooms. There are already historical data and records about such poisonings, but scientific research on the responsible molecules began in the middle of the last century. The goals of this review work are as follows: presentation of the cosmopolitan mushroom species that produce amanitins (which are known from certain genera of four mushroom families), an overview of the chemical structure and specific properties of amanitins, a summary of the analytical methods applicable to them, a presentation of the “medical history” of poisonings, and a summary of the therapeutic methods used so far. The main responsible molecules (the amanitins) are bicyclic octapeptides, whose structure is characterized by an outer loop and an inner loop (bridge). It follows from the unusual properties of amanitins, especially their extreme stability (against heat, the acidic pH of the medium, and their resistance to human, and animal, digestive enzymes), that they are absorbed almost without hindrance and quickly transported to our vital organs. Adding to the problems is that accidental consumption causes no noticeable symptoms for a few hours (or even 24–36 h) after consumption, but the toxins already damage the metabolism of the target organs and the synthesis of nucleic acid and proteins. The biochemical catastrophe of the cells causes irreversible structural changes, which lead to necrotic damage (in the liver and kidneys) and death. The scientific topicality of the review is due to the recent publication of new data on the probable antidote molecule (ICR: indocyanine green) against amanitins. Further research can provide a new foundation for the therapeutic treatment of poisonings, and the toxicological situation, which currently still poses a deadly threat, could even be tamed into a controllable problem. We also draw attention to the review conclusions, as well as the mycological and social tasks related to amanitin poisonings (prevention of poisonings). Full article

(This article belongs to the Special Issue Natural Substances and Their Derivatives: In Search of New Structures, Activities and Applications)

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16 pages, 4332 KiB

Open AccessEditor’s ChoiceArticle

Optimisation of Polyphenols Extraction from Wild Bilberry Leaves—Antimicrobial Properties and Stability Studies

by Ana-Maria Brezoiu, Mihaela Deaconu, Raul-Augustin Mitran, Ana-Maria Prelipcean, Cristian Matei and Daniela Berger

Molecules 2023, 28(15), 5795; https://doi.org/10.3390/molecules28155795 - 1 Aug 2023

Cited by 7 | Viewed by 1678

Abstract

Polyphenolic extracts from natural sources have received great interest due to their beneficial properties for human health. A method to reduce their variability is to use the design of experiments which allows a limited number of experiments to be performed while exploring the [...] Read more.

Polyphenolic extracts from natural sources have received great interest due to their beneficial properties for human health. A method to reduce their variability is to use the design of experiments which allows a limited number of experiments to be performed while exploring the experimental space. Firstly, a 2³-full factorial model was used to investigate the polyphenols extraction from wild bilberry leaves. Spectrophotometric data (the content of polyphenols, flavonoids, chlorophyll and radical scavenger activity) and extraction yield were used as responses, and six statistical models were determined depending on the two numerical factors (temperature and alcohol % of ethanol–water mixture) being significant (p < 0.05) in all cases. Numerical optimisation performed by Design Expert 13 software correlates well with the chemical profile determined by high-performance liquid chromatography and the amount of the polyphenol. Afterwards, under the optimised conditions, an extract was prepared in three extraction steps for which composition, chemical stability and antimicrobial properties were evaluated. The antimicrobial potential of the extract was compared with that of the standard compounds (rutin and chlorogenic acid), and the results supported a synergistic effect of the extract components. Full article

(This article belongs to the Section Food Chemistry)

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36 pages, 10158 KiB

Open AccessEditor’s ChoiceReview

Significance of Five-Membered Heterocycles in Human Histone Deacetylase Inhibitors

by Anton Frühauf, Martin Behringer and Franz-Josef Meyer-Almes

Molecules 2023, 28(15), 5686; https://doi.org/10.3390/molecules28155686 - 27 Jul 2023

Cited by 15 | Viewed by 3637

Abstract

Five-membered heteroaromatic rings, in particular, have gained prominence in medicinal chemistry as they offer enhanced metabolic stability, solubility and bioavailability, crucial factors in developing effective drugs. The unique physicochemical properties and biological effects of five-membered heterocycles have positioned them as key structural motifs [...] Read more.

Five-membered heteroaromatic rings, in particular, have gained prominence in medicinal chemistry as they offer enhanced metabolic stability, solubility and bioavailability, crucial factors in developing effective drugs. The unique physicochemical properties and biological effects of five-membered heterocycles have positioned them as key structural motifs in numerous clinically effective drugs. Hence, the exploration of five-ring heterocycles remains an important research area in medicinal chemistry, with the aim of discovering new therapeutic agents for various diseases. This review addresses the incorporation of heteroatoms such as nitrogen, oxygen and sulfur into the aromatic ring of these heterocyclic compounds, enhancing their polarity and facilitating both aromatic stacking interactions and the formation of hydrogen bonds. Histone deacetylases are present in numerous multiprotein complexes within the epigenetic machinery and play a central role in various cellular processes. They have emerged as important targets for cancer, neurodegenerative diseases and other therapeutic indications. In histone deacetylase inhibitors (HDACi’s), five-ring heterocycles perform various functions as a zinc-binding group, a linker or head group, contributing to binding activity and selective recognition. This review focuses on providing an up-to-date overview of the different five-membered heterocycles utilized in HDACi motifs, highlighting their biological properties. It summarizes relevant publications from the past decade, offering insights into the recent advancements in this field of research. Full article

(This article belongs to the Special Issue Advances in Synthesis and Biological Activity of Novel Derivatives Based on Five-Membered Heterocyclic Scaffolds and Their Intermediates)

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10 pages, 678 KiB

Open AccessEditor’s ChoiceArticle

Arabinoxylan from Corn Fiber Obtained through Alkaline Extraction and Membrane Purification: Relating Bioactivities with the Phenolic Compounds

by Verónica Weng, Martim Cardeira, Andreia Bento-Silva, Ana Teresa Serra, Carla Brazinha and Maria Rosário Bronze

Molecules 2023, 28(15), 5621; https://doi.org/10.3390/molecules28155621 - 25 Jul 2023

Cited by 9 | Viewed by 2258

Abstract

Arabinoxylan has prebiotic properties, as it is able to resist digestion in the small intestine and undergoes fermentation in the large intestine. In this work, arabinoxylan was extracted from corn fiber using an alkaline solution and further purified with membrane processing. It was [...] Read more.

Arabinoxylan has prebiotic properties, as it is able to resist digestion in the small intestine and undergoes fermentation in the large intestine. In this work, arabinoxylan was extracted from corn fiber using an alkaline solution and further purified with membrane processing. It was found that the extracts were mainly composed of xylose (50–52%), arabinose (37–39%), galactose (9%) and glucose (1–4%), with an A/X ratio of 0.72–0.77. All the extracts were composed of phenolic compounds, including ferulic acid derivatives such as dimers, trimers and tetramers. The purified extract had a lower concentration of ferulic and p-coumaric acid (0.004 and 0.02 mg/mg_{dry_weight}, respectively) when compared to raw extract (19.30 and 2.74 mg/mg_{dry_weight}, respectively). The same effect was observed for the antioxidant activity, with purified extracts having a lower value (0.17 ± 0.02 µmol TEAC/mg) when compared to the raw extract (2.20 ± 0.35 µmol TEAC/mg). The purified extract showed a greater antiproliferative effect against the HT29 cell line with EC₅₀ = 0.12 ± 0.02 mg/mL when compared to the raw extract (EC₅₀ = 5.60 ± 1.6 mg/mL). Both raw and purified extracts did not show any cytotoxicity to the Caco-2 cell line in the maximum concentration tested (10 mg/mL). Full article

(This article belongs to the Special Issue Green Chemistry in Portugal)

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16 pages, 2245 KiB

Open AccessEditor’s ChoiceArticle

Synthesis and Biological Evaluation of Resveratrol Methoxy Derivatives

by Elizabeth Fragopoulou, Katerina Gkotsi, Filio Petsini, Katerina Gioti, Amalia D. Kalampaliki, George Lambrinidis, Ioannis K. Kostakis and Roxane Tenta

Molecules 2023, 28(14), 5547; https://doi.org/10.3390/molecules28145547 - 20 Jul 2023

Cited by 14 | Viewed by 2760

Abstract

Resveratrol, a naturally occurring stilbene, exhibits numerous beneficial health effects. Various studies have demonstrated its diverse biological actions, including anti-oxidant, anti-inflammatory, and anti-platelet properties, thereby supporting its potential for cardio protection, neuroprotection, and anti-cancer activity. However, a significant limitation of resveratrol is its [...] Read more.

Resveratrol, a naturally occurring stilbene, exhibits numerous beneficial health effects. Various studies have demonstrated its diverse biological actions, including anti-oxidant, anti-inflammatory, and anti-platelet properties, thereby supporting its potential for cardio protection, neuroprotection, and anti-cancer activity. However, a significant limitation of resveratrol is its weak bioavailability. To overcome this challenge, multiple research groups have investigated the synthesis of new resveratrol derivatives to enhance bioavailability and pharmacological activities. Nevertheless, there are limited data on the effects of resveratrol derivatives on platelet function. Therefore, the objective of this study was to synthesize resveratrol methoxy derivatives and evaluate their anti-platelet and anti-proliferative activity. Platelet-rich plasma (PRP) obtained from healthy volunteers was utilized to assess the derivatives’ ability to inhibit platelet aggregation induced by platelet activating factor (PAF), adenosine diphosphate (ADP), and thrombin receptor activating peptide (TRAP). Additionally, the derivatives’ anti-tumor activity was evaluated against the proliferation of PC-3 and HCT116 cells. The results revealed that some methoxy derivatives of resveratrol exhibited comparable or even superior anti-platelet activity compared to the original compound. The most potent derivative was the 4′-methoxy derivative, which demonstrated approximately 2.5 orders of magnitude higher anti-platelet activity against TRAP-induced platelet aggregation, indicating its potential as an anti-platelet agent. Concerning in silico studies, the 4′-methyl group of 4′-methoxy derivative is oriented similarly to the fluorophenyl–pyridyl group of Vorapaxar, buried in a hydrophobic cavity. In terms of their anti-tumor activity, 3-MRESV exhibited the highest potency in PC-3 cells, while 3,4′-DMRESV and TMRESV showed the greatest efficacy in HCT116 cells. In conclusion, methoxy derivatives of resveratrol possess similar or improved anti-platelet and anti-cancer effects, thereby holding potential as bioactive compounds in various pathological conditions. Full article

(This article belongs to the Section Medicinal Chemistry)

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15 pages, 2417 KiB

Open AccessEditor’s ChoiceArticle

Supercritical Fluid Extraction (SFE) of Polar Compounds from Camellia sinensis Leaves: Use of Ethanol/Water as a Green Polarity Modifier

by Sirine Atwi-Ghaddar, Lydie Zerwette, Emilie Destandau and Eric Lesellier

Molecules 2023, 28(14), 5485; https://doi.org/10.3390/molecules28145485 - 18 Jul 2023

Cited by 25 | Viewed by 3740

Abstract

The use of bioactive plant extracts in cosmetic products is a common practice. Most of these extracts are obtained by maceration in organic solvents, and depending on which solvents are used, the polarity and the structure of the target molecules will vary. Polyphenols [...] Read more.

The use of bioactive plant extracts in cosmetic products is a common practice. Most of these extracts are obtained by maceration in organic solvents, and depending on which solvents are used, the polarity and the structure of the target molecules will vary. Polyphenols are polar compounds that often display antioxidant and/or antibacterial activities. To extract them, ethanol/water mixtures are usually selected as green solvents. This solid–liquid extraction (assisted or not) requires the use of high volumes of solvents and many additional steps like mixing, agitation, filtration, and evaporation. Alternatively, supercritical carbon dioxide (SC-CO₂) offers many benefits for plant extraction: economical, non-toxic, and naturally concentrated extracts. However, its low polarity is not suitable to solubilize polar compounds. In this study, an experimental design was used to optimize supercritical fluid extraction (SFE) of caffeine and catechins from Camellia sinensis. Catechins are recognized for skin care use (antioxidant) and caffeine is also used for its skin care properties and to prevent excess storage of fat in cells. The temperature, modifier content, and water additive percentage were used as independent variables. The results showed that while the temperature was an insignificant parameter, a higher percentage of water (up to 20% in ethanol) and modifier favored the extraction of the polar target molecules. Additionally, the SFE results were compared with ultrasound-assisted extraction (UAE). Finally, a sequential selective extraction of caffeine from catechins is also presented. Full article

(This article belongs to the Special Issue Recent Development in Subcritical Water Extraction and Chromatography)

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18 pages, 3328 KiB

Open AccessEditor’s ChoiceArticle

Understanding the Mechanism for Adsorption of Pb(II) Ions by Cu-BTC Metal–Organic Frameworks

by Joanna N. Weyrich, John R. Mason, Ekaterina A. Bazilevskaya and Hongwei Yang

Molecules 2023, 28(14), 5443; https://doi.org/10.3390/molecules28145443 - 16 Jul 2023

Cited by 14 | Viewed by 3654

Abstract

With the growing population, industrialization, and agriculture, water contamination not only affects people but entire ecosystems. Metal–organic frameworks (MOFs), because of their large surface area and porosity, show great potential as adsorbents for removing pollutants, such as heavy metals, from contaminated water. The [...] Read more.

With the growing population, industrialization, and agriculture, water contamination not only affects people but entire ecosystems. Metal–organic frameworks (MOFs), because of their large surface area and porosity, show great potential as adsorbents for removing pollutants, such as heavy metals, from contaminated water. The current research aims at examining copper (II) benzene-1,3,5-tricarboxylate (Cu-BTC) MOFs and understanding the mechanism for their adsorption of Pb(II) from aqueous solution. The Cu-BTC samples were characterized using FTIR and XRD, and their surface area and porosity were determined based on N₂ adsorption isotherms. The concentration of Pb(II) in the solutions was measured using atomic absorption spectroscopy (AAS). Both kinetic and equilibrium adsorption data were collected and then analyzed using numerical models. The analyses led to the findings that the limiting steps in the adsorption of Pb(II) on Cu-BTC are (a) pore diffusion of Pb(II) and (b) the availability of the active sites on Cu-BTC MOFs. It was further revealed that the former step is more dominant in the adsorption of Pb(II) when the lead concentration is low. The latter step, which is directly proportional to the surface areas of the MOFs, affects the adsorption to a greater extent when the lead concentration is high. The results also show that adsorption of Pb(II) ions on Cu-BTC is mainly a multi-layer heterogeneous process. Full article

(This article belongs to the Special Issue Wastewater Treatment: Functional Materials and Advanced Technology)

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