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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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30 pages, 1381 KiB  
Review
Deep Eutectic Solvents: Properties and Applications in CO2 Separation
by Iwona Cichowska-Kopczyńska, Bartosz Nowosielski and Dorota Warmińska
Molecules 2023, 28(14), 5293; https://doi.org/10.3390/molecules28145293 - 8 Jul 2023
Cited by 52 | Viewed by 9871
Abstract
Nowadays, many researchers are focused on finding a solution to the problem of global warming. Carbon dioxide is considered to be responsible for the “greenhouse” effect. The largest global emission of industrial CO2 comes from fossil fuel combustion, which makes power plants [...] Read more.
Nowadays, many researchers are focused on finding a solution to the problem of global warming. Carbon dioxide is considered to be responsible for the “greenhouse” effect. The largest global emission of industrial CO2 comes from fossil fuel combustion, which makes power plants the perfect point source targets for immediate CO2 emission reductions. A state-of-the-art method for capturing carbon dioxide is chemical absorption using an aqueous solution of alkanolamines, most frequently a 30% wt. solution of monoethanolamine (MEA). Unfortunately, the usage of alkanolamines has a number of drawbacks, such as the corrosive nature of the reaction environment, the loss of the solvent due to its volatility, and a high energy demand at the regeneration step. These problems have driven the search for alternatives to that method, and deep eutectic solvents (DESs) might be a very good substitute. Many types of DESs have thus far been investigated for efficient CO2 capture, and various hydrogen bond donors and acceptors have been used. Deep eutectic solvents that are capable of absorbing carbon dioxide physically and chemically have been reported. Strategies for further CO2 absorption improvement, such as the addition of water, other co-solvents, or metal salts, have been proposed. Within this review, the physical properties of DESs are presented, and their effects on CO2 absorption capacity are discussed in conjunction with the types of HBAs and HBDs and their molar ratios. The practical issues of using DESs for CO2 separation are also described. Full article
(This article belongs to the Special Issue Deep Eutectic Solvents: Properties and Applications as Green Solvents)
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35 pages, 512 KiB  
Review
Recent Advances in Deep Learning for Protein-Protein Interaction Analysis: A Comprehensive Review
by Minhyeok Lee
Molecules 2023, 28(13), 5169; https://doi.org/10.3390/molecules28135169 - 2 Jul 2023
Cited by 43 | Viewed by 10275
Abstract
Deep learning, a potent branch of artificial intelligence, is steadily leaving its transformative imprint across multiple disciplines. Within computational biology, it is expediting progress in the understanding of Protein–Protein Interactions (PPIs), key components governing a wide array of biological functionalities. Hence, an in-depth [...] Read more.
Deep learning, a potent branch of artificial intelligence, is steadily leaving its transformative imprint across multiple disciplines. Within computational biology, it is expediting progress in the understanding of Protein–Protein Interactions (PPIs), key components governing a wide array of biological functionalities. Hence, an in-depth exploration of PPIs is crucial for decoding the intricate biological system dynamics and unveiling potential avenues for therapeutic interventions. As the deployment of deep learning techniques in PPI analysis proliferates at an accelerated pace, there exists an immediate demand for an exhaustive review that encapsulates and critically assesses these novel developments. Addressing this requirement, this review offers a detailed analysis of the literature from 2021 to 2023, highlighting the cutting-edge deep learning methodologies harnessed for PPI analysis. Thus, this review stands as a crucial reference for researchers in the discipline, presenting an overview of the recent studies in the field. This consolidation helps elucidate the dynamic paradigm of PPI analysis, the evolution of deep learning techniques, and their interdependent dynamics. This scrutiny is expected to serve as a vital aid for researchers, both well-established and newcomers, assisting them in maneuvering the rapidly shifting terrain of deep learning applications in PPI analysis. Full article
(This article belongs to the Special Issue Recent Progress for Structure and Function Prediction of Protein and RNA)
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17 pages, 9815 KiB  
Article
Salicylic Acid Release from Syndiotactic Polystyrene Staple Fibers
by Verdiana Covelli, Antonietta Cozzolino, Paola Rizzo, Manuela Rodriquez, Vincenzo Vestuto, Alessia Bertamino, Christophe Daniel and Gaetano Guerra
Molecules 2023, 28(13), 5095; https://doi.org/10.3390/molecules28135095 - 29 Jun 2023
Cited by 13 | Viewed by 2322
Abstract
Films and fibers of syndiotactic polystyrene (sPS), being amorphous or exhibiting nanoporous crystalline (NC) or dense crystalline phases, were loaded with salicylic acid (SA), a relevant non-volatile antimicrobial molecule. In the first section of the paper, sPS/SA co-crystalline (CC) δ form is characterized, [...] Read more.
Films and fibers of syndiotactic polystyrene (sPS), being amorphous or exhibiting nanoporous crystalline (NC) or dense crystalline phases, were loaded with salicylic acid (SA), a relevant non-volatile antimicrobial molecule. In the first section of the paper, sPS/SA co-crystalline (CC) δ form is characterized, mainly by wide angle X-ray diffraction (WAXD) patterns and polarized Fourier transform infrared (FTIR) spectra. The formation of sPS/SA δ CC phases allows the preparation of sPS fibers even with a high content of the antibacterial guest, which is also retained after repeated washing procedures at 65 °C. A preparation procedure starting from amorphous fibers is particularly appropriate because involves a direct formation of the CC δ form and a simultaneous axial orientation. The possibility of tuning drug amount and release kinetics, by simply selecting suitable crystalline phases of a commercially available polymer, makes sPS fibers possibly useful for many applications. In particular, fibers with δ CC forms, which retain SA molecules in their crystalline phases, could be useful for antimicrobial textiles and fabrics. Fibers with the dense γ form which easily release SA molecules, because they are only included in their amorphous phases, could be used for promising SA-based preparations for antibacterial purposes in food processing and preservation and public health. Finally, using a cell-based assay system and antibacterial tests, we investigated the cellular activity, toxicity and antimicrobial properties of amorphous, δ CC forms and dense γ form of sPS fibers loaded with different contents of SA. Full article
(This article belongs to the Special Issue Nanofibers and Nanotextured Materials: Their Multipurpose Applications)
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42 pages, 5338 KiB  
Review
Photodynamic Therapy: From the Basics to the Current Progress of N-Heterocyclic-Bearing Dyes as Effective Photosensitizers
by Eurico Lima and Lucinda V. Reis
Molecules 2023, 28(13), 5092; https://doi.org/10.3390/molecules28135092 - 29 Jun 2023
Cited by 41 | Viewed by 7431
Abstract
Photodynamic therapy, an alternative that has gained weight and popularity compared to current conventional therapies in the treatment of cancer, is a minimally invasive therapeutic strategy that generally results from the simultaneous action of three factors: a molecule with high sensitivity to light, [...] Read more.
Photodynamic therapy, an alternative that has gained weight and popularity compared to current conventional therapies in the treatment of cancer, is a minimally invasive therapeutic strategy that generally results from the simultaneous action of three factors: a molecule with high sensitivity to light, the photosensitizer, molecular oxygen in the triplet state, and light energy. There is much to be said about each of these three elements; however, the efficacy of the photosensitizer is the most determining factor for the success of this therapeutic modality. Porphyrins, chlorins, phthalocyanines, boron-dipyrromethenes, and cyanines are some of the N-heterocycle-bearing dyes’ classes with high biological promise. In this review, a concise approach is taken to these and other families of potential photosensitizers and the molecular modifications that have recently appeared in the literature within the scope of their photodynamic application, as well as how these compounds and their formulations may eventually overcome the deficiencies of the molecules currently clinically used and revolutionize the therapies to eradicate or delay the growth of tumor cells. Full article
(This article belongs to the Special Issue Recent Developments in the Synthesis and Functionalization of Nitrogen Heterocycles)
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16 pages, 2234 KiB  
Review
Protein-Based Hydrogels and Their Biomedical Applications
by Kok Zhi Lee, Juya Jeon, Bojing Jiang, Shri Venkatesh Subramani, Jingyao Li and Fuzhong Zhang
Molecules 2023, 28(13), 4988; https://doi.org/10.3390/molecules28134988 - 25 Jun 2023
Cited by 35 | Viewed by 9180
Abstract
Hydrogels made from proteins are attractive materials for diverse medical applications, as they are biocompatible, biodegradable, and amenable to chemical and biological modifications. Recent advances in protein engineering, synthetic biology, and material science have enabled the fine-tuning of protein sequences, hydrogel structures, and [...] Read more.
Hydrogels made from proteins are attractive materials for diverse medical applications, as they are biocompatible, biodegradable, and amenable to chemical and biological modifications. Recent advances in protein engineering, synthetic biology, and material science have enabled the fine-tuning of protein sequences, hydrogel structures, and hydrogel mechanical properties, allowing for a broad range of biomedical applications using protein hydrogels. This article reviews recent progresses on protein hydrogels with special focus on those made of microbially produced proteins. We discuss different hydrogel formation strategies and their associated hydrogel properties. We also review various biomedical applications, categorized by the origin of protein sequences. Lastly, current challenges and future opportunities in engineering protein-based hydrogels are discussed. We hope this review will inspire new ideas in material innovation, leading to advanced protein hydrogels with desirable properties for a wide range of biomedical applications. Full article
(This article belongs to the Special Issue Structure and Dynamics of Polymers and Self-Assembled Soft Materials)
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12 pages, 4735 KiB  
Article
Cysteine Redox Chemistry in Peptide Self-Assembly to Modulate Hydrogelation
by Maria Cristina Cringoli and Silvia Marchesan
Molecules 2023, 28(13), 4970; https://doi.org/10.3390/molecules28134970 - 24 Jun 2023
Cited by 7 | Viewed by 3045
Abstract
Cysteine redox chemistry is widely used in nature to direct protein assembly, and in recent years it has inspired chemists to design self-assembling peptides too. In this concise review, we describe the progress in the field focusing on the recent advancements that make [...] Read more.
Cysteine redox chemistry is widely used in nature to direct protein assembly, and in recent years it has inspired chemists to design self-assembling peptides too. In this concise review, we describe the progress in the field focusing on the recent advancements that make use of Cys thiol–disulfide redox chemistry to modulate hydrogelation of various peptide classes. Full article
(This article belongs to the Special Issue Peptide-Based Supramolecular Materials)
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17 pages, 383 KiB  
Review
Effects of Short- and Medium-Chain Fatty Acids on Production, Meat Quality, and Microbial Attributes—A Review
by Rubina Tünde Szabó, Mária Kovács-Weber, Ágnes Zimborán, Levente Kovács and Márta Erdélyi
Molecules 2023, 28(13), 4956; https://doi.org/10.3390/molecules28134956 - 23 Jun 2023
Cited by 26 | Viewed by 4121
Abstract
The non-therapeutic use of antimicrobials in poultry production contributes to the spread of drug-resistant pathogens in both birds and humans. Antibiotics are known to enhance feed efficiency and promote the growth and weight gain of poultry. New regulatory requirements and consumer preferences have [...] Read more.
The non-therapeutic use of antimicrobials in poultry production contributes to the spread of drug-resistant pathogens in both birds and humans. Antibiotics are known to enhance feed efficiency and promote the growth and weight gain of poultry. New regulatory requirements and consumer preferences have led to a reduced use of antibiotics in poultry production and to the discovery of natural alternatives to antibiotic growth promoters. This interest is not only focused on the direct removal or inhibition of causative microorganisms but also on the prevention of diseases caused by enteric pathogens using a range of feed additives. A group of promising feed additives is composed of short- and medium-chain fatty acids (SCFAs and MCFAs) and their derivatives. MCFAs possess antibacterial, anticoccidial, and antiviral effects. In addition, it has been proven that these acids act in synergy if they are used together with organic acids, essential oils, or probiotics. These fatty acids also benefit intestinal health integrity and homeostasis in broilers. Other effects have been documented as well, such as an increase in intestinal angiogenesis and the gene expression of tight junctions. The aim of this review is to provide an overview of SCFAs and MCFAs as alternatives to antibiotic growth promoters and to summarize the current findings in the literature to show their possible benefits on production, meat quality, and gut health in poultry. Full article
(This article belongs to the Special Issue Feature Papers in Food Chemistry—2nd Edition)
16 pages, 1390 KiB  
Article
Characterization of Antioxidant and Antimicrobial Activity and Phenolic Compound Profile of Extracts from Seeds of Different Vitis Species
by Luisa Pozzo, Teresa Grande, Andrea Raffaelli, Vincenzo Longo, Stanisław Weidner, Ryszard Amarowicz and Magdalena Karamać
Molecules 2023, 28(13), 4924; https://doi.org/10.3390/molecules28134924 - 22 Jun 2023
Cited by 19 | Viewed by 3446
Abstract
Seeds of Vitis vinifera L. with a high content of bioactive compounds are valuable by-products from grape processing. However, little is known about the bioactivity of seeds from other Vitis species. The aim of this study has been to compare the phenolic composition, [...] Read more.
Seeds of Vitis vinifera L. with a high content of bioactive compounds are valuable by-products from grape processing. However, little is known about the bioactivity of seeds from other Vitis species. The aim of this study has been to compare the phenolic composition, antimicrobial activity, and antioxidant activity of extracts from seeds of four Vitis species (V. riparia Michx., V. californica Benth., V. amurensis Rupr., and V. vinifera L.). Antioxidant activities were assessed as ferric-reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) scavenging activity, and oxygen radical absorbance capacity (ORAC). The antimicrobial activity was determined using the microdilution method against some Gram-negative (Escherichia coli, Salmonella enterica ser. Typhimurium, and Enterobacter aerogenes) and Gram-positive (Enterococcus faecalis and Staphylococcus aureus) bacteria. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to evaluate the phenolic profile of extracts. Flavan-3-ols, procyanidins, phenolic acids, flavonols, anthocyanins, and stilbenoids were detected. (+)-Catechin and (−)-epicatechin turned out to be the most abundant in the phenolic profile of V. amurensis seed extract. Phenolic acids prevailed in the extract from V. vinifera seeds. The V. riparia and V. californica seed extracts had higher contents of most individual phenolics compared to the other Vitis species. They also showed a higher total phenolic content, DPPH• scavenging activity, ORAC, and overall antibacterial activity. Total phenolic content significantly correlated with antioxidant activity and antimicrobial activity against E. coli. The principal component analysis (PCA) showed discrimination between V. vinifera, V. amurensis, and clustered V. riparia and V. californica with respect to variables. To recapitulate, this research demonstrates that seeds of different Vitis species, especially V. riparia and V. californica, are sources of molecules with antioxidant and antimicrobial activities that can be used in different sectors, such as in the food, cosmetic, and pharmaceutical industries. Full article
(This article belongs to the Special Issue Plant Bioactive Compounds: Extraction, Identification and Biological Activities)
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14 pages, 1913 KiB  
Review
The History of mARC
by Bernd Clement and Michel A. Struwe
Molecules 2023, 28(12), 4713; https://doi.org/10.3390/molecules28124713 - 12 Jun 2023
Cited by 17 | Viewed by 3490
Abstract
The mitochondrial amidoxime-reducing component (mARC) is the most recently discovered molybdoenzyme in humans after sulfite oxidase, xanthine oxidase and aldehyde oxidase. Here, the timeline of mARC’s discovery is briefly described. The story begins with investigations into N-oxidation of pharmaceutical drugs and model [...] Read more.
The mitochondrial amidoxime-reducing component (mARC) is the most recently discovered molybdoenzyme in humans after sulfite oxidase, xanthine oxidase and aldehyde oxidase. Here, the timeline of mARC’s discovery is briefly described. The story begins with investigations into N-oxidation of pharmaceutical drugs and model compounds. Many compounds are N-oxidized extensively in vitro, but it turned out that a previously unknown enzyme catalyzes the retroreduction of the N-oxygenated products in vivo. After many years, the molybdoenzyme mARC could finally be isolated and identified in 2006. mARC is an important drug-metabolizing enzyme and N-reduction by mARC has been exploited very successfully for prodrug strategies, that allow oral administration of otherwise poorly bioavailable therapeutic drugs. Recently, it was demonstrated that mARC is a key factor in lipid metabolism and likely involved in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). The exact link between mARC and lipid metabolism is not yet fully understood. Regardless, many now consider mARC a potential drug target for the prevention or treatment of liver diseases. This article focusses on discoveries related to mammalian mARC enzymes. mARC homologues have been studied in algae, plants and bacteria. These will not be discussed extensively here. Full article
(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)
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17 pages, 5263 KiB  
Article
Reflectance Spectroscopy as a Novel Tool for Thickness Measurements of Paint Layers
by Alice Dal Fovo, Marina Martínez-Weinbaum, Mohamed Oujja, Marta Castillejo and Raffaella Fontana
Molecules 2023, 28(12), 4683; https://doi.org/10.3390/molecules28124683 - 9 Jun 2023
Cited by 8 | Viewed by 2985
Abstract
A major challenge in heritage science is the non-invasive cross-sectional analysis of paintings. When low-energy probes are used, the presence of opaque media can significantly hinder the penetration of incident radiation, as well as the collection of the backscattered signal. Currently, no technique [...] Read more.
A major challenge in heritage science is the non-invasive cross-sectional analysis of paintings. When low-energy probes are used, the presence of opaque media can significantly hinder the penetration of incident radiation, as well as the collection of the backscattered signal. Currently, no technique is capable of uniquely and noninvasively measuring the micrometric thickness of heterogeneous materials, such as pictorial layers, for any painting material. The aim of this work was to explore the possibility of extracting stratigraphic information from reflectance spectra obtained by diffuse reflectance spectroscopy (DRS). We tested the proposed approach on single layers of ten pure acrylic paints. The chemical composition of each paint was first characterised by micro-Raman and laser-induced breakdown spectroscopies. The spectral behaviour was analysed by both Fibre Optics Reflectance Spectroscopy (FORS) and Vis-NIR multispectral reflectance imaging. We showed that there is a clear correlation between the spectral response of acrylic paint layers and their micrometric thickness, which was previously measured by Optical Coherence Tomography (OCT). Based on significant spectral features, exponential functions of reflectance vs. thickness were obtained for each paint, which can be used as calibration curves for thickness measurements. To the best of our knowledge, similar approaches for cross-sectional measurements of paint layers have never been tested. Full article
(This article belongs to the Special Issue Advances in Analytical Strategies to Study Cultural Heritage Samples)
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27 pages, 1646 KiB  
Review
The Role of Extracellular Matrix (ECM) Adhesion Motifs in Functionalised Hydrogels
by Anna J. Morwood, Ikhlas A. El-Karim, Susan A. Clarke and Fionnuala T. Lundy
Molecules 2023, 28(12), 4616; https://doi.org/10.3390/molecules28124616 - 7 Jun 2023
Cited by 28 | Viewed by 5195
Abstract
To create functional tissue engineering scaffolds, biomaterials should mimic the native extracellular matrix of the tissue to be regenerated. Simultaneously, the survival and functionality of stem cells should also be enhanced to promote tissue organisation and repair. Hydrogels, but in particular, peptide hydrogels, [...] Read more.
To create functional tissue engineering scaffolds, biomaterials should mimic the native extracellular matrix of the tissue to be regenerated. Simultaneously, the survival and functionality of stem cells should also be enhanced to promote tissue organisation and repair. Hydrogels, but in particular, peptide hydrogels, are an emerging class of biocompatible scaffolds which act as promising self-assembling biomaterials for tissue engineering and regenerative therapies, ranging from articular cartilage regeneration at joint defects, to regenerative spinal cord injury following trauma. To enhance hydrogel biocompatibility, it has become imperative to consider the native microenvironment of the site for regeneration, where the use of functionalised hydrogels with extracellular matrix adhesion motifs has become a novel, emerging theme. In this review, we will introduce hydrogels in the context of tissue engineering, provide insight into the complexity of the extracellular matrix, investigate specific adhesion motifs that have been used to generate functionalised hydrogels and outline their potential applications in a regenerative medicine setting. It is anticipated that by conducting this review, we will provide greater insight into functionalised hydrogels, which may help translate their use towards therapeutic roles. Full article
(This article belongs to the Special Issue Bioactive Material for Wound Healing, Tissue Engineering and Regenerative Medicine)
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18 pages, 4064 KiB  
Article
Methods to Detect Volatile Organic Compounds for Breath Biopsy Using Solid-Phase Microextraction and Gas Chromatography–Mass Spectrometry
by Eray Schulz, Mark Woollam, Paul Grocki, Michael D. Davis and Mangilal Agarwal
Molecules 2023, 28(11), 4533; https://doi.org/10.3390/molecules28114533 - 3 Jun 2023
Cited by 20 | Viewed by 4460
Abstract
Volatile organic compounds (VOCs) are byproducts from metabolic pathways that can be detected in exhaled breath and have been reported as biomarkers for different diseases. The gold standard for analysis is gas chromatography–mass spectrometry (GC–MS), which can be coupled with various sampling methods. [...] Read more.
Volatile organic compounds (VOCs) are byproducts from metabolic pathways that can be detected in exhaled breath and have been reported as biomarkers for different diseases. The gold standard for analysis is gas chromatography–mass spectrometry (GC–MS), which can be coupled with various sampling methods. The current study aims to develop and compare different methods for sampling and preconcentrating VOCs using solid-phase microextraction (SPME). An in-house sampling method, direct-breath SPME (DB–SPME), was developed to directly extract VOCs from breath using a SPME fiber. The method was optimized by exploring different SPME types, the overall exhalation volume, and breath fractionation. DB–SPME was quantitatively compared to two alternative methods involving the collection of breath in a Tedlar bag. In one method, VOCs were directly extracted from the Tedlar bag (Tedlar–SPME) and in the other, the VOCs were cryothermally transferred from the Tedlar bag to a headspace vial (cryotransfer). The methods were verified and quantitatively compared using breath samples (n = 15 for each method respectively) analyzed by GC–MS quadrupole time-of-flight (QTOF) for compounds including but not limited to acetone, isoprene, toluene, limonene, and pinene. The cryotransfer method was the most sensitive, demonstrating the strongest signal for the majority of the VOCs detected in the exhaled breath samples. However, VOCs with low molecular weights, including acetone and isoprene, were detected with the highest sensitivity using the Tedlar–SPME. On the other hand, the DB–SPME was less sensitive, although it was rapid and had the lowest background GC–MS signal. Overall, the three breath-sampling methods can detect a wide variety of VOCs in breath. The cryotransfer method may be optimal when collecting a large number of samples using Tedlar bags, as it allows the long-term storage of VOCs at low temperatures (−80 °C), while Tedlar–SPME may be more effective when targeting relatively small VOCs. The DB-SPME method may be the most efficient when more immediate analyses and results are required. Full article
(This article belongs to the Special Issue Recent Advances in Volatile Organic Compounds Analysis in Various Matrices II)
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15 pages, 345 KiB  
Article
Volatile Compounds and Biological Activity of the Essential Oil of Aloysia citrodora Paláu: Comparison of Hydrodistillation and Microwave-Assisted Hydrodistillation
by Rafael M. Sprea, Luís H. M. Fernandes, Tânia C. S. P. Pires, Ricardo C. Calhelha, Pedro João Rodrigues and Joana S. Amaral
Molecules 2023, 28(11), 4528; https://doi.org/10.3390/molecules28114528 - 2 Jun 2023
Cited by 14 | Viewed by 2839
Abstract
Aromatic plants are a remarkable source of natural products. Aloysia citrodora Paláu (Verbenaceae), commonly known as lemon verbena, is a relevant source of essential oils with potential applications due to its lemony scent and bioactive properties. Studies carried out on this species have [...] Read more.
Aromatic plants are a remarkable source of natural products. Aloysia citrodora Paláu (Verbenaceae), commonly known as lemon verbena, is a relevant source of essential oils with potential applications due to its lemony scent and bioactive properties. Studies carried out on this species have focused on the volatile composition of the essential oil obtained by Clevenger hydrodistillation (CHD), with little information available on alternative extraction methodologies or the biological properties of the oil. Therefore, this work aimed to compare the volatile composition, antioxidant activity, cytotoxicity, anti-inflammatory and antibacterial activities of the essential oil extracted by conventional hydrodistillation by Clevenger (CHD) and Microwave-Assisted Hydrodistillation (MAHD). Significant differences (p < 0.05) were observed for some compounds, including the two major ones, geranial (18.7–21.1%) and neral (15.3–16.2%). Better antioxidant activity was exhibited by the MAHD essential oil in DPPH radical scavenging and reducing power assays, while no differences were observed in the cellular antioxidant assay. The MADH essential oil also presented higher inhibition against four tumoral cell lines and exhibited lower cytotoxicity in non-tumoral cells as compared with Clevenger-extracted essential oil. In contrast, the latter showed higher anti-inflammatory activity. Both essential oils were able to inhibit the growth of eleven out of the fifteen bacterial strains tested. Full article
(This article belongs to the Special Issue Applications and Medicinal Properties of Terpenoids)
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24 pages, 11487 KiB  
Review
Towards the Application of Purely Inorganic Icosahedral Boron Clusters in Emerging Nanomedicine
by Francesc Teixidor, Rosario Núñez and Clara Viñas
Molecules 2023, 28(11), 4449; https://doi.org/10.3390/molecules28114449 - 30 May 2023
Cited by 19 | Viewed by 3676
Abstract
Traditionally, drugs were obtained by extraction from medicinal plants, but more recently also by organic synthesis. Today, medicinal chemistry continues to focus on organic compounds and the majority of commercially available drugs are organic molecules, which can incorporate nitrogen, oxygen, and halogens, as [...] Read more.
Traditionally, drugs were obtained by extraction from medicinal plants, but more recently also by organic synthesis. Today, medicinal chemistry continues to focus on organic compounds and the majority of commercially available drugs are organic molecules, which can incorporate nitrogen, oxygen, and halogens, as well as carbon and hydrogen. Aromatic organic compounds that play important roles in biochemistry find numerous applications ranging from drug delivery to nanotechnology or biomarkers. We achieved a major accomplishment by demonstrating experimentally/theoretically that boranes, carboranes, as well as metallabis(dicarbollides), exhibit global 3D aromaticity. Based on the stability–aromaticity relationship, as well as on the progress made in the synthesis of derivatized clusters, we have opened up new applications of boron icosahedral clusters as key components in the field of novel healthcare materials. In this brief review, we present the results obtained at the Laboratory of Inorganic Materials and Catalysis (LMI) of the Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) with icosahedral boron clusters. These 3D geometric shape clusters, the semi-metallic nature of boron and the presence of exo-cluster hydrogen atoms that can interact with biomolecules through non-covalent hydrogen and dihydrogen bonds, play a key role in endowing these compounds with unique properties in largely unexplored (bio)materials. 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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14 pages, 3600 KiB  
Article
A Simple Method for Synthesis of Chitosan Nanoparticles with Ionic Gelation and Homogenization
by Nicolas Van Bavel, Travis Issler, Liping Pang, Max Anikovskiy and Elmar J. Prenner
Molecules 2023, 28(11), 4328; https://doi.org/10.3390/molecules28114328 - 25 May 2023
Cited by 46 | Viewed by 15945
Abstract
Chitosan nanoparticles (CNPs) are known to have great utility in many fields (pharmaceutical, agricultural, food industry, wastewater treatment, etc.). In this study we aimed to synthesize sub-100 nm CNPs as a precursor of new biopolymer-based virus surrogates for water applications. We present a [...] Read more.
Chitosan nanoparticles (CNPs) are known to have great utility in many fields (pharmaceutical, agricultural, food industry, wastewater treatment, etc.). In this study we aimed to synthesize sub-100 nm CNPs as a precursor of new biopolymer-based virus surrogates for water applications. We present a simple yet efficient synthesis procedure for obtaining high yield, monodisperse CNPs with size 68–77 nm. The CNPs were synthesized by ionic gelation using low molecular weight chitosan (deacetylation 75–85%) and tripolyphosphate as crosslinker, under rigorous homogenization to decrease size and increase uniformity, and purified by passing through 0.1 μm polyethersulfone syringe filters. The CNPs were characterized using dynamic light scattering, tunable resistive pulse sensing, and scanning electron microscopy. We demonstrate reproducibility of this method at two separate facilities. The effects of pH, ionic strength and three different purification methods on the size and polydispersity of CNP formation were examined. Larger CNPs (95–219) were produced under ionic strength and pH controls, and when purified using ultracentrifugation or size exclusion chromatography. Smaller CNPs (68–77 nm) were formulated using homogenization and filtration, and could readily interact with negatively charge proteins and DNA, making them an ideal precursor for the development of DNA-labelled, protein-coated virus surrogates for environmental water applications. Full article
(This article belongs to the Special Issue Chitosan, Chitosan Derivatives and Their Applications)
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21 pages, 837 KiB  
Review
Valorization of Fibrous Plant-Based Food Waste as Biosorbents for Remediation of Heavy Metals from Wastewater—A Review
by Ahasanul Karim, Zarifeh Raji, Antoine Karam and Seddik Khalloufi
Molecules 2023, 28(10), 4205; https://doi.org/10.3390/molecules28104205 - 20 May 2023
Cited by 28 | Viewed by 3801
Abstract
Mobilization of heavy metals in the environment has been a matter of concern for several decades due to their toxicity for humans, environments, and other living organisms. In recent years, use of inexpensive and abundantly available biosorbents generated from fibrous plant-based food-waste materials [...] Read more.
Mobilization of heavy metals in the environment has been a matter of concern for several decades due to their toxicity for humans, environments, and other living organisms. In recent years, use of inexpensive and abundantly available biosorbents generated from fibrous plant-based food-waste materials to remove heavy metals has garnered considerable research attention. The aim of this review is to investigate the applicability of using fibrous plant-based food waste, which comprises different components such as pectin, hemicellulose, cellulose, and lignin, to remove heavy metals from wastewater. This contribution confirms that plant-fiber-based food waste has the potential to bind heavy metals from wastewater and aqueous solutions. The binding capacities of these biosorbents vary depending on the source, chemical structure, type of metal, modification technology applied, and process conditions used to improve functionalities. This review concludes with a discussion of arguments and prospects, as well as future research directions, to support valorization of fibrous plant-based food waste as an efficient and promising strategy for water purification. Full article
(This article belongs to the Special Issue Polysaccharide-Based Biopolymer: Recent Development and Applications)
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19 pages, 2958 KiB  
Article
Comparative Study on Assisted Solvent Extraction Techniques for the Extraction of Biologically Active Compounds from Sideritis raeseri and Sideritis scardica
by Marika Mróz, Edyta Malinowska-Pańczyk, Agnieszka Bartoszek and Barbara Kusznierewicz
Molecules 2023, 28(10), 4207; https://doi.org/10.3390/molecules28104207 - 20 May 2023
Cited by 14 | Viewed by 3081
Abstract
The plants in the Sideritis genus are postulated to exhibit several important medicinal properties due to their unique chemical composition. To isolate the targeted phytochemical compounds, the selection of a suitable extraction method is of primary importance. In this work, a comparative study [...] Read more.
The plants in the Sideritis genus are postulated to exhibit several important medicinal properties due to their unique chemical composition. To isolate the targeted phytochemical compounds, the selection of a suitable extraction method is of primary importance. In this work, a comparative study on the phytochemical profiles of various Sideritis raeseri and Sideritis scardica extracts has been carried out. An untargeted metabolomics approach based on ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry was applied to investigate the metabolic differences between extracts obtained by conventional extraction and extractions assisted by microwaves, ultrasounds and high pressure. Additionally, the influence of extraction solvents on HPLC antioxidant profiles obtained following the derivatization of analytes with ABTS reagent was evaluated. A total of 102 metabolites have been putatively identified. The major secondary metabolites groups were classified as flavonoids, terpenoids, phenylethanoid glycosides and phenolic acids. The main antioxidants in the extracts were isoscutellarein and hypolaetin derivatives as well as verbascoside and chlorogenic acid. The results showed that 70% ethanol was the most effective extractant for different classes of phytochemicals including antioxidants. In addition, extraction supported with microwaves, ultrasounds or high pressure improved the overall recovery of metabolites by about 3 times compared to the conventional extraction method. Full article
(This article belongs to the Special Issue Extraction and Application of Nutrients and Functional Compounds from Food)
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21 pages, 7193 KiB  
Article
Adsorption of Brilliant Green Dye onto a Mercerized Biosorbent: Kinetic, Thermodynamic, and Molecular Docking Studies
by Andra-Cristina Enache, Corneliu Cojocaru, Petrisor Samoila, Victor Ciornea, Roxana Apolzan, Georgeta Predeanu and Valeria Harabagiu
Molecules 2023, 28(10), 4129; https://doi.org/10.3390/molecules28104129 - 16 May 2023
Cited by 29 | Viewed by 3695
Abstract
This study reports the valorization of pistachio shell agricultural waste, aiming to develop an eco-friendly and cost-effective biosorbent for cationic brilliant green (BG) dye adsorption from aqueous media. Pistachio shells were mercerized in an alkaline environment, resulting in the treated adsorbent (PSNaOH [...] Read more.
This study reports the valorization of pistachio shell agricultural waste, aiming to develop an eco-friendly and cost-effective biosorbent for cationic brilliant green (BG) dye adsorption from aqueous media. Pistachio shells were mercerized in an alkaline environment, resulting in the treated adsorbent (PSNaOH). The morphological and structural features of the adsorbent were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy, and polarized light microscopy. The pseudo-first-order (PFO) kinetic model best described the adsorption kinetics of the BG cationic dye onto PSNaOH biosorbents. In turn, the equilibrium data were best fitted to the Sips isotherm model. The maximum adsorption capacity decreased with temperature (from 52.42 mg/g at 300 K to 46.42 mg/g at 330 K). The isotherm parameters indicated improved affinity between the biosorbent surface and BG molecules at lower temperatures (300 K). The thermodynamic parameters estimated on the basis of the two approaches indicated a spontaneous (ΔG < 0) and exothermic (ΔH < 0) adsorption process. The design of experiments (DoE) and the response surface methodology (RSM) were employed to establish optimal conditions (sorbent dose (SD) = 4.0 g/L and initial concentration (C0) = 10.1 mg/L), yielding removal efficiency of 98.78%. Molecular docking simulations were performed to disclose the intermolecular interactions between the BG dye and lignocellulose-based adsorbent. Full article
(This article belongs to the Special Issue Exclusive Feature Papers in Physical Chemistry)
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17 pages, 3935 KiB  
Article
Molecular Basis for the Selectivity of DHA and EPA in Sudlow’s Drug Binding Sites in Human Serum Albumin with the Combined Use of NMR and Docking Calculations
by Eleni Alexandri, Themistoklis Venianakis, Alexandra Primikyri, Georgios Papamokos and Ioannis P. Gerothanassis
Molecules 2023, 28(9), 3724; https://doi.org/10.3390/molecules28093724 - 26 Apr 2023
Cited by 18 | Viewed by 4740
Abstract
Medium- and long-chain saturated and unsaturated free fatty acids (FFAs) are known to bind to human serum albumin (HSA), the main plasma carrier protein. Atomic-level structural data regarding the binding mode in Sudlow’s sites I (FA7) and II (FA4, FA3) of the polyunsaturated [...] Read more.
Medium- and long-chain saturated and unsaturated free fatty acids (FFAs) are known to bind to human serum albumin (HSA), the main plasma carrier protein. Atomic-level structural data regarding the binding mode in Sudlow’s sites I (FA7) and II (FA4, FA3) of the polyunsaturated ω-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), however, are largely unknown. Herein, we report the combined use of saturation transfer difference (STD) and Interligand NOEs for Pharmacophore Mapping (INPHARMA) NMR techniques and molecular docking calculations to investigate the binding mode of DHA and EPA in Sudlow’s sites Ι and ΙΙ of HSA. The docking calculations and the significant number of interligand NOEs between DHA and EPA and the drugs warfarin and ibuprofen, which are stereotypical ligands for Sudlow’s sites I and II, respectively, were interpreted in terms of competitive binding modes and the presence of two orientations of DHA and EPA at the binding sites FA7 and FA4. The exceptional flexibility of the long-chain DHA and EPA and the formation of strongly folded structural motives are the key properties of HSA–PUFA complexes. Full article
(This article belongs to the Special Issue New Insights into Nuclear Magnetic Resonance (NMR) Spectroscopy)
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42 pages, 1940 KiB  
Review
Combination Chemotherapy with Selected Polyphenols in Preclinical and Clinical Studies—An Update Overview
by Cvijeta Jakobušić Brala, Ana Karković Marković, Azra Kugić, Jelena Torić and Monika Barbarić
Molecules 2023, 28(9), 3746; https://doi.org/10.3390/molecules28093746 - 26 Apr 2023
Cited by 32 | Viewed by 6086
Abstract
This review article describes studies published over the past five years on the combination of polyphenols, which are the most studied in the field of anticancer effects (curcumin, quercetin, resveratrol, epigallocatechin gallate, and apigenin) and chemotherapeutics such as cisplatin, 5-fluorouracil, oxaliplatin, paclitaxel, etc. [...] Read more.
This review article describes studies published over the past five years on the combination of polyphenols, which are the most studied in the field of anticancer effects (curcumin, quercetin, resveratrol, epigallocatechin gallate, and apigenin) and chemotherapeutics such as cisplatin, 5-fluorouracil, oxaliplatin, paclitaxel, etc. According to WHO data, research has been limited to five cancers with the highest morbidity rate (lung, colorectal, liver, gastric, and breast cancer). A systematic review of articles published in the past five years (from January 2018 to January 2023) was carried out with the help of all Web of Science databases and the available base of clinical studies. Based on the preclinical studies presented in this review, polyphenols can enhance drug efficacy and reduce chemoresistance through different molecular mechanisms. Considering the large number of studies, curcumin could be a molecule in future chemotherapy cocktails. One of the main problems in clinical research is related to the limited bioavailability of most polyphenols. The design of a new co-delivery system for drugs and polyphenols is essential for future clinical research. Some polyphenols work in synergy with chemotherapeutic drugs, but some polyphenols can act antagonistically, so caution is always required. Full article
(This article belongs to the Special Issue Biological Activity of Natural Compounds in Combination with Drugs)
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16 pages, 1498 KiB  
Review
The Buzz on Insecticides: A Review of Uses, Molecular Structures, Targets, Adverse Effects, and Alternatives
by Maria F. Araújo, Elisabete M. S. Castanheira and Sérgio F. Sousa
Molecules 2023, 28(8), 3641; https://doi.org/10.3390/molecules28083641 - 21 Apr 2023
Cited by 82 | Viewed by 17247
Abstract
Insecticides play a critical role in controlling the spread of insect-borne diseases and preserving crop health. These chemical substances are specifically formulated to kill or manage insect populations. Over the years, various types of insecticides have been developed, including organophosphates, carbamates, pyrethroids, and [...] Read more.
Insecticides play a critical role in controlling the spread of insect-borne diseases and preserving crop health. These chemical substances are specifically formulated to kill or manage insect populations. Over the years, various types of insecticides have been developed, including organophosphates, carbamates, pyrethroids, and neonicotinoids, each with unique modes of action, physiological targets, and efficacy. Despite the advantages that insecticides offer, it is imperative to recognize the potential consequences on non-target species, the environment, and human health. It is therefore crucial to follow recommended label instructions and employ integrated pest management practices for the judicious use of insecticides. This review article provides an in-depth examination of the various types of insecticides, including their modes of action, physiological targets, environmental and human health impacts, and alternatives. The aim is to furnish a comprehensive overview of insecticides and to emphasize the significance of responsible and sustainable utilization. Full article
(This article belongs to the Special Issue Novel Targets in Pest Control: Molecular Characterization, Structural and Biochemical Properties, Physiological Functions, and Evolution)
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19 pages, 1660 KiB  
Article
Bioactive Compounds and Antioxidant Composition of Nut Bars with Addition of Various Edible Insect Flours
by Dorota Gumul, Joanna Oracz, Stanisław Kowalski, Anna Mikulec, Magdalena Skotnicka, Kaja Karwowska and Anna Areczuk
Molecules 2023, 28(8), 3556; https://doi.org/10.3390/molecules28083556 - 18 Apr 2023
Cited by 19 | Viewed by 3077
Abstract
Edible insects represent a new functional source of nutrients that can contribute to solving nutritional deficiency problems. The antioxidant potential and bioactive compounds of nut bars with the addition of three edible insects were evaluated. Acheta domesticus L., Alphitobius diaperinus P. and Tenebrio [...] Read more.
Edible insects represent a new functional source of nutrients that can contribute to solving nutritional deficiency problems. The antioxidant potential and bioactive compounds of nut bars with the addition of three edible insects were evaluated. Acheta domesticus L., Alphitobius diaperinus P. and Tenebrio molitor L. flours were used. A 30% share of insect flour in the bars resulted in significantly greater antioxidant activity (TPC increased from 190.19 for standard bars to 309.45 mg catechin/100 g for bars with 30% addition of cricket flour). Insect flour contributed significantly to an increase in 2,5-dihydrobenzoic acid (from 0.12 for bars with a 15% share of buffalo worm flour to 0.44 mg/100 g in the case of bars with a 30% share of cricket flour) and chlorogenic acid in all bars (from 0.58 for bars with a 15% share of cricket flour to 3.28 mg/100 g for bars with a 30% addition of buffalo worm flour), compared to the standard. The highest content of tocopherols was found in bars with cricket flour, compared to standard bars (43.57 and 24.06 mg/100 g of fat, respectively). The dominant sterol in bars enriched with insect powder was cholesterol. The highest amount of it was found in cricket bars, and the lowest in mealworm bars (64.16 and 21.62 mg/100 g of fat, respectively). The enrichment of nut bars with insect flours raises the levels of valuable phytosterols in the final product. The addition of edible insect flours reduced the perception of most sensory attributes of the bars, compared to the standard bar. Full article
(This article belongs to the Special Issue Functional Foods: Bioactive Compounds, Antioxidants and Anti-inflammatory Activities)
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20 pages, 4552 KiB  
Article
An Expedited Route to Optical and Electronic Properties at Finite Temperature via Unsupervised Learning
by Fulvio Perrella, Federico Coppola, Nadia Rega and Alessio Petrone
Molecules 2023, 28(8), 3411; https://doi.org/10.3390/molecules28083411 - 12 Apr 2023
Cited by 17 | Viewed by 2146
Abstract
Electronic properties and absorption spectra are the grounds to investigate molecular electronic states and their interactions with the environment. Modeling and computations are required for the molecular understanding and design strategies of photo-active materials and sensors. However, the interpretation of such properties demands [...] Read more.
Electronic properties and absorption spectra are the grounds to investigate molecular electronic states and their interactions with the environment. Modeling and computations are required for the molecular understanding and design strategies of photo-active materials and sensors. However, the interpretation of such properties demands expensive computations and dealing with the interplay of electronic excited states with the conformational freedom of the chromophores in complex matrices (i.e., solvents, biomolecules, crystals) at finite temperature. Computational protocols combining time dependent density functional theory and ab initio molecular dynamics (MD) have become very powerful in this field, although they require still a large number of computations for a detailed reproduction of electronic properties, such as band shapes. Besides the ongoing research in more traditional computational chemistry fields, data analysis and machine learning methods have been increasingly employed as complementary approaches for efficient data exploration, prediction and model development, starting from the data resulting from MD simulations and electronic structure calculations. In this work, dataset reduction capabilities by unsupervised clustering techniques applied to MD trajectories are proposed and tested for the ab initio modeling of electronic absorption spectra of two challenging case studies: a non-covalent charge-transfer dimer and a ruthenium complex in solution at room temperature. The K-medoids clustering technique is applied and is proven to be able to reduce by ∼100 times the total cost of excited state calculations on an MD sampling with no loss in the accuracy and it also provides an easier understanding of the representative structures (medoids) to be analyzed on the molecular scale. Full article
(This article belongs to the Special Issue Exclusive Feature Papers in Physical Chemistry)
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36 pages, 1985 KiB  
Review
Flavour Volatiles of Fermented Vegetable and Fruit Substrates: A Review
by Sarathadevi Rajendran, Patrick Silcock and Phil Bremer
Molecules 2023, 28(7), 3236; https://doi.org/10.3390/molecules28073236 - 4 Apr 2023
Cited by 46 | Viewed by 4991
Abstract
Health, environmental and ethical concerns have resulted in a dramatic increase in demand for plant-based dairy analogues. While the volatile organic compounds (VOCs) responsible for the characteristic flavours of dairy-based products have been extensively studied, little is known about how to reproduce such [...] Read more.
Health, environmental and ethical concerns have resulted in a dramatic increase in demand for plant-based dairy analogues. While the volatile organic compounds (VOCs) responsible for the characteristic flavours of dairy-based products have been extensively studied, little is known about how to reproduce such flavours using only plant-based substrates. As a first step in their development, this review provides an overview of the VOCs associated with fermented (bacteria and/or fungi/yeast) vegetable and fruit substrates. Following PRISMA guidelines and using two English databases (Web of Science and Scopus), thirty-five suitable research papers were identified. The number of fermentation-derived VOCs detected ranged from 32 to 118 (across 30 papers), while 5 papers detected fewer (10 to 25). Bacteria, including lactic acid bacteria (LAB), fungi, and yeast were the micro-organisms used, with LAB being the most commonly reported. Ten studies used a single species, 21 studies used a single type (bacteria, fungi or yeast) of micro-organisms and four studies used mixed fermentation. The nature of the fermentation-derived VOCs detected (alcohols, aldehydes, esters, ketones, acids, terpenes and norisoprenoids, phenols, furans, sulphur compounds, alkenes, alkanes, and benzene derivatives) was dependent on the composition of the vegetable/fruit matrix, the micro-organisms involved, and the fermentation conditions. Full article
(This article belongs to the Special Issue Flavour Compounds of Fruit and Fruit Products)
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10 pages, 2208 KiB  
Article
Sulphur- and Selenium-for-Oxygen Replacement as a Strategy to Obtain Dual Type I/Type II Photosensitizers for Photodynamic Therapy
by Mario Prejanò, Marta Erminia Alberto, Bruna Clara De Simone, Tiziana Marino, Marirosa Toscano and Nino Russo
Molecules 2023, 28(7), 3153; https://doi.org/10.3390/molecules28073153 - 1 Apr 2023
Cited by 13 | Viewed by 2680
Abstract
The effect on the photophysical properties of sulfur- and selenium-for-oxygen replacement in the skeleton of the oxo-4-dimethylaminonaphthalimide molecule (DMNP) has been explored at the density functional (DFT) level of theory. Structural parameters, excitation energies, singlet–triplet energy gaps (ΔES-T), and spin–orbit coupling [...] Read more.
The effect on the photophysical properties of sulfur- and selenium-for-oxygen replacement in the skeleton of the oxo-4-dimethylaminonaphthalimide molecule (DMNP) has been explored at the density functional (DFT) level of theory. Structural parameters, excitation energies, singlet–triplet energy gaps (ΔES-T), and spin–orbit coupling constants (SOC) have been computed. The determined SOCs indicate an enhanced probability of intersystem crossing (ISC) in both the thio- and seleno-derivatives (SDMNP and SeDMNP, respectively) and, consequently, an enhancement of the singlet oxygen quantum yields. Inspection of Type I reactions reveals that the electron transfer mechanisms leading to the generation of superoxide is feasible for all the compounds, suggesting a dual Type I/Type II activity. Full article
(This article belongs to the Special Issue Advances in Computational and Theoretical Chemistry)
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55 pages, 10330 KiB  
Review
Ion-Imprinted Polymeric Materials for Selective Adsorption of Heavy Metal Ions from Aqueous Solution
by Maria Marinela Lazar, Claudiu-Augustin Ghiorghita, Ecaterina Stela Dragan, Doina Humelnicu and Maria Valentina Dinu
Molecules 2023, 28(6), 2798; https://doi.org/10.3390/molecules28062798 - 20 Mar 2023
Cited by 40 | Viewed by 6866
Abstract
The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle [...] Read more.
The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle of molecular imprinting methodology, have emerged as an innovative solution. Recent advances in IIPs have shown that they exhibit higher selectivity coefficients than non-imprinted ones, which could support a large range of environmental applications starting from extraction and monitoring of HMIs to their detection and quantification. This review will emphasize the application of IIPs for selective removal of transition metal ions (including HMIs, precious metal ions, radionuclides, and rare earth metal ions) from aqueous solution by critically analyzing the most relevant literature studies from the last decade. In the first part of this review, the chemical components of IIPs, the main ion-imprinting technologies as well as the characterization methods used to evaluate the binding properties are briefly presented. In the second part, synthesis parameters, adsorption performance, and a descriptive analysis of solid phase extraction of heavy metal ions by various IIPs are provided. Full article
(This article belongs to the Special Issue Exclusive Review Papers in Green Chemistry)
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15 pages, 22343 KiB  
Article
Grape Pomace as a Natural Source of Phenolic Compounds: Solvent Screening and Extraction Optimization
by Rafaela P. Rodrigues, Ana M. Sousa, Licínio M. Gando-Ferreira and Margarida J. Quina
Molecules 2023, 28(6), 2715; https://doi.org/10.3390/molecules28062715 - 17 Mar 2023
Cited by 38 | Viewed by 4513
Abstract
The optimization of extraction by using solvents of phenolic compounds (TPh) of grape pomace (GP) based on a central composite design was investigated. The GP was characterized, and preliminary assays were conducted with five different solvents (water, ethanol, acetone, methanol, and butanol) and [...] Read more.
The optimization of extraction by using solvents of phenolic compounds (TPh) of grape pomace (GP) based on a central composite design was investigated. The GP was characterized, and preliminary assays were conducted with five different solvents (water, ethanol, acetone, methanol, and butanol) and the aqueous mixtures thereof. Ethanol and acetone were revealed to be the best solvents for TPh extraction. The main extraction parameters (temperature—T, time—t, solvent concentration, and liquid–solid ratio—L/S) were optimized by using a central composite design. The optimized conditions for the ethanol extraction (T = 60 °C, t = 1.5 h, L/S = 25 mL/gdryGP) and for acetone (T = 50 °C, t = 1.5 h, L/S = 25 mL/gdryGP) were determined. Single-stage extraction revealed a TPh of 45.18 ± 9.51 mgGAE/gdryGP for acetone and a TPh of 38.70 ± 3.64 mgGAE/gdryGP for ethanol. The characterization of the extracts revealed the presence of gallic acid, caffeic acid, syringic acid, vanillic acid, chlorogenic acid, and p-coumaric acid, where the concentration of the first three compounds stands out in all extracts. A three-stage extraction increased the yield of ethanol to 63.3 mg GAE/gdryGP and the yield of acetone to 59.2 mg GAE/gdryGP. Overall, both solvents allow the extraction of phenolic compounds of grape pomace, but ethanol is commonly considered a greener solvent for this purpose. Full article
(This article belongs to the Collection Recycling of Biomass Resources: Biofuels and Biochemicals)
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29 pages, 4566 KiB  
Review
Recent Developments in Sonochemical Synthesis of Nanoporous Materials
by Sylwia Głowniak, Barbara Szczęśniak, Jerzy Choma and Mietek Jaroniec
Molecules 2023, 28(6), 2639; https://doi.org/10.3390/molecules28062639 - 14 Mar 2023
Cited by 71 | Viewed by 9219
Abstract
Ultrasounds are commonly used in medical imaging, solution homogenization, navigation, and ranging, but they are also a great energy source for chemical reactions. Sonochemistry uses ultrasounds and thus realizes one of the basic concepts of green chemistry, i.e., energy savings. Moreover, reduced reaction [...] Read more.
Ultrasounds are commonly used in medical imaging, solution homogenization, navigation, and ranging, but they are also a great energy source for chemical reactions. Sonochemistry uses ultrasounds and thus realizes one of the basic concepts of green chemistry, i.e., energy savings. Moreover, reduced reaction time, mostly using water as a solvent, and better product yields are among the many factors that make ultrasound-induced reactions greener than those performed under conventional conditions. Sonochemistry has been successfully implemented for the preparation of various materials; this review covers sonochemically synthesized nanoporous materials. For instance, sonochemical-assisted methods afforded ordered mesoporous silicas, spherical mesoporous silicas, periodic mesoporous organosilicas, various metal oxides, biomass-derived activated carbons, carbon nanotubes, diverse metal-organic frameworks, and covalent organic frameworks. Among these materials, highly porous samples have also been prepared, such as garlic peel-derived activated carbon with an apparent specific surface area of 3887 m2/g and MOF-177 with an SSA of 4898 m2/g. Additionally, many of them have been examined for practical usage in gas adsorption, water treatment, catalysis, and energy storage-related applications, yielding satisfactory results. Full article
(This article belongs to the Special Issue Advances in Ultrasound Chemistry)
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21 pages, 7677 KiB  
Article
Ultrasound-Assisted Extraction of Blackberry Seed Oil: Optimization and Oil Characterization
by Petronela L. Matei, Iuliana Deleanu, Ana M. Brezoiu, Nicoleta A. Chira, Cristina Busuioc, Gabriela Isopencu, Mihaela Cîlțea-Udrescu, Elvira Alexandrescu and Anicuta Stoica-Guzun
Molecules 2023, 28(6), 2486; https://doi.org/10.3390/molecules28062486 - 8 Mar 2023
Cited by 19 | Viewed by 3430
Abstract
Ultrasound-assisted extraction (UAE) was applied to extract oil from blackberry (BB) seeds. The effect of UAE conditions on oil recovery and quality was investigated. Favorable experimental conditions (ultrasound intensity (UI), extraction temperature, and time) were investigated using response surface methodology (RSM). A Box–Behnken [...] Read more.
Ultrasound-assisted extraction (UAE) was applied to extract oil from blackberry (BB) seeds. The effect of UAE conditions on oil recovery and quality was investigated. Favorable experimental conditions (ultrasound intensity (UI), extraction temperature, and time) were investigated using response surface methodology (RSM). A Box–Behnken design was used to predict optimized conditions for BB seed oil extraction. These conditions were as follows: 13.77 W/cm2 UI, 45 °C extraction temperature, and 15 min extraction time. The experimental value obtained for extraction efficiency under optimal conditions was 87 ± 0.34%, in good agreement with the optimized predicted value. UAE does not affect the oil composition and confers higher antioxidant values in BB seed oil in comparison with Soxhlet extraction. Full article
(This article belongs to the Special Issue Advances in Ultrasound Chemistry)
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30 pages, 6308 KiB  
Review
Molecular Pathways for Polymer Degradation during Conventional Processing, Additive Manufacturing, and Mechanical Recycling
by Daniel V. A. Ceretti, Mariya Edeleva, Ludwig Cardon and Dagmar R. D’hooge
Molecules 2023, 28(5), 2344; https://doi.org/10.3390/molecules28052344 - 3 Mar 2023
Cited by 55 | Viewed by 8301
Abstract
The assessment of the extent of degradation of polymer molecules during processing via conventional (e.g., extrusion and injection molding) and emerging (e.g., additive manufacturing; AM) techniques is important for both the final polymer material performance with respect to technical specifications and the material [...] Read more.
The assessment of the extent of degradation of polymer molecules during processing via conventional (e.g., extrusion and injection molding) and emerging (e.g., additive manufacturing; AM) techniques is important for both the final polymer material performance with respect to technical specifications and the material circularity. In this contribution, the most relevant (thermal, thermo-mechanical, thermal-oxidative, hydrolysis) degradation mechanisms of polymer materials during processing are discussed, addressing conventional extrusion-based manufacturing, including mechanical recycling, and AM. An overview is given of the most important experimental characterization techniques, and it is explained how these can be connected with modeling tools. Case studies are incorporated, dealing with polyesters, styrene-based materials, and polyolefins, as well as the typical AM polymers. Guidelines are formulated in view of a better molecular scale driven degradation control. Full article
(This article belongs to the Section Materials Chemistry)
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17 pages, 682 KiB  
Review
A Review on the Effect of Calcium Sequestering Salts on Casein Micelles: From Model Milk Protein Systems to Processed Cheese
by Gaurav Kr Deshwal, Laura G. Gómez-Mascaraque, Mark Fenelon and Thom Huppertz
Molecules 2023, 28(5), 2085; https://doi.org/10.3390/molecules28052085 - 23 Feb 2023
Cited by 31 | Viewed by 7239
Abstract
Phosphates and citrates are calcium sequestering salts (CSS) most commonly used in the manufacture of processed cheese, either singly or in mixtures. Caseins are the main structure forming elements in processed cheese. Calcium sequestering salts decrease the concentration of free calcium ions by [...] Read more.
Phosphates and citrates are calcium sequestering salts (CSS) most commonly used in the manufacture of processed cheese, either singly or in mixtures. Caseins are the main structure forming elements in processed cheese. Calcium sequestering salts decrease the concentration of free calcium ions by sequestering calcium from the aqueous phase and dissociates the casein micelles into small clusters by altering the calcium equilibrium, thereby resulting in enhanced hydration and voluminosity of the micelles. Several researchers have studied milk protein systems such as rennet casein, milk protein concentrate, skim milk powder, and micellar casein concentrate to elucidate the influence of calcium sequestering salts on (para-)casein micelles. This review paper provides an overview of the effects of calcium sequestering salts on the properties of casein micelles and consequently the physico-chemical, textural, functional, and sensorial attributes of processed cheese. A lack of proper understanding of the mechanisms underlying the action of calcium sequestering salts on the processed cheese characteristics increases the risk of failed production, leading to the waste of resources and unacceptable sensorial, appearance, and textural attributes, which adversely affect the financial side of processors and customer expectations. Full article
(This article belongs to the Special Issue Featured Review Papers in Food Chemistry)
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13 pages, 2384 KiB  
Article
Acenocoumarol Exerts Anti-Inflammatory Activity via the Suppression of NF-κB and MAPK Pathways in RAW 264.7 Cells
by Hyun-Ju Han and Chang-Gu Hyun
Molecules 2023, 28(5), 2075; https://doi.org/10.3390/molecules28052075 - 22 Feb 2023
Cited by 20 | Viewed by 3245
Abstract
The repurposing of already-approved drugs has emerged as an alternative strategy to rapidly identify effective, safe, and conveniently available new therapeutic indications against human diseases. The current study aimed to assess the repurposing of the anticoagulant drug acenocoumarol for the treatment of chronic [...] Read more.
The repurposing of already-approved drugs has emerged as an alternative strategy to rapidly identify effective, safe, and conveniently available new therapeutic indications against human diseases. The current study aimed to assess the repurposing of the anticoagulant drug acenocoumarol for the treatment of chronic inflammatory diseases (e.g., atopic dermatitis and psoriasis) and investigate the potential underlying mechanisms. For this purpose, we used murine macrophage RAW 264.7 as a model in experiments aimed at investigating the anti-inflammatory effects of acenocoumarol in inhibiting the production of pro-inflammatory mediators and cytokines. We demonstrate that acenocoumarol significantly decreases nitric oxide (NO), prostaglandin (PG)E2, tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β levels in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Acenocoumarol also inhibits the expression of NO synthase (iNOS) and cyclooxygenase (COX)-2, potentially explaining the acenocoumarol-induced decrease in NO and PGE2 production. In addition, acenocoumarol inhibits the phosphorylation of mitogen-activated protein kinases (MAPKs), c-Jun N terminal kinase (JNK), p38 MAPK, and extracellular signal-regulated kinase (ERK), in addition to decreasing the subsequent nuclear translocation of nuclear factor κB (NF-κB). This indicates that acenocoumarol attenuates the macrophage secretion of TNF-α, IL-6, IL-1β, and NO, inducing iNOS and COX-2 expression via the inhibition of the NF-κB and MAPK signaling pathways. In conclusion, our results demonstrate that acenocoumarol can effectively attenuate the activation of macrophages, suggesting that acenocoumarol is a potential candidate for drug repurposing as an anti-inflammatory agent. Full article
(This article belongs to the Special Issue Bioactive Molecules Targeting Inflammation Processes in Related Diseases)
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26 pages, 4261 KiB  
Article
The (Poly)phenolic Profile of Separate Winery By-Products Reveals Potential Antioxidant Synergies
by Antonio Costa-Pérez, Sonia Medina, Paola Sánchez-Bravo, Raúl Domínguez-Perles and Cristina García-Viguera
Molecules 2023, 28(5), 2081; https://doi.org/10.3390/molecules28052081 - 22 Feb 2023
Cited by 25 | Viewed by 3309
Abstract
The by-products of grapes (Vitis vinifera L.) in the winemaking process present a diverse phytochemical profile of (poly)phenols, essentially represented by phenolic acids, flavonoids, and stilbenes, which have health benefits. In winemaking, solid (grape stems and pomace) and semisolid (wine lees) by-products [...] Read more.
The by-products of grapes (Vitis vinifera L.) in the winemaking process present a diverse phytochemical profile of (poly)phenols, essentially represented by phenolic acids, flavonoids, and stilbenes, which have health benefits. In winemaking, solid (grape stems and pomace) and semisolid (wine lees) by-products are generated, negatively impacting the sustainability of the agro-food activity and the local environment. Although information on the phytochemical profile of grape stems and pomace has been reported, especially information concerning (poly)phenols, research on wine lees is necessary to take advantage of the compositional traits of this residue. So, in the present work, an updated, in-depth comparison of the (poly)phenolic profiles of these three resulting matrices in the agro-food industry has been carried out to provide new knowledge and interesting data on the action of yeast and lactic acid bacteria (LAB) metabolism in the diversification of phenolic composition; additionally, we extract complementarities for the possible joint application of the three residues. The phytochemical analysis of the extracts was carried out using HPLC-PDA-ESI-MSn. The (poly)phenolic profiles of the residues showed significant discrepancies. The results obtained showed that the greatest diversity of (poly)phenols was found in the stems of the grapes, followed closely by the lees. Through technological insights, it has been suggested that yeasts and LAB, responsible for the fermentation of must, might play a key role in the transformation of phenolic compounds. This would provide new molecules with specific bioavailability and bioactivity features, which might interact with different molecular targets and, consequently, improve the biological potential of these underexploited residues. Full article
(This article belongs to the Special Issue Phytochemical and Antioxidant Analysis of Medicinal and Food Plants Towards Bioactive Food and Pharmaceutical Resources)
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28 pages, 13216 KiB  
Review
p-Xylene Oxidation to Terephthalic Acid: New Trends
by Hugo M. Lapa and Luísa M. D. R. S. Martins
Molecules 2023, 28(4), 1922; https://doi.org/10.3390/molecules28041922 - 17 Feb 2023
Cited by 22 | Viewed by 9460
Abstract
Large-scale terephthalic acid production from the oxidation of p-xylene is an especially important process in the polyester industry, as it is mainly used in polyethylene terephthalate (PET) manufacturing, a polymer that is widely used in fibers, films, and plastic products. This review [...] Read more.
Large-scale terephthalic acid production from the oxidation of p-xylene is an especially important process in the polyester industry, as it is mainly used in polyethylene terephthalate (PET) manufacturing, a polymer that is widely used in fibers, films, and plastic products. This review presents and discusses catalytic advances and new trends in terephthalic acid production (since 2014), innovations in terephthalic acid purification processes, and simulations of reactors and reaction mechanisms. Full article
(This article belongs to the Special Issue Feature Papers in Applied Chemistry)
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23 pages, 6784 KiB  
Article
Characteristics of Hybrid Bioglass-Chitosan Coatings on the Plasma Activated PEEK Polymer
by Kacper Przykaza, Małgorzata Jurak, Grzegorz Kalisz, Robert Mroczka and Agnieszka Ewa Wiącek
Molecules 2023, 28(4), 1729; https://doi.org/10.3390/molecules28041729 - 11 Feb 2023
Cited by 15 | Viewed by 3455
Abstract
Polyetheretherketone (PEEK) is a biocompatible, chemically and physically stable radiolucent polymer that exhibits a similar elastic modulus to the normal human bone, making it an attractive orthopedic implant material. However, PEEK is biologically inert, preventing strong enough bonding with the surrounding bone tissue [...] Read more.
Polyetheretherketone (PEEK) is a biocompatible, chemically and physically stable radiolucent polymer that exhibits a similar elastic modulus to the normal human bone, making it an attractive orthopedic implant material. However, PEEK is biologically inert, preventing strong enough bonding with the surrounding bone tissue when implanted in vivo. Surface modification and composite preparation are the two main strategies for the improvement of the bioactivity of PEEK. In this study, the plasma activated PEEK surfaces with the embedded bioglass, chitosan, and bioglass-chitosan mixed layers applying from the solution dip-coating technique were investigated. The most prominent factors affecting the coating biocompatibility are strictly connected with the composition of its outer surface (its charge and functional groups), hydrophilic-hydrophobic character, wettability and surface free energy, and topography (size of pores/substructures, roughness, stiffness), as well as the personal characteristics of the patient. The obtained surfaces were examined in terms of wettability and surface-free energy changes. Additionally, FTIR (Fourier Transformation Infrared Spectrometry) and SIMS (Secondary Ion Mass Spectrometry) were applied to establish and control the coating composition. Simultaneously the structure of coatings was visualized with the aid of SEM (Scanning Electron Microscopy). Finally, the obtained systems were incubated in SBF (Simulated Body Fluid) to verify the modifications’ influence on the bioactivity/biocompatibility of the PEEK surface. Different structures with variable compositions, as well as changes of the wettability, were observed depending on the applied modification. In addition, the incubation in SBF suggested that the bioglass-chitosan ratio influenced the formation of apatite-like structures on the modified PEEK surfaces. Full article
(This article belongs to the Special Issue Chitosan, Chitosan Derivatives and Their Applications)
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18 pages, 2999 KiB  
Article
Effect of Storage and Drying Treatments on Antioxidant Activity and Phenolic Composition of Lemon and Clementine Peel Extracts
by Esther Gómez-Mejía, Iván Sacristán, Noelia Rosales-Conrado, María Eugenia León-González and Yolanda Madrid
Molecules 2023, 28(4), 1624; https://doi.org/10.3390/molecules28041624 - 8 Feb 2023
Cited by 15 | Viewed by 3343
Abstract
Obtaining polyphenols from horticultural waste is an emerging trend that enables the valorization of resources and the recovery of value-added compounds. However, a pivotal point in the exploitation of these natural extracts is the assessment of their chemical stability. Hence, this study evaluates [...] Read more.
Obtaining polyphenols from horticultural waste is an emerging trend that enables the valorization of resources and the recovery of value-added compounds. However, a pivotal point in the exploitation of these natural extracts is the assessment of their chemical stability. Hence, this study evaluates the effect of temperature storage (20 and −20 °C) and drying methods on the phenolic composition and antioxidant activity of clementine and lemon peel extracts, applying HPLC-DAD-MS, spectrophotometric methods, and chemometric tools. Vacuum-drying treatment at 60 °C proved to be rather suitable for retaining the highest antioxidant activity and the hesperidin, ferulic, and coumaric contents in clementine peel extracts. Lemon extracts showed an increase in phenolic acids after oven-drying at 40 °C, while hesperidin and rutin were sustained better at 60 °C. Hydroethanolic extracts stored for 90 days preserved antioxidant activity and showed an increase in the total phenolic and flavonoid contents in lemon peels, unlike in clementine peels. Additionally, more than 50% of the initial concentration was maintained up to 51 days, highlighting a half-life time of 71 days for hesperidin in lemon peels. Temperature was not significant in the preservation of the polyphenols evaluated, except for in rutin and gallic acid, thus, the extracts could be kept at 20 °C. Full article
(This article belongs to the Special Issue Antioxidant Activity of Plant Phenolics)
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19 pages, 1450 KiB  
Review
On-Site Detection of Volatile Organic Compounds (VOCs)
by Ruben Epping and Matthias Koch
Molecules 2023, 28(4), 1598; https://doi.org/10.3390/molecules28041598 - 7 Feb 2023
Cited by 86 | Viewed by 13185
Abstract
Volatile organic compounds (VOCs) are of interest in many different fields. Among them are food and fragrance analysis, environmental and atmospheric research, industrial applications, security or medical and life science. In the past, the characterization of these compounds was mostly performed via sample [...] Read more.
Volatile organic compounds (VOCs) are of interest in many different fields. Among them are food and fragrance analysis, environmental and atmospheric research, industrial applications, security or medical and life science. In the past, the characterization of these compounds was mostly performed via sample collection and off-site analysis with gas chromatography coupled to mass spectrometry (GC-MS) as the gold standard. While powerful, this method also has several drawbacks such as being slow, expensive, and demanding on the user. For decades, intense research has been dedicated to find methods for fast VOC analysis on-site with time and spatial resolution. We present the working principles of the most important, utilized, and researched technologies for this purpose and highlight important publications from the last five years. In this overview, non-selective gas sensors, electronic noses, spectroscopic methods, miniaturized gas chromatography, ion mobility spectrometry and direct injection mass spectrometry are covered. The advantages and limitations of the different methods are compared. Finally, we give our outlook into the future progression of this field of research. Full article
(This article belongs to the Special Issue Analytical Chemistry in Europe: Towards Sustainability and Quality of Life)
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22 pages, 1187 KiB  
Review
Glutathione-Related Enzymes and Proteins: A Review
by Janka Vašková, Ladislav Kočan, Ladislav Vaško and Pál Perjési
Molecules 2023, 28(3), 1447; https://doi.org/10.3390/molecules28031447 - 2 Feb 2023
Cited by 161 | Viewed by 15162
Abstract
The tripeptide glutathione is found in all eukaryotic cells, and due to the compartmentalization of biochemical processes, its synthesis takes place exclusively in the cytosol. At the same time, its functions depend on its transport to/from organelles and interorgan transport, in which the [...] Read more.
The tripeptide glutathione is found in all eukaryotic cells, and due to the compartmentalization of biochemical processes, its synthesis takes place exclusively in the cytosol. At the same time, its functions depend on its transport to/from organelles and interorgan transport, in which the liver plays a central role. Glutathione is determined as a marker of the redox state in many diseases, aging processes, and cell death resulting from its properties and reactivity. It also uses other enzymes and proteins, which enables it to engage and regulate various cell functions. This paper approximates the role of these systems in redox and detoxification reactions such as conjugation reactions of glutathione-S-transferases, glyoxylases, reduction of peroxides through thiol peroxidases (glutathione peroxidases, peroxiredoxins) and thiol–disulfide exchange reactions catalyzed by glutaredoxins. Full article
(This article belongs to the Special Issue Glutathione: Chemistry and Biochemistry)
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29 pages, 3532 KiB  
Review
Coordination Compounds of Cu, Zn, and Ni with Dicarboxylic Acids and N Donor Ligands, and Their Biological Activity: A Review
by Ivana Loubalová and Pavel Kopel
Molecules 2023, 28(3), 1445; https://doi.org/10.3390/molecules28031445 - 2 Feb 2023
Cited by 22 | Viewed by 4280
Abstract
Complexes of carboxylic acids are very often studied due to their interesting structural, spectral, and magnetic properties. This review is focused on complexes of four dicarboxylic acids, namely, 2,2′-thiodioacetic, 3,3′-thiodipropionic, 3,3′-dithiodipropionic, and fumaric acid. Many of the complexes were characterized by single crystal [...] Read more.
Complexes of carboxylic acids are very often studied due to their interesting structural, spectral, and magnetic properties. This review is focused on complexes of four dicarboxylic acids, namely, 2,2′-thiodioacetic, 3,3′-thiodipropionic, 3,3′-dithiodipropionic, and fumaric acid. Many of the complexes were characterized by single crystal X-ray analyses. Without the analyses, it is very difficult to predict the coordination mode of carboxylate groups or nitrogen ligands on central atoms. Thus, structural properties are also discussed, as well as potential applications. Full article
(This article belongs to the Special Issue Metal-Based Complex: Preparation and Medicinal Characteristics)
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12 pages, 2491 KiB  
Article
Hydrogen Absorption Reactions of Hydrogen Storage Alloy LaNi5 under High Pressure
by Toyoto Sato, Hiroyuki Saitoh, Reina Utsumi, Junya Ito, Yuki Nakahira, Kazuki Obana, Shigeyuki Takagi and Shin-ichi Orimo
Molecules 2023, 28(3), 1256; https://doi.org/10.3390/molecules28031256 - 27 Jan 2023
Cited by 30 | Viewed by 6519
Abstract
Hydrogen can be stored in the interstitial sites of the lattices of intermetallic compounds. To date, intermetallic compound LaNi5 or related LaNi5-based alloys are known to be practical hydrogen storage materials owing to their higher volumetric hydrogen densities, making them [...] Read more.
Hydrogen can be stored in the interstitial sites of the lattices of intermetallic compounds. To date, intermetallic compound LaNi5 or related LaNi5-based alloys are known to be practical hydrogen storage materials owing to their higher volumetric hydrogen densities, making them a compact hydrogen storage method and allowing stable reversible hydrogen absorption and desorption reactions to take place at room temperature below 1.0 MPa. By contrast, gravimetric hydrogen density is required for key improvements (e.g., gravimetric hydrogen density of LaNi5: 1.38 mass%). Although hydrogen storage materials have typically been evaluated for their hydrogen storage properties below 10 MPa, reactions between hydrogen and materials can be facilitated above 1 GPa because the chemical potential of hydrogen dramatically increases at a higher pressure. This indicates that high-pressure experiments above 1 GPa could clarify the latent hydrogen absorption reactions below 10 MPa and potentially explore new hydride phases. In this study, we investigated the hydrogen absorption reaction of LaNi5 above 1 GPa at room temperature to understand their potential hydrogen storage capacities. The high-pressure experiments on LaNi5 with and without an internal hydrogen source (BH3NH3) were performed using a multi-anvil-type high-pressure apparatus, and the reactions were observed using in situ synchrotron radiation X-ray diffraction with an energy dispersive method. The results showed that 2.07 mass% hydrogen was absorbed by LaNi5 at 6 GPa. Considering the unit cell volume expansion, the estimated hydrogen storage capacity could be 1.5 times higher than that obtained from hydrogen absorption reaction below 1.0 MPa at 303 K. Thus, 33% of the available interstitial sites in LaNi5 remained unoccupied by hydrogen atoms under conventional conditions. Although the hydrogen-absorbed LaNi5Hx (x < 9) was maintained below 573 K at 10 GPa, LaNi5Hx began decomposing into NiH, and the formation of a new phase was observed at 873 K and 10 GPa. The new phase was indexed to a hexagonal or trigonal unit cell with a ≈ 4.44 Å and c ≈ 8.44 Å. Further, the newly-formed phase was speculated to be a new hydride phase because the Bragg peak positions and unit cell parameters were inconsistent with those reported for the La-Ni intermetallic compounds and La-Ni hydride phases. Full article
(This article belongs to the Special Issue Advances in Hydrogen Storage Materials for Energy Utilization 2.0)
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52 pages, 1446 KiB  
Review
Transporter-Mediated Drug Delivery
by Gergely Gyimesi and Matthias A. Hediger
Molecules 2023, 28(3), 1151; https://doi.org/10.3390/molecules28031151 - 24 Jan 2023
Cited by 40 | Viewed by 8705
Abstract
Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly [...] Read more.
Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters. Full article
(This article belongs to the Special Issue Transporter-Mediated Drug Delivery)
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16 pages, 2034 KiB  
Article
Fish By-Products: A Source of Enzymes to Generate Circular Bioactive Hydrolysates
by Sandra Borges, Joana Odila, Glenise Voss, Rui Martins, Ana Rosa, José António Couto, André Almeida and Manuela Pintado
Molecules 2023, 28(3), 1155; https://doi.org/10.3390/molecules28031155 - 24 Jan 2023
Cited by 31 | Viewed by 4404
Abstract
Fish viscera are usually discarded as waste, causing environmental problems, or as low-value by-products. This study describes a self-sufficient and zero waste approach to obtain enzymes and protein hydrolysates from fish by-products. Firstly, recovery steps of viscera enzymatic extract were applied, and the [...] Read more.
Fish viscera are usually discarded as waste, causing environmental problems, or as low-value by-products. This study describes a self-sufficient and zero waste approach to obtain enzymes and protein hydrolysates from fish by-products. Firstly, recovery steps of viscera enzymatic extract were applied, and the resulting raw extract was stable at a pH range of 8–9 and at temperatures between 40 and 50 °C. The application of the extracted enzymes and alcalase on fish by-products hydrolysis was also determined. The selected conditions for the enzymatic hydrolysis were 10% (E/S) for 6 h using viscera enzymatic extract and 3% (E/S) for 2 h using alcalase. Fish protein hydrolysates (FPH) proved to have a notable antioxidant capacity with similar activity, ~11 mg ascorbic acid/g dry extract (ABTS assay) and ~150 mg Trolox/g dry extract (ORAC assay). FPH were also able to inhibit the angiotensin-converting enzyme, however, alcalase hydrolysates revealed a higher antihypertensive potential, IC50 of 101 µg of protein/mL. In general, FPH obtained by both enzymes systems maintained these bioactivities after the passage throughout a simulated gastrointestinal tract. The hydrolysates also displayed important technological properties, namely oil absorption capacity (~1 g oil/g sample) and emulsifying property (~40%). Therefore, it will be conceivable to use fish by-products based on a circular economy approach to generate added value compounds for animal and human nutrition. Full article
(This article belongs to the Special Issue Bioproducts for Health III)
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15 pages, 3895 KiB  
Review
Synthesis of Sulfoximines and Sulfonimidamides Using Hypervalent Iodine Mediated NH Transfer
by Renzo Luisi and James A. Bull
Molecules 2023, 28(3), 1120; https://doi.org/10.3390/molecules28031120 - 22 Jan 2023
Cited by 24 | Viewed by 9108
Abstract
The development of NH transfer reactions using hypervalent iodine and simple sources of ammonia has facilitated the synthesis of sulfoximines and sulfonimidamides for applications across the chemical sciences. Perhaps most notably, the methods have been widely applied in medicinal chemistry and in the [...] Read more.
The development of NH transfer reactions using hypervalent iodine and simple sources of ammonia has facilitated the synthesis of sulfoximines and sulfonimidamides for applications across the chemical sciences. Perhaps most notably, the methods have been widely applied in medicinal chemistry and in the preparation of biologically active compounds, including in the large-scale preparation of an API intermediate. This review provides an overview of the development of these synthetic methods involving an intermediate iodonitrene since our initial report in 2016 on the conversion of sulfoxides into sulfoximines. This review covers the NH transfer to sulfoxides and sulfinamides, and the simultaneous NH/O transfer to sulfides and sulfenamides to form sulfoximines and sulfonimidamides, respectively. The mechanism of the reactions and the identification of key intermediates are discussed. Developments in the choice of reagents, and in the reaction conditions and setups used are described. Full article
(This article belongs to the Special Issue A Themed Issue Dedicated to Professor Carsten Bolm—Sulfoximines and Related Sulfur Compounds and Their Biological Applications)
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16 pages, 2681 KiB  
Article
Zinc-Catalyzed Enantioselective [3 + 3] Annulation for Synthesis of Chiral Spiro[indoline-3,4′-thiopyrano[2,3-b]indole] Derivatives
by Tian-Tian Liu, Yu Chen, Guang-Jian Mei, Yuan-Zhao Hua, Shi-Kun Jia and Min-Can Wang
Molecules 2023, 28(3), 1056; https://doi.org/10.3390/molecules28031056 - 20 Jan 2023
Cited by 16 | Viewed by 2323
Abstract
With a dinuclear zinc-ProPhenol complex as a catalyst, an efficient and novel [3 + 3] annulation of indoline-2-thiones and isatylidene malononitriles has been successfully developed via the Brønsted base and Lewis acid cooperative activation model. This practical methodology gives access to a broad [...] Read more.
With a dinuclear zinc-ProPhenol complex as a catalyst, an efficient and novel [3 + 3] annulation of indoline-2-thiones and isatylidene malononitriles has been successfully developed via the Brønsted base and Lewis acid cooperative activation model. This practical methodology gives access to a broad range of chiral spiro[indoline-3,4′-thiopyrano[2,3-b]indole] derivatives in good yields with excellent levels of enantioselectivities (up to 88% yield and 99% ee). Full article
(This article belongs to the Special Issue Recent Advances of Catalytic Asymmetric Synthesis)
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39 pages, 10204 KiB  
Review
Structural Features of Small Molecule Antioxidants and Strategic Modifications to Improve Potential Bioactivity
by Nathan C. Charlton, Maxim Mastyugin, Béla Török and Marianna Török
Molecules 2023, 28(3), 1057; https://doi.org/10.3390/molecules28031057 - 20 Jan 2023
Cited by 99 | Viewed by 7743
Abstract
This review surveys the major structural features in various groups of small molecules that are considered to be antioxidants, including natural and synthetic compounds alike. Recent advances in the strategic modification of known small molecule antioxidants are also described. The highlight is placed [...] Read more.
This review surveys the major structural features in various groups of small molecules that are considered to be antioxidants, including natural and synthetic compounds alike. Recent advances in the strategic modification of known small molecule antioxidants are also described. The highlight is placed on changing major physicochemical parameters, including log p, bond dissociation energy, ionization potential, and others which result in improved antioxidant activity. Full article
(This article belongs to the Special Issue Featured Reviews in Organic Chemistry)
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14 pages, 2195 KiB  
Article
The Halogen Bond in Weakly Bonded Complexes and the Consequences for Aromaticity and Spin-Orbit Coupling
by Ana V. Cunha, Remco W. A. Havenith, Jari van Gog, Freija De Vleeschouwer, Frank De Proft and Wouter Herrebout
Molecules 2023, 28(2), 772; https://doi.org/10.3390/molecules28020772 - 12 Jan 2023
Cited by 16 | Viewed by 3301
Abstract
The halogen bond complexes CF3X⋯Y and C2F3X⋯Y, with Y = furan, thiophene, selenophene and X = Cl, Br, I, have been studied by using DFT and CCSD(T) in order to understand which factors govern the interaction between [...] Read more.
The halogen bond complexes CF3X⋯Y and C2F3X⋯Y, with Y = furan, thiophene, selenophene and X = Cl, Br, I, have been studied by using DFT and CCSD(T) in order to understand which factors govern the interaction between the halogen atom X and the aromatic ring. We found that PBE0-dDsC/QZ4P gives an adequate description of the interaction energies in these complexes, compared to CCSD(T) and experimental results. The interaction between the halogen atom X and the π-bonds in perpendicular orientation is stronger than the interaction with the in-plane lone pairs of the heteroatom of the aromatic cycle. The strength of the interaction follows the trend Cl < Br < I; the chalcogenide in the aromatic ring nor the hybridization of the C–X bond play a decisive role. The energy decomposition analysis shows that the interaction energy is dominated by all three contributions, viz., the electrostatic, orbital, and dispersion interactions: not one factor dominates the interaction energy. The aromaticity of the ring is undisturbed upon halogen bond formation: the π-ring current remains equally strong and diatropic in the complex as it is for the free aromatic ring. However, the spin-orbit coupling between the singlet and triplet π→π* states is increased upon halogen bond formation and a faster intersystem crossing between these states is therefore expected. Full article
(This article belongs to the Special Issue Chemical Bond and Intermolecular Interactions)
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34 pages, 2478 KiB  
Review
Leaky Gut and the Ingredients That Help Treat It: A Review
by Ricardo Santos Aleman, Marvin Moncada and Kayanush J. Aryana
Molecules 2023, 28(2), 619; https://doi.org/10.3390/molecules28020619 - 7 Jan 2023
Cited by 112 | Viewed by 44167
Abstract
The human body is in daily contact with potentially toxic and infectious substances in the gastrointestinal tract (GIT). The GIT has the most significant load of antigens. The GIT can protect the intestinal integrity by allowing the passage of beneficial agents and blocking [...] Read more.
The human body is in daily contact with potentially toxic and infectious substances in the gastrointestinal tract (GIT). The GIT has the most significant load of antigens. The GIT can protect the intestinal integrity by allowing the passage of beneficial agents and blocking the path of harmful substances. Under normal conditions, a healthy intestinal barrier prevents toxic elements from entering the blood stream. However, factors such as stress, an unhealthy diet, excessive alcohol, antibiotics, and drug consumption can compromise the composition of the intestinal microbiota and the homeostasis of the intestinal barrier function of the intestine, leading to increased intestinal permeability. Intestinal hyperpermeability can allow the entry of harmful agents through the junctions of the intestinal epithelium, which pass into the bloodstream and affect various organs and systems. Thus, leaky gut syndrome and intestinal barrier dysfunction are associated with intestinal diseases, such as inflammatory bowel disease and irritable bowel syndrome, as well as extra-intestinal diseases, including heart diseases, obesity, type 1 diabetes mellitus, and celiac disease. Given the relationship between intestinal permeability and numerous conditions, it is convenient to seek an excellent strategy to avoid or reduce the increase in intestinal permeability. The impact of dietary nutrients on barrier function can be crucial for designing new strategies for patients with the pathogenesis of leaky gut-related diseases associated with epithelial barrier dysfunctions. In this review article, the role of functional ingredients is suggested as mediators of leaky gut-related disorders. Full article
(This article belongs to the Special Issue Physicochemical Study of Foods)
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32 pages, 26676 KiB  
Review
Mechanistic Aspects of the Electrochemical Oxidation of Aliphatic Amines and Aniline Derivatives
by Ashwin K. V. Mruthunjaya and Angel A. J. Torriero
Molecules 2023, 28(2), 471; https://doi.org/10.3390/molecules28020471 - 4 Jan 2023
Cited by 36 | Viewed by 7646
Abstract
The electrochemical oxidation of amines is an essential alternative to the conventional chemical transformation that provides critical routes for synthesising and modifying a wide range of chemically useful molecules, including pharmaceuticals and agrochemicals. As a result, the anodic reactivity of these compounds has [...] Read more.
The electrochemical oxidation of amines is an essential alternative to the conventional chemical transformation that provides critical routes for synthesising and modifying a wide range of chemically useful molecules, including pharmaceuticals and agrochemicals. As a result, the anodic reactivity of these compounds has been extensively researched over the past seven decades. However, the different mechanistic aspects of the electrochemical oxidation of amines have never been discussed from a comprehensive and general point of view. This review examines the oxidation mechanism of aliphatic amines, amides, aniline and aniline derivatives, carbamates, and lactams, either directly oxidised at different electrode surfaces or indirectly oxidised by a reversible redox molecule, in which the reactive form was generated in situ. The mechanisms are compared and simplified to understand all possible pathways for the oxidation of amines using only a few general mechanisms. Examples of the application of these oxidation reactions are also provided. Full article
(This article belongs to the Special Issue Exclusive Feature Papers in Electrochemistry)
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19 pages, 4318 KiB  
Article
Extraction of Bioactive Compounds from C. vulgaris Biomass Using Deep Eutectic Solvents
by Maria Myrto Dardavila, Sofia Pappou, Maria G. Savvidou, Vasiliki Louli, Petros Katapodis, Haralambos Stamatis, Kostis Magoulas and Epaminondas Voutsas
Molecules 2023, 28(1), 415; https://doi.org/10.3390/molecules28010415 - 3 Jan 2023
Cited by 29 | Viewed by 4317
Abstract
C. vulgaris microalgae biomass was employed for the extraction of valuable bioactive compounds with deep eutectic-based solvents (DESs). Particularly, the Choline Chloride (ChCl) based DESs, ChCl:1,2 butanediol (1:4), ChCl:ethylene glycol (1:2), and ChCl:glycerol (1:2) mixed with water at 70/30 w/w ratio [...] Read more.
C. vulgaris microalgae biomass was employed for the extraction of valuable bioactive compounds with deep eutectic-based solvents (DESs). Particularly, the Choline Chloride (ChCl) based DESs, ChCl:1,2 butanediol (1:4), ChCl:ethylene glycol (1:2), and ChCl:glycerol (1:2) mixed with water at 70/30 w/w ratio were used for that purpose. The extracts’ total carotenoid (TCC) and phenolic contents (TPC), as well as their antioxidant activity (IC50), were determined within the process of identification of the most efficient solvent. This screening procedure revealed ChCl:1,2 butanediol (1:4)/H2O 70/30 w/w as the most compelling solvent; thus, it was employed thereafter for the extraction process optimization. Three extraction parameters, i.e., solvent-to-biomass ratio, temperature, and time were studied regarding their impact on the extract’s TCC, TPC, and IC50. For the experimental design and process optimization, the statistical tool Response Surface Methodology was used. The resulting models’ predictive capacity was confirmed experimentally by carrying out two additional extractions under conditions different from the experimental design. Full article
(This article belongs to the Special Issue Ionic Liquids and Deep Eutectic Solvents: Greener Approaches for Sustainable Chemistry)
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13 pages, 1337 KiB  
Review
Tyrosinase Inhibitors Naturally Present in Plants and Synthetic Modifications of These Natural Products as Anti-Melanogenic Agents: A Review
by Mubashir Hassan, Saba Shahzadi and Andrzej Kloczkowski
Molecules 2023, 28(1), 378; https://doi.org/10.3390/molecules28010378 - 2 Jan 2023
Cited by 55 | Viewed by 10114
Abstract
Tyrosinase is a key enzyme target to design new chemical ligands against melanogenesis. In the current review, different chemical derivatives are explored which have been used as anti-melanogenic compounds. These are different chemical compounds naturally present in plants and semi-synthetic and synthetic compounds [...] Read more.
Tyrosinase is a key enzyme target to design new chemical ligands against melanogenesis. In the current review, different chemical derivatives are explored which have been used as anti-melanogenic compounds. These are different chemical compounds naturally present in plants and semi-synthetic and synthetic compounds inspired by these natural products, such as kojic acid produced by several species of fungi; arbutin—a glycosylated hydroquinone extracted from the bearberry plant; vanillin—a phenolic aldehyde extracted from the vanilla bean, etc. After enzyme inhibition screening, various chemical compounds showed different therapeutic effects as tyrosinase inhibitors with different values of the inhibition constant and IC50. We show how appropriately designed scaffolds inspired by the structures of natural compounds are used to develop novel synthetic inhibitors. We review the results of numerous studies, which could lead to the development of effective anti-tyrosinase agents with increased efficiency and safety in the near future, with many applications in the food, pharmaceutical and cosmetics industries. Full article
(This article belongs to the Special Issue Natural Product-Inspired Molecules: From Weed to Remedy)
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