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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products Chemistry".

Deadline for manuscript submissions: closed (31 October 2020) | Viewed by 43823

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Prof. Dr. Thomas J. Schmidt

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Institute of Pharmaceutical Biology and Phytochemistry, University of Münster, Corrensstrasse 48, D-48149 Münster, Germany
Interests: natural products; anti-parasitic activity; anti-cancer activity; structure elucidation; spectroscopy; computer-aided structure-activity relationship studies
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Dear Colleagues,

This Special Issue of Molecules is dedicated to recent advances in the research area of natural products chemistry and comprises a selection of exclusive papers of the Editorial Board Members (EBMs) of the Natural Products Chemistry Section. This section collects either research articles highlighting interesting results of the research groups of our section’s EBMs or review articles in which our section’s EBMs discuss key topics in the field. This Special Issue aims to represent our section as an attractive open-access publishing platform for natural products chemistry research.

Prof. Dr. Thomas J. Schmidt
Guest Editor

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Published Papers (10 papers)

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Research

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12 pages, 9059 KiB

Open AccessArticle

Pectin-Based Formulations for Controlled Release of an Ellagic Acid Salt with High Solubility Profile in Physiological Media

by Marco Aldo Ortenzi, Stefano Antenucci, Stefania Marzorati, Lucia Panzella, Silvia Molino, José Ángel Rufián-Henares, Alessandra Napolitano and Luisella Verotta

Molecules 2021, 26(2), 433; https://doi.org/10.3390/molecules26020433 - 15 Jan 2021

Cited by 8 | Viewed by 2345

Abstract

Among bioactive phytochemicals, ellagic acid (EA) is one of the most controversial because its high antioxidant and cancer-preventing effects are strongly inhibited by low gastrointestinal absorption and rapid excretion. Strategies toward an increase of solubility in water and bioavailability, while preserving its structural integrity and warranting its controlled release at the physiological targets, are therefore largely pursued. In this work, EA lysine salt at 1:4 molar ratio (EALYS), exhibiting a more than 400 times increase of water solubility with respect to literature reports, was incorporated at 10% in low methoxylated (LM) and high methoxylated (HM) pectin films. The release of EA in PBS at pH 7.4 from both film preparations was comparable and reached 15% of the loaded compound over 2 h. Under simulated gastric conditions, release of EA from HM and LM pectin films was minimal at gastric pH, whereas higher concentrations—up to 300 μM, corresponding to ca. 50% of the overall content—were obtained in the case of the HM pectin film after 2 h incubation at the slightly alkaline pH of small intestine environment, with the enzyme and bile salt components enhancing the release. EALYS pectin films showed a good prebiotic activity as evaluated by determination of short chain fatty acids (SCFAs) levels following microbial fermentation, with a low but significant increase of the effects produced by the pectins themselves. Overall, these results highlight pectin films loaded with EALYS salt as a promising formulation to improve administration and controlled release of the compound. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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23 pages, 4115 KiB

Open AccessFeature PaperArticle

Nicotine Changes Airway Epithelial Phenotype and May Increase the SARS-COV-2 Infection Severity

by Leonardo Lupacchini, Fabrizio Maggi, Carlo Tomino, Chiara De Dominicis, Cristiana Mollinari, Massimo Fini, Stefano Bonassi, Daniela Merlo and Patrizia Russo

Molecules 2021, 26(1), 101; https://doi.org/10.3390/molecules26010101 - 28 Dec 2020

Cited by 13 | Viewed by 3853

Abstract

(1) Background: Nicotine is implicated in the SARS-COV-2 infection through activation of the α7-nAChR and over-expression of ACE2. Our objective was to clarify the role of nicotine in SARS-CoV-2 infection exploring its molecular and cellular activity. (2) Methods: HBEpC or si-mRNA-α7-HBEpC were treated for 1 h, 48 h or continuously with 10⁻⁷ M nicotine, a concentration mimicking human exposure to a cigarette. Cell viability and proliferation were evaluated by trypan blue dye exclusion and cell counting, migration by cell migration assay, senescence by SA-β-Gal activity, and anchorage-independent growth by cloning in soft agar. Expression of Ki67, p53/phospho-p53, VEGF, EGFR/pEGFR, phospho-p38, intracellular Ca²⁺, ATP and EMT were evaluated by ELISA and/or Western blotting. (3) Results: nicotine induced through α7-nAChR (i) increase in cell viability, (ii) cell proliferation, (iii) Ki67 over-expression, (iv) phospho-p38 up-regulation, (v) EGFR/pEGFR over-expression, (vi) increase in basal Ca²⁺ concentration, (vii) reduction of ATP production, (viii) decreased level of p53/phospho-p53, (ix) delayed senescence, (x) VEGF increase, (xi) EMT and consequent (xii) enhanced migration, and (xiii) ability to grow independently of the substrate. (4) Conclusions: Based on our results and on evidence showing that nicotine potentiates viral infection, it is likely that nicotine is involved in SARS-CoV-2 infection and severity. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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31 pages, 3429 KiB

Open AccessArticle

Vapors of Volatile Plant-Derived Products Significantly Affect the Results of Antimicrobial, Antioxidative and Cytotoxicity Microplate-Based Assays

by Marketa Houdkova, Genesis Albarico, Ivo Doskocil, Jan Tauchen, Klara Urbanova, Edgardo E. Tulin and Ladislav Kokoska

Molecules 2020, 25(24), 6004; https://doi.org/10.3390/molecules25246004 - 18 Dec 2020

Cited by 10 | Viewed by 2734

Abstract

Volatile plant-derived products were observed to exhibit broad spectrum of biological effects. However, due to their volatility, results of conventional microplate-based bioassays can be significantly affected by the vapors. With aim to demonstrate this phenomenon, antimicrobial, antioxidant, and cytotoxic activities of three essential oils (Alpinia elegans, Cinnamomum iners, and Xanthostemon verdugonianus), one supercritical CO₂ extract (Nigella sativa), and four plant-derived compounds (capsaicin, caryophyllene oxide, 8-hydroxyquinoline, and thymoquinone) were evaluated in series of experiments including both ethylene vinyl acetate (EVA) Capmat sealed and nonsealed microplates. The results clearly illustrate that vapor transition to adjoining wells causes false-positive results of bioassays performed in nonsealed microtiter plates. The microplate layout and a duration of the assay were demonstrated as the key aspects defining level of the results affection by the vapors of volatile agents. Additionally, we reported biological activities and chemical composition of essential oils from A. elegans seeds and X. verdugonianus leaves, which were, according to our best knowledge, analyzed for the first time. Considering our findings, certain modifications of conventional microplate-based assays are necessary (e.g., using EVA Capmat as vapor barrier) to obtain reliable results when biological properties of volatile agents are evaluated. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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11 pages, 1071 KiB

Open AccessArticle

Development and Validation of a TLC-Densitometry Method for Histamine Monitoring in Fish and Fishery Products

by Ayoub Kounnoun, Adnane Louajri, Francesco Cacciola, Hafssa El Cadi, Hajar Bougtaib, Naoual Alahlah, Aicha El Baaboua and Mohamed El Maadoudi

Molecules 2020, 25(16), 3611; https://doi.org/10.3390/molecules25163611 - 08 Aug 2020

Cited by 18 | Viewed by 3672

Abstract

Histamine poisoning is a significant public health problem. Therefore, the monitoring of histamine content in fish and fishery products is considered to be a crucial measure in the seafood industry. In the present study, a simple and rapid densitometric thin-layer chromatographic (TLC) method for histamine determination in fish samples was developed and validated. The samples were homogenized with 10% trichloroacetic acid and histamine was efficiently extracted. Then, an appropriate derivatization procedure was adopted with dansyl chloride. Once the derivatization was carried out, the samples were applied to silica gel TLC plates and developed by ascending chromatography with chloroform-triethylamine (6:4, v/v) as the mobile phase. The intensity of the histamine-dansyl derivative spots was measured by densitometry at 365 nm, and the quantitation was performed by BIO-1D image processing software. The validation of this method revealed good linearity and specificity over a concentration range from 6.25 to 100 mg/kg. Adequate precision was shown by relative standard deviations (RSD) smaller than 4.82%, accuracy ranged from −6.88% to 5.28%, and satisfactory recoveries ranging from 93% to 105% were obtained. The Limit of Detection and the Limit of Quantification were calculated at 4.4 mg/kg and 10.5 mg/kg, respectively. In addition, the effectiveness of the proposed method was assessed by the analysis of various samples, and the obtained results were confirmed with those achieved by the HPLC-UV method. Moreover, the developed method was found to be simple, cheap, and suitable for application to analyze several samples simultaneously. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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18 pages, 1785 KiB

Open AccessArticle

Formulation of a Phenol-Rich Extract from Unripe Olives (Olea europaea L.) in Microemulsion to Improve Its Solubility and Intestinal Permeability

by Lorenzo Cecchi, Vieri Piazzini, Mario D’Ambrosio, Cristina Luceri, Federica Rocco, Marzia Innocenti, Giulia Vanti, Nadia Mulinacci and Maria Camilla Bergonzi

Molecules 2020, 25(14), 3198; https://doi.org/10.3390/molecules25143198 - 13 Jul 2020

Cited by 13 | Viewed by 2658

Abstract

The beneficial properties of phenolic compounds from Olea europaea L. are well-known. An olive extract (OE) was prepared from unripe olives (Moraiolo cultivar). The study aimed to formulate OE into a microemulsion (ME) in oral dosage form. OE was extracted from olives with EtOH:H₂O (80:20) and characterized by HPLC-DAD. ME composition was stated by a solubility and pseudo-ternary diagram. The ME was chemically and physically characterized, and its stability at 4 °C was analyzed for three months. The ability of the formulation to ameliorate the solubility and the intestinal permeability of OE was evaluated by a Parallel Artificial Membrane Permeability Assay (PAMPA) assay and Caco-2 cells. The total phenolic content of the extract was 39% w/w. The main constituent was oleuropein (31.0%), together with ligstroside (3.1%) and verbascoside (2.4%). The ME was prepared using Capryol 90 as the oily phase, and Cremophor EL and Transcutol (2:1) as surfactant and co-surfactant, respectively. ME droplet size was 14.03 ± 1.36 nm, PdI 0.20 ± 0.08, ζ-potential −1.16 ± 0.48. Stability of ME was confirmed for at least three months. The formulation was loaded with 35 mg/mL of OE, increasing the solubility of the extract by about four times. The enhanced permeability of OE was evaluated by PAMPA, as demonstrated by the Pe value (1.44 ± 0.83 × 10⁻⁶ cm/s for OE hydroalcoholic solution, 3.74 ± 0.34 × 10⁻⁶ cm/s for OE-ME). Caco-2 cell transport studies confirmed the same results: P_app was 16.14 ± 0.05 × 10⁻⁶ cm/s for OE solution and 26.99 ± 0.45 × 10⁻⁶ cm/s for OE-ME. ME proved to be a suitable formulation for oral delivery. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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13 pages, 1294 KiB

Open AccessArticle

Synthesis and Antibacterial Analysis of Analogues of the Marine Alkaloid Pseudoceratidine

by David Barker, Stephanie Lee, Kyriakos G. Varnava, Kevin Sparrow, Michelle van Rensburg, Rebecca C. Deed, Melissa M. Cadelis, Steven A. Li, Brent R. Copp, Vijayalekshmi Sarojini and Lisa I. Pilkington

Molecules 2020, 25(11), 2713; https://doi.org/10.3390/molecules25112713 - 11 Jun 2020

Cited by 6 | Viewed by 3211

Abstract

In an effort to gain more understanding on the structure activity relationship of pseudoceratidine 1, a di-bromo pyrrole spermidine alkaloid derived from the marine sponge Pseudoceratina purpurea that has been shown to exhibit potent biofouling, anti-fungal, antibacterial, and anti-malarial activities, a large series of 65 compounds that incorporated several aspects of structural variation has been synthesised through an efficient, divergent method that allowed for a number of analogues to be generated from common precursors. Subsequently, all analogues were assessed for their antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Overall, several compounds exhibited comparable or better activity than that of pseudoceratidine 1, and it was found that this class of compounds is generally more effective against Gram-positive than Gram-negative bacteria. Furthermore, altering several structural features allowed for the establishment of a comprehensive structure activity relationship (SAR), where it was concluded that several structural features are critical for potent anti-bacterial activity, including di-halogenation (preferable bromine, but chlorine is also effective) on the pyrrole ring, two pyrrolic units in the structure and with one or more secondary amines in the chain adjoining these units, with longer chains giving rise to better activities. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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13 pages, 653 KiB

Open AccessFeature PaperArticle

Sedative and Anxiolytic Activities of Opuntia ficus indica (L.) Mill.: An Experimental Assessment in Mice

by Esra Küpeli Akkol, Mert Ilhan, Büşra Karpuz, Yasin Genç and Eduardo Sobarzo-Sánchez

Molecules 2020, 25(8), 1844; https://doi.org/10.3390/molecules25081844 - 16 Apr 2020

Cited by 20 | Viewed by 3896

Abstract

Ethnobotanical field surveys revealed the use of fruits of Opuntia ficus indica (L.) Mill. for treating diabetes, burns, bronchial asthma, constipation, kidney stones, and rheumatic pains and as a sedative in Turkish folk medicine. This study aimed to verify the efficacy of the fruits of O. ficus indica experimentally and to define components responsible for the activity using bioassay-guided procedures. The crude methanolic extract of the fruits was sequentially fractionated into five subextracts: n-hexane, dichloromethane, ethyl acetate, n-butanol, and water. Further experiments were carried out on the most active subextract, that is, the ethyl acetate (EtOAc) subextract, which was further subjected to fractionation through successive column chromatographic applications on Sephadex LH-20. For activity assessment, each extract or fraction was submitted to bioassay systems; traction test, fireplace test, hole-board test, elevated plus-maze test, and open-field test were used for sedative and anxiolytic effects, and a thiopental-induced sleeping test was used for the hypnotic effect. Among the subextracts obtained from the methanolic extract, the EtOAc subextract showed significant sedative and anxiolytic effects in the bioassay systems. From the EtOAc subextract, major components were isolated, and their structures were determined as isorhamnetin, isorhamnetin 3-O-glucoside, isorhamnetin 3-O-rutinoside, and kaempferol 3-O-rutinoside using spectral techniques. In conclusion, this study confirmed the claimed use of the plant against anxiety in Turkish folk medicine. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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Review

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42 pages, 1930 KiB

Open AccessReview

Colored Corn: An Up-Date on Metabolites Extraction, Health Implication, and Potential Use

by Raffaella Colombo, Lucia Ferron and Adele Papetti

Molecules 2021, 26(1), 199; https://doi.org/10.3390/molecules26010199 - 02 Jan 2021

Cited by 42 | Viewed by 5086

Abstract

Colored (orange, pink, red, purple, and blue) corn strongly attracted attention on its healthy properties mainly due to its anthocyanin and carotenoid composition which is also responsible for its pigmentation. The present review summarized the recent updates on the extraction and chemical characterization of the main plant secondary metabolites present in colored seeds, kernel, cob, husk, and silk. The main approaches used to stabilize the extracts have been discussed as well as their food and non-food uses. Both in vitro and in vivo (animal models) studies on the different effects (antibacterial, antimutagenic, antioxidant, and anti-inflammatory activities, effects on metabolic syndrome, diabetes, glucose and lipidic metabolism, and neuroprotection) of pigmented extracts on animal and human health have been summarized. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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41 pages, 6276 KiB

Open AccessReview

Naturally-Occurring Alkaloids of Plant Origin as Potential Antimicrobials against Antibiotic-Resistant Infections

by Bruno Casciaro, Laura Mangiardi, Floriana Cappiello, Isabella Romeo, Maria Rosa Loffredo, Antonia Iazzetti, Andrea Calcaterra, Antonella Goggiamani, Francesca Ghirga, Maria Luisa Mangoni, Bruno Botta and Deborah Quaglio

Molecules 2020, 25(16), 3619; https://doi.org/10.3390/molecules25163619 - 09 Aug 2020

Cited by 42 | Viewed by 10682

Abstract

Antibiotic resistance is now considered a worldwide problem that puts public health at risk. The onset of bacterial strains resistant to conventional antibiotics and the scarcity of new drugs have prompted scientific research to re-evaluate natural products as molecules with high biological and chemical potential. A class of natural compounds of significant importance is represented by alkaloids derived from higher plants. In this review, we have collected data obtained from various research groups on the antimicrobial activities of these alkaloids against conventional antibiotic-resistant strains. In addition, the structure–function relationship was described and commented on, highlighting the high potential of alkaloids as antimicrobials. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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19 pages, 945 KiB

Open AccessFeature PaperReview

Plant In Vitro Systems as a Sustainable Source of Active Ingredients for Cosmeceutical Application

by Andrey S. Marchev and Milen I. Georgiev

Molecules 2020, 25(9), 2006; https://doi.org/10.3390/molecules25092006 - 25 Apr 2020

Cited by 17 | Viewed by 4893

Abstract

Cosmeceuticals are hybrids between cosmetics and pharmaceuticals which are being designed for a dual purpose: (1) To provide desired esthetical effects and (2) simultaneously treat dermatological conditions. The increased demand for natural remedies and the trends to use natural and safe ingredients resulted in intensive cultivation of medicinal plants. However, in many cases the whole process of plant cultivation, complex extraction procedure, and purification of the targeted molecules are not economically feasible. Therefore, the desired production of natural cosmetic products in sustainable and controllable fashion in the last years led to the intensive utilization of plant cell culture technology. The present review aims to highlight examples of biosynthesis of active ingredients derived through plant in vitro systems with potential cosmeceutical application. The exploitation of different type of extracts used in a possible cosmeceutical formulation, as well as, their activity tested in in vitro/in vivo models is thoroughly discussed. Furthermore, opportunities to manipulate the biosynthetic pathway, hence engineering the biosynthesis of some secondary metabolites, such as anthocyanins, have been highlighted. Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members of the Natural Products Chemistry Section of Molecules)

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