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Special Issue "Natural Secondary Metabolites"

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

Deadline for manuscript submissions: closed (30 June 2020).

Special Issue Editors

Dr. Anna Andolfi
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Guest Editor
Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario Monte S. Angelo Via Cintia 4, I-80126 Naples, Italy
Interests: isolation and structure elucidation of bioactive natural compounds from microorganisms and plants; chromatographic techniques; chemical derivatization; analytical and spectroscopic techniques
Special Issues and Collections in MDPI journals
Dr. Maria Michela Salvatore
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Assistant Guest Editor
Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario Monte S. Angelo Via Cintia 4, I-80126 Naples, Italy
Interests: isolation and structure elucidation of bioactive natural compounds from microorganisms and plants; chromatographic techniques; mass spectrometry

Special Issue Information

Dear Colleagues,

Since ancient times, secondary metabolites that are produced by plants, animals, fungi, and microorganisms have been used for their interesting properties as medical substances, poisons, dyes, antimicrobials, insecticides, flavouring substances, etc.

As is well known, a vast and diverse assortment of organic substances originate from secondary metabolism that are produced by relatively small building blocks such as acetyl coenzyme A, shikimic acid, mevalonic acid, methylerythritol phosphate, and aminoacids. The great majority of these compounds do not appear to participate directly in growth and the development of organism production. Accordingly, they are not necessarily produced under all conditions, and in the most cases the function of these compounds and their benefits is not yet known.

Several secondary metabolites mediate relationships between organisms such us virulence factors, attractants for other useful organisms, defence factors, etc. Moreover, often their distribution is cross-special, as observed, for example, in plants and their endophytes. Finally, secondary metabolites show interesting action mechanisms and peculiar chemical properties. 

The principal goal of this Special Issue is to cover all aspects of chemical and biotechnological relevance, such us extraction, identification, structural and stereostructural elucidation, biological activities, the rules of biotic and abiotic factors on secondary metabolites expressions and the development of analytical methods for their detection, and other related researches.  

Thus, this Special Issue aims at collecting contributions from the field and providing a platform to make them more visible to the scientific community.

Dr. Anna Andolfi
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Structure and stereostructure elucidation
  • Analytical techniques
  • Optimization of growth conditions
  • Dual culture method
  • Biological activities
  • Structure–activity relationship
  • Biotic and abiotic factors on secondary metabolite production
  • Chemical properties

Published Papers (10 papers)

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Research

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Open AccessArticle
Ginkgo biloba Extract Protects against Methotrexate-Induced Hepatotoxicity: A Computational and Pharmacological Approach
Molecules 2020, 25(11), 2540; https://doi.org/10.3390/molecules25112540 - 29 May 2020
Abstract
Ginkgo biloba extract possess several promising biological activities; currently, it is clinically employed in the management of several diseases. This research work aimed to extrapolate the antioxidant and anti-inflammatory effects of Ginkgo biloba (Gb) in methotrexate (MTX)-induced liver toxicity model. These effects were [...] Read more.
Ginkgo biloba extract possess several promising biological activities; currently, it is clinically employed in the management of several diseases. This research work aimed to extrapolate the antioxidant and anti-inflammatory effects of Ginkgo biloba (Gb) in methotrexate (MTX)-induced liver toxicity model. These effects were analyzed using different in vivo experimental approaches and by bioinformatics analysis. Male SD rats were grouped as follows: saline; MTX; Gb (pretreated for seven days with 60, 120, and 180 mg/kg daily dose before MTX treatment); silymarin (followed by MTX treatment); Gb 180 mg/kg daily only; and silymarin only. Histopathological results revealed that MTX induced marked hepatic injury, associated with a substantial surge in various hepatic enzymes such as alanine transaminase (ALT), aspartate transaminase (AST), and serum alkaline phosphatase (ALP). Furthermore, MTX caused the triggering of oxidative distress associated with a depressed antioxidant system. All these injury markers contributed to a significant release of apoptotic (caspase-3 and c-Jun N-terminal kinases (JNK)) and tumor necrosis factor (TNF-α)-like inflammatory mediators. Treatment with Gb counteracts MTX-mediated apoptosis and inflammation dose-dependently along with modulating the innate antioxidative mechanisms such as glutathione (GSH) and glutathione S-transferase (GST). These results were further supplemented by in silico study to analyze drug-receptor interactions (for several Gb constituents and target proteins) stabilized by a low energy value and with a good number of hydrogen bonds. These findings demonstrated that Gb could ameliorate MTX-induced elevated liver reactive oxygen species (ROS) and inflammation, possibly by JNK and TNF-α modulation. Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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Open AccessArticle
Cornus macrophylla, the Antibacterial Activity of Organic Leaf Extracts and the Characterization of the More Lipophilic Components by GC/MS
Molecules 2020, 25(10), 2395; https://doi.org/10.3390/molecules25102395 - 21 May 2020
Abstract
In the present study, the antibacterial activity of Cornus macrophylla was examined. Organic solvent extracts of leaves were prepared using methanol, n-hexane, chloroform, and ethyl acetate. Antibacterial activity was examined by using a 100 mg/mL extract concentration. Penicillin was kept as a [...] Read more.
In the present study, the antibacterial activity of Cornus macrophylla was examined. Organic solvent extracts of leaves were prepared using methanol, n-hexane, chloroform, and ethyl acetate. Antibacterial activity was examined by using a 100 mg/mL extract concentration. Penicillin was kept as a positive control while dimethyl sulfoxide was taken as a negative control. Methanolic extract exhibited a 21.5, 36.3, 25.3, and 23.7 mm inhibition zone diameter (IZD); n-hexane showed a 33, 40, 32.8, and 28.7 mm IZD; chloroform showed a 18.8, 29, 22.3, and 21.6 mm IZD; and ethyl acetate showed a 23.5, 30.2, 30, and 22.3 mm IZD against Erwinia carotovora, Pseudomonas syringae, Ralstonia solanacearum, and Xanthomonas axonopodis, respectively. The n-hexane extract revealed high antibacterial activity against all bacterial species as compared with methanolic, chloroform, and ethyl acetate extract. Gas Chromatography Mass Spectrometry (GC/MS) analysis of n-hexane extract depicted the presence of 55 compounds. Out of these compounds, one compound, identified as α-amyrin (Mol. wt = 426), exhibited the maximum peak area (32.64%), followed by A’-Neogammacer-22(29)-en-3-ol, acetate, (3.beta.,21.beta.)- (Mol. wt = 468) and β-amyrin (Mol. wt = 426) having peak areas of 25.97 and 6.77%, respectively. It was concluded that the antibacterial activity observed during the present investigation may be due to these compounds. Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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Open AccessFeature PaperArticle
Bivalent Metal-Chelating Properties of Harzianic Acid Produced by Trichoderma pleuroticola Associated to the Gastropod Melarhaphe neritoides
Molecules 2020, 25(9), 2147; https://doi.org/10.3390/molecules25092147 - 04 May 2020
Cited by 1
Abstract
Harzianic acid is a secondary metabolite of Trichoderma, structurally belonging to the dienyltetramic acid subgroup of the tetramic acids. Biological activities of harzianic acid are of great interest for its antimicrobial and plant growth-promoting activities, which might be related to its chelating [...] Read more.
Harzianic acid is a secondary metabolite of Trichoderma, structurally belonging to the dienyltetramic acid subgroup of the tetramic acids. Biological activities of harzianic acid are of great interest for its antimicrobial and plant growth-promoting activities, which might be related to its chelating properties. In the present work harzianic acid, isolated from cultures of a strain of Trichoderma pleuroticola associated to the gastropod Melarhaphe neritoides, was studied as a complexant agent of a number of biologically relevant transition metals (i.e., Zn2+, Fe2+, Cu2+, and Mn2+), using UV-VIS, potentiometry, MS and NMR techniques. Our findings show the coordination capacity of harzianic acid toward the above cations through the formation of neutral or charged complexes in a variable ratio depending on the metal and pH conditions. Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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Open AccessFeature PaperArticle
Phenolic Compounds of Soybean Seeds from Two European Countries and Their Antioxidant Properties
Molecules 2020, 25(9), 2075; https://doi.org/10.3390/molecules25092075 - 29 Apr 2020
Abstract
There is only a small acreage of planted soybeans in northern Europe, as the global production of this crop is mainly dictated by the warmer temperatures needed for bountiful yields. The defense response of soybean plants to a cold climate entails the secretion [...] Read more.
There is only a small acreage of planted soybeans in northern Europe, as the global production of this crop is mainly dictated by the warmer temperatures needed for bountiful yields. The defense response of soybean plants to a cold climate entails the secretion of specific compounds which help mitigate oxidative stress, i.e., antioxidants, including phenolic compounds. The objective of this study was to examine differences in the concentrations of phenolic compounds, their antioxidant properties, and the concentration of key isoflavones (namely genistein, daidzein, malonyl daidzein, malonyl genistein, and daidzin) in the seeds of six soybean cultivars from two different regions of Europe, namely Poland and France. The total phenolic contents, isoflavone levels, and in vitro antioxidant capacities of soybean seeds from most of the investigated cultivars of northeast Europe were found to be greater than those from southwest Europe. The phenolic compounds of seed extracts are primarily responsible for the free-radical scavenging of soybeans. Factors regulating the production of phenolic compounds in the seeds have not been thoroughly elucidated. Hence, the results presented in this paper can be useful in the selection of soybean cultivars with higher levels of seed phenolics, because of their beneficial impact on human health and on the soybean’s defense mechanism against plant stresses. Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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Open AccessArticle
Gentiana lutea Extract Modulates Ceramide Synthesis in Primary and Psoriasis-Like Keratinocytes
Molecules 2020, 25(8), 1832; https://doi.org/10.3390/molecules25081832 - 16 Apr 2020
Abstract
Gentiana lutea is a bitter herb that is traditionally used to improve gastric disorders. Recently, we have shown that Gentiana lutea extract (GE) also modulates the lipid metabolism of human keratinocytes in vitro and in vivo. In the present study, we investigated the [...] Read more.
Gentiana lutea is a bitter herb that is traditionally used to improve gastric disorders. Recently, we have shown that Gentiana lutea extract (GE) also modulates the lipid metabolism of human keratinocytes in vitro and in vivo. In the present study, we investigated the role of GE on ceramide synthesis in human primary keratinocytes (HPKs) and psoriasis-like keratinocytes. We could demonstrate that GE increased the concentrations of glucosylceramides and the ceramide AS/AdS subclass without affecting the overall ceramide content in HPKs. The expression of ceramide synthase 3 (CERS3) and elongases (ELOVL1 and 4) was reduced in psoriasis lesions compared to healthy skin. Psoriasis-like HPKs, generated by stimulating HPKs with cytokines that are involved in the pathogenesis of psoriasis (IL-17, TNF-α, IL-22 and IFN-γ) showed increased levels of IL-6, IL-8 and increased expression of DEFB4A, as well as decreased expression of ELOVL4. The treatment with GE partly rescued the reduced expression of ELOVL4 in psoriasis-like HPKs and augmented CERS3 expression. This study has shown that GE modulates ceramide synthesis in keratinocytes. Therefore, GE might be a novel topical treatment for skin diseases with an altered lipid composition such as psoriasis. Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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Open AccessArticle
Hepatoprotective Effects of Standardized Extracts from an Ancient Italian Apple Variety (Mela Rosa dei Monti Sibillini) against Carbon Tetrachloride (CCl4)-Induced Hepatotoxicity in Rats
Molecules 2020, 25(8), 1816; https://doi.org/10.3390/molecules25081816 - 15 Apr 2020
Cited by 1
Abstract
The aim of this research was to examine the effect of the hydroalcoholic extracts from the peel (APE) and pulp (APP) of a traditional apple cultivar from central Italy (Mela Rosa dei Monti Sibillini) on CCl4-induced hepatotoxicity in rats. Phytoconstituents were [...] Read more.
The aim of this research was to examine the effect of the hydroalcoholic extracts from the peel (APE) and pulp (APP) of a traditional apple cultivar from central Italy (Mela Rosa dei Monti Sibillini) on CCl4-induced hepatotoxicity in rats. Phytoconstituents were determined by liquid chromatography–mass spectrometry (LC-MS) analysis showing an abundance of proanthocyanidins and flavonol derivatives together with the presence of annurcoic acid in APE. Wistar rats received APE/APP (30 mg/kg oral administration) for three days before CCl4 injection (2 mL/kg intraperitoneal once on the third day). Treatment with both APE and APP prior to CCl4 injection significantly decreased the serum levels of aspartate aminotransferase (AST), alkaline phosphatase (ALP) and alanine aminotransferase (ALT) compared to the CCl4 group. Besides, pretreatment with APE reversed the CCl4 effects on superoxide dismutase (SOD), myeloperoxidase (MPO), tumor necrosis factor-α (TNF-α) and interleukin-1beta (IL-1β) levels in liver tissue in rats and reduced tissue damage as shown in hematoxylin and eosin staining. These results showed that this ancient Italian apple is worthy of use in nutraceuticals and dietary supplements to prevent and/or protect against liver disorders. Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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Open AccessArticle
Euryops pectinatus L. Flower Extract Inhibits P-glycoprotein and Reverses Multi-Drug Resistance in Cancer Cells: A Mechanistic Study
Molecules 2020, 25(3), 647; https://doi.org/10.3390/molecules25030647 - 03 Feb 2020
Cited by 1
Abstract
Euryops pectinatus is a South African ornamental plant belonging to family Asteraceae. The present work evaluates the cytotoxic activity and phytochemical profile of the flower extract. Metabolite profiling was performed using HPLC-PDA-ESI-MS/MS. Total phenolics and flavonoids content were assessed. Cytotoxicity was evaluated against [...] Read more.
Euryops pectinatus is a South African ornamental plant belonging to family Asteraceae. The present work evaluates the cytotoxic activity and phytochemical profile of the flower extract. Metabolite profiling was performed using HPLC-PDA-ESI-MS/MS. Total phenolics and flavonoids content were assessed. Cytotoxicity was evaluated against 6 different cancer cell lines using MTT assay. The possible underlying mechanism was proposed. We analyzed whether the extract could overcome the resistance of multidrug-resistant cancer cells for doxorubicin. The effect of combination of E. pectinatus with doxorubicin was also studied. Additionally, the potential inhibitory activity of the identified phytochemicals to PB1 protein was analyzed using in silico molecular docking. Twenty-five compounds were tentatively identified. Total phenolic and flavonoid contents represented 49.41 ± 0.66 and 23.37 ± 0.23 µg/mg dried flower extract, respectively. The extract showed selective cytotoxicity against Caco2 cells but its main effect goes beyond mere cytotoxicity. It showed strong inhibition of P-glycoprotein, which helps to overcome multidrug resistance to classical chemotherapeutic agents. In silico molecular docking showed that dicaffeoyl quinic acid, kaempferol-O-rutinoside, rutin, and isorhamnetin-O-rutinoside exhibited the most potent inhibitory activity to PB1 involved in tumor progression. Euryops pectinatus flower heads could have promising selective cytotoxicity alone or in combination with other chemotherapeutic agents to counteract multidrug resistance. Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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Open AccessArticle
A Widely Metabolomic Analysis Revealed Metabolic Alterations of Epimedium Pubescens Leaves at Different Growth Stages
Molecules 2020, 25(1), 137; https://doi.org/10.3390/molecules25010137 - 29 Dec 2019
Abstract
Epimedium folium is the major medicinally-used organ of Epimedium species and its metabolic changes during the leaf growth have not been studied at the metabolomic level. E. pubescens is one of five recorded species in the Pharmacopoeia of the People’s Republic of China [...] Read more.
Epimedium folium is the major medicinally-used organ of Epimedium species and its metabolic changes during the leaf growth have not been studied at the metabolomic level. E. pubescens is one of five recorded species in the Pharmacopoeia of the People’s Republic of China and widely grows in China. A UPLC-ESI-MS/MS-based targeted metabolomic analysis was implemented to explore the metabolite composition in E. pubescens leaves under the cultivation condition and further to investigate their temporal variations among four representative growth stages. A total of 403 metabolites, including 32 hitherto known in Epimedium species, were identified in E. pubescens leaf, of which 302 metabolites showed the growth/development-dependent alterations. Flavonoid-type compounds were the major composition of the metabolites identified in this study. Most flavonoids, together with tannin-type and lignans and coumarin-type compounds, were up-regulated with E. pubescens leaf growth and maturation after the full flowering stage. Our results not only greatly enriched the existing Epimedium phytochemical composition database and also, for the first time, provided the metabolomics-wide information on metabolic changes during E. pubescens leaf growth and development, which would facilitate in the choice of an optimum harvest time to balance a higher biomass yield of Epimedium folium with its better medicinal quality. Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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Review

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Open AccessReview
Bioactive Phytochemical Constituents of Wild Edible Mushrooms from Southeast Asia
Molecules 2020, 25(8), 1972; https://doi.org/10.3390/molecules25081972 - 23 Apr 2020
Cited by 1
Abstract
Mushrooms have a long history of uses for their medicinal and nutritional properties. They have been consumed by people for thousands of years. Edible mushrooms are collected in the wild or cultivated worldwide. Recently, mushroom extracts and their secondary metabolites have acquired considerable [...] Read more.
Mushrooms have a long history of uses for their medicinal and nutritional properties. They have been consumed by people for thousands of years. Edible mushrooms are collected in the wild or cultivated worldwide. Recently, mushroom extracts and their secondary metabolites have acquired considerable attention due to their biological effects, which include antioxidant, antimicrobial, anti-cancer, anti-inflammatory, anti-obesity, and immunomodulatory activities. Thus, in addition to phytochemists, nutritionists and consumers are now deeply interested in the phytochemical constituents of mushrooms, which provide beneficial effects to humans in terms of health promotion and reduction of disease-related risks. In recent years, scientific reports on the nutritional, phytochemical and pharmacological properties of mushroom have been overwhelming. However, the bioactive compounds and biological properties of wild edible mushrooms growing in Southeast Asian countries have been rarely described. In this review, the bioactive compounds isolated from 25 selected wild edible mushrooms growing in Southeast Asia have been reviewed, together with their biological activities. Phytoconstituents with antioxidant and antimicrobial activities have been highlighted. Several evidences indicate that mushrooms are good sources for natural antioxidants and antimicrobial agents Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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Open AccessReview
Halogenated Metabolites from the Diet of Aplysia dactylomela Rang
Molecules 2020, 25(4), 815; https://doi.org/10.3390/molecules25040815 - 13 Feb 2020
Abstract
Invertebrates are an important source of structurally-diverse and biologically-active halogenated metabolites. The sea hare Aplysia dactylomela Rang has long been known to possess halogenated metabolites of dietary origin that are used as a self-defense mechanism. The compounds from Aplysia dactylomela Rang are comprised [...] Read more.
Invertebrates are an important source of structurally-diverse and biologically-active halogenated metabolites. The sea hare Aplysia dactylomela Rang has long been known to possess halogenated metabolites of dietary origin that are used as a self-defense mechanism. The compounds from Aplysia dactylomela Rang are comprised mainly of terpenoids and small percentages of C-15 acetogenins, indoles, macrolides, sterols and alkaloids with potent cytotoxic, anti-microbial and anti-inflammatory properties. For decades the metabolites discovered have been investigated for their medical and pharmaceutical applications, so much so that the ecological role of the metabolites has been overlooked. The interaction between Aplysia dactylomela Rang and its diet that is comprised of seaweed can provide information into the distribution and diversity of the seaweed, the application of bioaccumulated secondary metabolites as part of its defense mechanism and the potential roles of these metabolites for adaptation in the marine environment. This paper compiles the diversity of halogenated secondary metabolites documented from Aplysia dactylomela Rang. Full article
(This article belongs to the Special Issue Natural Secondary Metabolites)
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