Special Issue "Bioactive Natural Products from the Red Sea"

A special issue of Marine Drugs (ISSN 1660-3397).

Deadline for manuscript submissions: closed (31 March 2021) | Viewed by 28414

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Special Issue Editors

Prof. Dr. Mostafa Rateb
E-Mail Website
Guest Editor
School of Computing, Engineering, & Physical Sciences, University of the West of Scotland, Paisley PA1 2BE, UK
Interests: bioactive microbial natural products; marine bacteria; marine endophytes; structure elucidation
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Usama Ramadan Abdelmohsen
E-Mail Website
Guest Editor
Head of Pharmacognosy Department, Faculty of Pharmacy, Deraya University, Minia, Egypt
Interests: natural products; metabolomics; marine microbiology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,                

The marine environment has proven to be a very rich source of diverse natural products with relevant activities such as anticancer, anti-inflammatory, antiepileptic, immunomodulatory, antifungal, antiviral, and antiparasitic. The global marine pharmaceutical clinical pipeline comprises 30 compounds originating from different marine invertebrates and marine microorganisms, which includes eight approved drugs by the most representative approving agencies and 22 drug candidates in phase III, II, or I of drug development clinical phases. Marine invertebrates and associated microorganisms are capable of synthesizing diverse classes of secondary metabolites and, in some cases, novel chemical leads that have never been discovered by terrestrial counterparts.   

The Red Sea is the world’s northernmost tropical sea which acts as an inlet of the Indian Ocean, lying between Africa and Asia. It has a surface area of roughly 450,000 km2 and is about 2250 km long, with a maximum depth of around 3000 m. Salinity-wise, the Red Sea is approximately 5% greater than the world average due to high rate of evaporation and lack of significant rivers or streams draining into it. The Red Sea is a rich and diverse ecosystem due to the 2000 km of coral reef extending along its coastline. It is inhabited by over 1000 invertebrate species, and 200 soft and hard corals. Due to this high biodiversity and limited research, the Red Sea is a promising underexplored habitat for the discovery of new bioactive marine natural products.

This Special Issue “Bioactive Natural Products from the Red Sea” in Marine Drugs will cover the scope of isolation and structure characterization of natural products derived from invertebrates and microorganisms collected from the Red Sea. Phylogenetic and diversity studies as well as new methodologies for isolating marine microorganisms will also be targeted in this Special Issue.

As Guest Editors, we encourage all researchers who are interested in Red Sea marine research to contribute their latest research findings in this area. We hope that this issue will help us all to gain more knowledge about marine organisms and microbes as leading sources for drug discovery in such an underexplored habitat.

Dr. Mostafa Rateb
Prof. Dr. Usama Ramadan Abdelmohsen
Guest Editors

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 submissions that pass pre-check are 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. Marine Drugs is an international peer-reviewed open access monthly 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 2400 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

  • Marine invertebrates
  • Marine microbes
  • Drug discovery
  • Bioactive natural products
  • Structure elucidation

Published Papers (10 papers)

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Editorial

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Editorial
Bioactive Natural Products from the Red Sea
Mar. Drugs 2021, 19(6), 289; https://doi.org/10.3390/md19060289 - 21 May 2021
Cited by 1 | Viewed by 1406
Abstract
The marine environment has proven to be a rich source of diverse natural products with relevant activities such as anticancer, anti-inflammatory, antiepileptic, immunomodulatory, antifungal, antiviral, and antiparasitic [...] Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)

Research

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Article
Antimicrobial and Antibiofilm Activities of the Fungal Metabolites Isolated from the Marine Endophytes Epicoccum nigrum M13 and Alternaria alternata 13A
Mar. Drugs 2021, 19(4), 232; https://doi.org/10.3390/md19040232 - 20 Apr 2021
Cited by 16 | Viewed by 2675
Abstract
Epicotripeptin (1), a new cyclic tripeptide along with four known cyclic dipeptides (25) and one acetamide derivative (6) were isolated from seagrass-associated endophytic fungus Epicoccum nigrum M13 recovered from the Red Sea. Additionally, two new [...] Read more.
Epicotripeptin (1), a new cyclic tripeptide along with four known cyclic dipeptides (25) and one acetamide derivative (6) were isolated from seagrass-associated endophytic fungus Epicoccum nigrum M13 recovered from the Red Sea. Additionally, two new compounds, cyclodidepsipeptide phragamide A (7) and trioxobutanamide derivative phragamide B (8), together with eight known compounds (916), were isolated from plant-derived endophyte Alternaria alternata 13A collected from a saline lake of Wadi El Natrun depression in the Sahara Desert. The structures of the isolated compounds were determined based on the 1D and 2D NMR spectroscopic data, HRESIMS data, and a comparison with the reported literature. The absolute configurations of 1 and 7 were established by advanced Marfey’s and Mosher’s ester analyses. The antimicrobial screening indicated that seven of the tested compounds exhibited considerable (MIC range of 2.5–5 µg/mL) to moderate (10–20 µg/mL) antibacterial effect against the tested Gram-positive strains and moderate to weak (10–30 µg/mL) antibacterial effect against Gram-negative strains. Most of the compounds exhibited weak or no activity against the tested Gram-negative strains. On the other hand, four of the tested compounds showed considerable antibiofilm effects against biofilm forming Gram-positive and Gram-negative strains. Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)
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Article
Bio-Guided Isolation of Antimalarial Metabolites from the Coculture of Two Red Sea Sponge-Derived Actinokineospora and Rhodococcus spp.
Mar. Drugs 2021, 19(2), 109; https://doi.org/10.3390/md19020109 - 12 Feb 2021
Cited by 7 | Viewed by 2581
Abstract
Coculture is a productive technique to trigger microbes’ biosynthetic capacity by mimicking the natural habitats’ features principally by competition for food and space and interspecies cross-talks. Mixed cultivation of two Red Sea-derived actinobacteria, Actinokineospora spheciospongiae strain EG49 and Rhodococcus sp. UR59, resulted in [...] Read more.
Coculture is a productive technique to trigger microbes’ biosynthetic capacity by mimicking the natural habitats’ features principally by competition for food and space and interspecies cross-talks. Mixed cultivation of two Red Sea-derived actinobacteria, Actinokineospora spheciospongiae strain EG49 and Rhodococcus sp. UR59, resulted in the induction of several non-traced metabolites in their axenic cultures, which were detected using LC–HRMS metabolomics analysis. Antimalarial guided isolation of the cocultured fermentation led to the isolation of the angucyclines actinosporins E (1), H (2), G (3), tetragulol (5) and the anthraquinone capillasterquinone B (6), which were not reported under axenic conditions. Interestingly, actinosporins were previously induced when the axenic culture of the Actinokineospora spheciospongiae strain EG49 was treated with signalling molecule N-acetyl-d-glucosamine (GluNAc); this finding confirmed the effectiveness of coculture in the discovery of microbial metabolites yet to be discovered in the axenic fermentation with the potential that could be comparable to adding chemical signalling molecules in the fermentation flask. The isolated angucycline and anthraquinone compounds exhibited in vitro antimalarial activity and good biding affinity against lysyl-tRNA synthetase (PfKRS1), highlighting their potential developability as new antimalarial structural motif. Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)
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Article
Bioactive Steroids from the Red Sea Soft Coral Sinularia polydactyla
Mar. Drugs 2020, 18(12), 632; https://doi.org/10.3390/md18120632 - 10 Dec 2020
Cited by 11 | Viewed by 2227
Abstract
Six new (1, 2, 6, 8, 13, and 20) and twenty previously isolated (35, 7, 912, 1419, and 2126) steroids featuring thirteen different [...] Read more.
Six new (1, 2, 6, 8, 13, and 20) and twenty previously isolated (35, 7, 912, 1419, and 2126) steroids featuring thirteen different carbocycle motifs were isolated from the organic extract of the soft coral Sinularia polydactyla collected from the Hurghada reef in the Red Sea. The structures and the relative configurations of the isolated natural products have been determined based on extensive analysis of their NMR and MS data. The cytotoxic, anti-inflammatory, anti-angiogenic, and neuroprotective activity of compounds 37, 912, 1420, and 2226, as well as their effect on androgen receptor-regulated transcription was evaluated in vitro in human tumor and non-cancerous cells. Steroids 22 and 23 showed significant cytotoxicity in the low micromolar range against the HeLa and MCF7 cancer cell lines, while migration of endothelial cells was inhibited by compounds 11, 12, 22, and 23 at 20 µM. The results of the androgen receptor (AR) reporter assay showed that compound 11 exhibited the strongest inhibition of AR at 10 µM, while it is noteworthy that steroids 10, 16, and 20 displayed increased inhibition of AR with decreasing concentrations. Additionally, compounds 11 and 23 showed neuroprotective activity on neuron-like SH-SY5Y cells. Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)
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Article
Antimicrobial Chlorinated 3-Phenylpropanoic Acid Derivatives from the Red Sea Marine Actinomycete Streptomyces coelicolor LY001
Mar. Drugs 2020, 18(9), 450; https://doi.org/10.3390/md18090450 - 27 Aug 2020
Cited by 16 | Viewed by 2796
Abstract
The actinomycete strain Streptomyces coelicolor LY001 was purified from the sponge Callyspongia siphonella. Fractionation of the antimicrobial extract of the culture of the actinomycete afforded three new natural chlorinated derivatives of 3-phenylpropanoic acid, 3-(3,5-dichloro-4-hydroxyphenyl)propanoic acid (1), 3-(3,5-dichloro-4-hydroxyphenyl)propanoic acid methyl ester [...] Read more.
The actinomycete strain Streptomyces coelicolor LY001 was purified from the sponge Callyspongia siphonella. Fractionation of the antimicrobial extract of the culture of the actinomycete afforded three new natural chlorinated derivatives of 3-phenylpropanoic acid, 3-(3,5-dichloro-4-hydroxyphenyl)propanoic acid (1), 3-(3,5-dichloro-4-hydroxyphenyl)propanoic acid methyl ester (2), and 3-(3-chloro-4-hydroxyphenyl)propanoic acid (3), together with 3-phenylpropanoic acid (4), E-cinnamic acid (5), and the diketopiperazine alkaloids cyclo(l-Phe-trans-4-OH-l-Pro) (6) and cyclo(l-Phe-cis-4-OH-d-Pro) (7) were isolated. Interpretation of nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HRESIMS) data of 17 supported their assignments. Compounds 13 are first candidates of the natural chlorinated phenylpropanoic acid derivatives. The production of the chlorinated derivatives of 3-phenylpropionic acid (13) by S. coelicolor provides insight into the biosynthetic capabilities of the marine-derived actinomycetes. Compounds 13 demonstrated significant and selective activities towards Escherichia. coli and Staphylococcus aureus, while Candida albicans displayed more sensitivity towards compounds 6 and 7, suggesting a selectivity effect of these compounds against C. albicans. Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)
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Article
Thalassosterol, a New Cytotoxic Aromatase Inhibitor Ergosterol Derivative from the Red Sea Seagrass Thalassodendron ciliatum
Mar. Drugs 2020, 18(7), 354; https://doi.org/10.3390/md18070354 - 08 Jul 2020
Cited by 16 | Viewed by 2486
Abstract
Thalassodendron ciliatum (Forssk.) Den Hartog is a seagrass belonging to the plant family Cymodoceaceae with ubiquitous phytoconstituents and important pharmacological potential, including antioxidant, antiviral, and cytotoxic activities. In this work, a new ergosterol derivative named thalassosterol (1) was isolated from the [...] Read more.
Thalassodendron ciliatum (Forssk.) Den Hartog is a seagrass belonging to the plant family Cymodoceaceae with ubiquitous phytoconstituents and important pharmacological potential, including antioxidant, antiviral, and cytotoxic activities. In this work, a new ergosterol derivative named thalassosterol (1) was isolated from the methanolic extract of T. ciliatum growing in the Red Sea, along with two known first-reported sterols, namely ergosterol (2) and stigmasterol (3), using different chromatographic techniques. The structure of the new compound was established based on 1D and 2D NMR spectroscopy and high-resolution mass spectrometry (HR-MS) and by comparison with the literature data. The new ergosterol derivative showed significant in vitro antiproliferative potential against the human cervical cancer cell line (HeLa) and human breast cancer (MCF-7) cell lines, with IC50 values of 8.12 and 14.24 µM, respectively. In addition, docking studies on the new sterol 1 explained the possible binding interactions with an aromatase enzyme; this inhibition is beneficial in both cervical and breast cancer therapy. A metabolic analysis of the crude extract of T. ciliatum using liquid chromatography combined with high-resolution electrospray ionization mass spectrometry (LC-ESI-HR-MS) revealed the presence of an array of phenolic compounds, sterols and ceramides, as well as di- and triglycerides. Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)
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Article
Induction of Antibacterial Metabolites by Co-Cultivation of Two Red-Sea-Sponge-Associated Actinomycetes Micromonospora sp. UR56 and Actinokinespora sp. EG49
Mar. Drugs 2020, 18(5), 243; https://doi.org/10.3390/md18050243 - 05 May 2020
Cited by 19 | Viewed by 3098
Abstract
Liquid chromatography coupled with high resolution mass spectrometry (LC-HRESMS)-assisted metabolomic profiling of two sponge-associated actinomycetes, Micromonospora sp. UR56 and Actinokineospora sp. EG49, revealed that the co-culture of these two actinomycetes induced the accumulation of metabolites that were not traced in their axenic cultures. [...] Read more.
Liquid chromatography coupled with high resolution mass spectrometry (LC-HRESMS)-assisted metabolomic profiling of two sponge-associated actinomycetes, Micromonospora sp. UR56 and Actinokineospora sp. EG49, revealed that the co-culture of these two actinomycetes induced the accumulation of metabolites that were not traced in their axenic cultures. Dereplication suggested that phenazine-derived compounds were the main induced metabolites. Hence, following large-scale co-fermentation, the major induced metabolites were isolated and structurally characterized as the already known dimethyl phenazine-1,6-dicarboxylate (1), phenazine-1,6-dicarboxylic acid mono methyl ester (phencomycin; 2), phenazine-1-carboxylic acid (tubermycin; 3), N-(2-hydroxyphenyl)-acetamide (9), and p-anisamide (10). Subsequently, the antibacterial, antibiofilm, and cytotoxic properties of these metabolites (13, 9, and 10) were determined in vitro. All the tested compounds except 9 showed high to moderate antibacterial and antibiofilm activities, whereas their cytotoxic effects were modest. Testing against Staphylococcus DNA gyrase-B and pyruvate kinase as possible molecular targets together with binding mode studies showed that compounds 13 could exert their bacterial inhibitory activities through the inhibition of both enzymes. Moreover, their structural differences, particularly the substitution at C-1 and C-6, played a crucial role in the determination of their inhibitory spectra and potency. In conclusion, the present study highlighted that microbial co-cultivation is an efficient tool for the discovery of new antimicrobial candidates and indicated phenazines as potential lead compounds for further development as antibiotic scaffold. Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)
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Article
New Cytotoxic Natural Products from the Red Sea Sponge Stylissa carteri
Mar. Drugs 2020, 18(5), 241; https://doi.org/10.3390/md18050241 - 03 May 2020
Cited by 8 | Viewed by 3187
Abstract
Bioactivity-guided isolation supported by LC-HRESIMS metabolic profiling led to the isolation of two new compounds, a ceramide, stylissamide A (1), and a cerebroside, stylissoside A (2), from the methanol extract of the Red Sea sponge Stylissa carteri. Structure [...] Read more.
Bioactivity-guided isolation supported by LC-HRESIMS metabolic profiling led to the isolation of two new compounds, a ceramide, stylissamide A (1), and a cerebroside, stylissoside A (2), from the methanol extract of the Red Sea sponge Stylissa carteri. Structure elucidation was achieved using spectroscopic techniques, including 1D and 2D NMR and HRMS. The bioactive extract’s metabolomic profiling showed the existence of various secondary metabolites, mainly oleanane-type saponins, phenolic diterpenes, and lupane triterpenes. The in vitro cytotoxic activity of the isolated compounds was tested against two human cancer cell lines, MCF-7 and HepG2. Both compounds, 1 and 2, displayed strong cytotoxicity against the MCF-7 cell line, with IC50 values at 21.1 ± 0.17 µM and 27.5 ± 0.18 µM, respectively. They likewise showed a promising activity against HepG2 with IC50 at 36.8 ± 0.16 µM for 1 and IC50 30.5 ± 0.23 µM for 2 compared to the standard drug cisplatin. Molecular docking experiments showed that 1 and 2 displayed high affinity to the SET protein and to inhibitor 2 of protein phosphatase 2A (I2PP2A), which could be a possible mechanism for their cytotoxic activity. This paper spreads light on the role of these metabolites in holding fouling organisms away from the outer surface of the sponge, and the potential use of these defensive molecules in the production of novel anticancer agents. Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)
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Article
Azaphilones from the Red Sea Fungus Aspergillus falconensis
Mar. Drugs 2020, 18(4), 204; https://doi.org/10.3390/md18040204 - 10 Apr 2020
Cited by 17 | Viewed by 2509
Abstract
The marine-derived fungus Aspergillus falconensis, isolated from sediment collected from the Canyon at Dahab, Red Sea, yielded two new chlorinated azaphilones, falconensins O and P (1 and 2) in addition to four known azaphilone derivatives (36) [...] Read more.
The marine-derived fungus Aspergillus falconensis, isolated from sediment collected from the Canyon at Dahab, Red Sea, yielded two new chlorinated azaphilones, falconensins O and P (1 and 2) in addition to four known azaphilone derivatives (36) following fermentation of the fungus on solid rice medium containing 3.5% NaCl. Replacing NaCl with 3.5% NaBr induced accumulation of three additional new azaphilones, falconensins Q−S (79) including two brominated derivatives (7 and 8) together with three known analogues (1012). The structures of the new compounds were elucidated by 1D and 2D NMR spectroscopy and HRESIMS data as well as by comparison with the literature. The absolute configuration of the azaphilone derivatives was established based on single-crystal X-ray diffraction analysis of 5, comparison of NMR data and optical rotations as well as on biogenetic considerations. Compounds 1, 39, and 11 showed NF-κB inhibitory activity against the triple negative breast cancer cell line MDA-MB-231 with IC50 values ranging from 11.9 to 72.0 µM. Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)
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Review

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Review
Natural Products Repertoire of the Red Sea
Mar. Drugs 2020, 18(9), 457; https://doi.org/10.3390/md18090457 - 04 Sep 2020
Cited by 14 | Viewed by 4485
Abstract
Marine natural products have achieved great success as an important source of new lead compounds for drug discovery. The Red Sea provides enormous diversity on the biological scale in all domains of life including micro- and macro-organisms. In this review, which covers the [...] Read more.
Marine natural products have achieved great success as an important source of new lead compounds for drug discovery. The Red Sea provides enormous diversity on the biological scale in all domains of life including micro- and macro-organisms. In this review, which covers the literature to the end of 2019, we summarize the diversity of bioactive secondary metabolites derived from Red Sea micro- and macro-organisms, and discuss their biological potential whenever applicable. Moreover, the diversity of the Red Sea organisms is highlighted as well as their genomic potential. This review is a comprehensive study that compares the natural products recovered from the Red Sea in terms of ecological role and pharmacological activities. Full article
(This article belongs to the Special Issue Bioactive Natural Products from the Red Sea)
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