Activated production of silent metabolites from marine-derived fungus Penicillium citrinum

OSMAC Strategy: A promising way to explore microbial cyclic peptides

Microbial secondary metabolites are pivotal for the development of novel drugs. However, conventional culture techniques, have left a vast array of unexpressed biosynthetic gene clusters (BGCs) in microorganisms, hindering the discovery of metabolites with distinct structural features and diverse biological functions. To address this limitation, several innovative strategies have been emerged. The "One Strain Many Compounds" (OSMAC) strategy, which involves altering microbial culture conditions, has proven to be particularly effective in mining numerous novel secondary metabolites for the past few years. Among these, microbial cyclic peptides stand out. These peptides often comprise rare amino acids, unique chemical structures, and remarkable biological function. With the advancement of the OSMAC strategy, a plethora of new cyclic peptides have been identified from diverse microbial genera. This work reviews the progress in mining novel compounds using the OSMAC strategy and the applications of this strategy in discovering 284 microbial cyclic peptides from 63 endophytic strains, aiming to offer insights for the further explorations into novel active cyclic peptides.

Isolation and insecticidal activities of new cyclic peptides from mangrove endophytic fungus Aspergillus sp. GXNU-4QQY1a

An investigation on bioactive metabolites from the mangrove endophytic fungus Aspergillus sp. GXNU-4QQY1a led to the isolation of two undescribed cyclic peptides, guaspertide A (1) and guaspertide B (2), together with six known compounds, 3-8. These structures and the new compounds' absolute configuration were determined by mass spectrometry analysis, nuclear magnetic resonance spectrum, electronic circular dichroism, and single-crystal X-ray diffraction. Insecticidal assays were carried out with compounds 1-8, and the results showed that compounds 1-3 and 8 exhibited good insecticidal activity against citrus psyllids.

A new cytotoxic phenalenone derivative from Penicillium oxalicum

From the supernatant of the fermentation broth of Penicillium oxalicum, we isolated a previously undescribed peniciphenalenin G (1) and three known compounds 2-4. Their chemical structures were established through spectroscopic analysis as well as comparing with data in the literature. Compound 1 displayed a moderate cytotoxicity with IC₅₀ value 21.4 μM (positive drug regorafenib with IC₅₀ value of 8.2 μM) against Caco2 cells while compounds 2 and 3 showed weak cytotoxicities with IC₅₀ value of 52.1 and 39.2 μM, respectively.

How to Completely Squeeze a Fungus-Advanced Genome Mining Tools for Novel Bioactive Substances

Fungal species have the capability of producing an overwhelming diversity of bioactive substances that can have beneficial but also detrimental effects on human health. These so-called secondary metabolites naturally serve as antimicrobial "weapon systems", signaling molecules or developmental effectors for fungi and hence are produced only under very specific environmental conditions or stages in their life cycle. However, as these complex conditions are difficult or even impossible to mimic in laboratory settings, only a small fraction of the true chemical diversity of fungi is known so far. This also implies that a large space for potentially new pharmaceuticals remains unexplored. We here present an overview on current developments in advanced methods that can be used to explore this chemical space. We focus on genetic and genomic methods, how to detect genes that harbor the blueprints for the production of these compounds (i.e., biosynthetic gene clusters, BGCs), and ways to activate these silent chromosomal regions. We provide an in-depth view of the chromatin-level regulation of BGCs and of the potential to use the CRISPR/Cas technology as an activation tool.

Antimicrobial and Antioxidant Metabolites From the Cultured Suspension Cells of Marchantia polymorpha L

Cell suspension culture is an attractive alternative source to wild plant for the production of novel biological metabolites. Hence, in this study, chemical investigation of cell suspension cultivated Marchantia polymorpha L. was performed, and led to the isolation of one new bis-bibenzyl (1), along with nine known analogues (2-10). Those chemical structures were elucidated based on the comprehensive analysis of NMR and MS data. The antioxidant and antibacterial effects of isolated components and crude extracts were evaluated, resulting in the identification of some antioxidant and antibacterial components. Meanwhile, Compare to that of wild grown M. polymorpha, the cell cultivated one was found to produce superior phenol yields, these constituents are of great importance for their antioxidant and antimicrobial activities. The studies conducted so far have established that the cell culture of M. polymorpha can be considered not only as a rich source of phenolic but as promising source of natural antioxidants and antibiotics as well, which is also expected to develop for better usage of this medicinal herb.

Scandium-microorganism interactions in new biotechnologies

Scandium (Sc) plays a special role in high-tech industries because of its wide application in green, space, and defense technologies. However, Sc mining and purification are problematic due to political, technological, and environmental difficulties. The deficit of this element limits global technological development. One sustainable solution to this problem is to use microorganisms to extract Sc from ore and waste, as well as to concentrate and separate it from other elements. Sc also demonstrates attractive metabolic effects on microbes that is of great interest in white biotechnology. Sc increases the production of proteins and secondary metabolites and activates poorly expressed genes. This review offers a comprehensive analysis of current knowledge on the application of Sc-microorganism interactions in promising biotechnologies, its perspectives, and future challenges.

Cryptic Metabolites from Marine-Derived Microorganisms Using OSMAC and Epigenetic Approaches

Marine microorganisms have proven to be a source of new natural products with a wide spectrum of biological activities relevant in different industrial sectors. The ever-increasing number of sequenced microbial genomes has highlighted a discrepancy between the number of gene clusters potentially encoding the production of natural products and the actual number of chemically characterized metabolites for a given microorganism. Homologous and heterologous expression of these biosynthetic genes, which are often silent under experimental laboratory culture conditions, may lead to the discovery of new cryptic natural products of medical and biotechnological interest. Several new genetic and cultivation-based strategies have been developed to meet this challenge. The OSMAC approach (one strain-many compounds), based on modification of growth conditions, has proven to be a powerful strategy for the discovery of new cryptic natural products. As a direct extension of this approach, the addition of chemical elicitors or epigenetic modifiers have also been used to activate silent genes. This review looks at the structures and biological activities of new cryptic metabolites from marine-derived microorganisms obtained using the OSMAC approach, the addition of chemical elicitors, and enzymatic inhibitors and epigenetic modifiers. It covers works published up to June 2021.

Comprehensive Overview on the Chemistry and Biological Activities of Selected Alkaloid Producing Marine-Derived Fungi as a Valuable Reservoir of Drug Entities

Marine-associated fungal strains act as a valuable reservoir of bioactive diverse secondary metabolites including alkaloids which are highly popular by their biological activities. This review highlighted the chemistry and biology of alkaloids isolated from twenty-six fungal genera associated with marine organisms and marine sea sediments. The selected fungi are from different marine sources without focusing on mangroves. The studied fungal genera comprises Acrostalagmus, Arthrinium, Chaetomium, Cladosporium, Coniothyrium, Curvularia, Dichotomomyces, Eurotium, Eutypella, Exophiala, Fusarium, Hypocrea, Microsphaeropsis, Microsporum, Neosartorya, Nigrospora, Paecilomyces, Penicillium, Pleosporales, Pseudallescheria, Scedosporium, Scopulariopsis, Stagonosporopsis, Thielavia, Westerdykella, and Xylariaceae. Around 347 alkaloid metabolites were isolated and identified via chromatographic and spectroscopic techniques comprising 1D and 2D NMR (one and two dimensional nuclear magnetic resonance) which were further confirmed using HR-MS (high resolution mass spectrometry) and Mosher reactions for additional ascertaining of the stereochemistry. About 150 alkaloids showed considerable effect with respect to the tested activities. Most of the reported bioactive alkaloids showed considerable biological activities mainly cytotoxic followed by antibacterial, antifungal, antiviral, antioxidant; however, a few showed anti-inflammatory and antifouling activities. However, the rest of the compounds showed weak or no activity toward the tested biological activities and required further investigations for additional biological activities. Thus, alkaloids isolated from marine-associated fungi can afford an endless source of new drug entities that could serve as leads for drug discovery combating many human ailments.

Marine natural products

This review covers the literature published between January and December in 2018 for marine natural products (MNPs), with 717 citations (706 for the period January to December 2018) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1554 in 469 papers for 2018), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. The proportion of MNPs assigned absolute configuration over the last decade is also surveyed.

Alkaloids from Marine Fungi: Promising Antimicrobials

Resistance of pathogenic microorganisms against antimicrobials is a major threat to contemporary human society. It necessitates a perpetual influx of novel antimicrobial compounds. More specifically, Gram⁻ pathogens emerged as the most exigent danger. In our continuing quest to search for novel antimicrobial molecules, alkaloids from marine fungi show great promise. However, current reports of such newly discovered alkaloids are often limited to cytotoxicity studies and, moreover, neglect to discuss the enigma of their biosynthesis. Yet, the latter is often a prerequisite to make them available through sufficiently efficient processes. This review aims to summarize novel alkaloids with promising antimicrobial properties discovered in the past five years and produced by marine fungi. Several discovery strategies are summarized, and knowledge gaps in biochemical production routes are identified. Finally, links between the structure of the newly discovered molecules and their activity are proposed. Since 2015, a total of 35 new antimicrobial alkaloids from marine fungi were identified, of which 22 showed an antibacterial activity against Gram⁻ microorganisms. Eight of them can be classified as narrow-spectrum Gram⁻ antibiotics. Despite this promising ratio of novel alkaloids active against Gram⁻ microorganisms, the number of newly discovered antimicrobial alkaloids is low, due to the narrow spectrum of discovery protocols that are used and the fact that antimicrobial properties of newly discovered alkaloids are barely characterized. Alternatives are proposed in this review. In conclusion, this review summarizes novel findings on antimicrobial alkaloids from marine fungi, shows their potential as promising therapeutic candidates, and hints on how to further improve this potential.

Newly reported alkaloids produced by marine-derived Penicillium species (covering 2014-2018)

Alkaloids, especially heterocyclic alkaloids, have received remarkable attention due to their intriguing structures and potential pharmacological activities. The marine fungi residing in extreme environmental conditions are among the richest sources of these basic nitrogen-containing compounds. Fungal species belonging to the genus Penicillium have been studied worldwide for their biosynthetic potential for generating bioactive alkaloids. This paper offers a systematic review of the newly reported alkaloids produced by marine-derived Penicillium species over the past five years (covering the literature from the beginning of 2014 through the end of 2018) and describes the structural diversity, biological activities, and plausible biosynthetic pathway of the reported compounds. A total of 106 alkaloids and 81 references are included in this review, which is expected to be beneficial for drug development and biosynthesis in the near future.