Anti-Vibrio Indole-Diterpenoids and C-25 Epimeric Steroids From the Marine-Derived Fungus Penicillium janthinellum

Persteroid, a new steroid from the marine-derived fungus Penicillium sp. ZYX-Z-143

A new steroid named persteroid (1) and seven known compounds (2-8) were isolated from the marine-derived fungus Penicillium sp. ZYX-Z-143. The structure of 1 was determined by HRESIMS, NMR, and ECD calculations. Compound 1 showed inhibitory activity against protein tyrosine phosphatase 1B (PTP1B) with IC50 value of 46.31 ± 0.52 μM. Moreover, compound 1 potently suppressed nitric oxide (NO) production on lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. The cytotoxicity and antibacterial activity of all isolates were tested.

Ergone Derivatives from the Deep-Sea-Derived Fungus Aspergillus terreus YPGA10 and 25,28-Dihydroxyergone-Induced Apoptosis in Human Colon Cancer SW620 Cells

Ten new ergone derivatives (1-10) and five known analogues (11-15) were isolated from the deep-sea-derived fungus Aspergillus terreus YPGA10. The structures including the absolute configurations were established by detailed analysis of the NMR spectroscopic data, HRESIMS, ECD calculation, and coupling constant calculation. All the structures are characterized by a highly conjugated 25-hydroxyergosta-4,6,8(14),22-tetraen-3-one nucleus. Structurally, compound 2 bearing a 15-carbonyl group and compounds 5-7 possessing a 15β-OH/OCH3 group are rarely encountered in ergone derivatives. Bioassay results showed that compounds 1 and 11 demonstrated cytotoxic effects on human colon cancer SW620 cells with IC50 values of 8.4 and 3.1 μM, respectively. Notably, both compounds exhibited negligible cytotoxicity on the human normal lung epithelial cell BEAS-2B. Compound 11 was selected for preliminary mechanistic study and was found to inhibit cell proliferation and induce apoptosis in human colon cancer SW620 cells. In addition, compound 1 displayed cytotoxic activity against five human leukemia cell lines with IC50 values ranging from 5.7 to 8.9 μM. Our study demonstrated that compound 11 may serve as a potential candidate for the development of anticolorectal cancer agents.

Structural diversity and biological activities of indole-diterpenoids from Penicillium janthinellum by co-culture with Paecilomyces formosus

Co-culturing the marine-derived fungi Penicillium janthinellium with Paecilomyces formosus led to the isolation of nine new indole-diterpenes, janthinellumines A-I (1-9), along with twelve known analogues (10-21). The chemical structures including their absolute configurations of them were assigned by the analysis of extensive spectroscopic data and calculated ECD and VCD methods. These indole-diterpenoids displayed extensive biological activities, including anti-influenza A virus, protein tyrosine phosphatase (PTP) inhibitory, and anti-Vibrio activities. Among them, the anti-influenza mechanism of compounds 1, 2, and 7 was further investigated using neuraminidase inhibitory assay, molecular docking, and reverse genetics methods, suggesting that 1, 2, and 7 could interact with Arg371 of the viral neuraminidase. The structure-activity relationship (SAR) of PTPs inhibitory activity for indole-diterpene derivatives (1, 2, 4, 5, 9-16, and 19-21) was also summarized.

Talasteroid, a new withanolide from the marine-derived fungus Talaromyces stollii

A new withanolide, talasteroid (1), and a known steroid (2), along with eight meroterpenoids (3-10), were obtained from the rice culture of the marine-derived fungus Talaromyces stollii HBU-115. The structure of 1 including its absolute configuration was determined by extensive 1 D and 2 D NMR spectroscopy, and single-crystal X-ray diffraction analysis. Compound 1 represents the first withanolide featuring a 4-substituted 2,3-dimethyl-2-butenolide ring in the side chain. The isolated compounds were evaluated for their antimicrobial and antioxidant activities.

Bioactive and unusual steroids from Penicillium fungi

Penicillium fungi are represented by various species and can be found worldwide and thrive in a range of environments, such as in the soil, air, and indoors, and in marine environments, as well as food products. Chemical investigation of species of this genus has led to the discovery of compounds from several structural classes with varied bioactivities. As an example, this genus has been a source of bioactive and structurally unusual steroids. The scope of this short review is to cover specialized metabolites of the steroid class and the cytotoxic, antimicrobial, anti-inflammatory as well as phytotoxic activities of these compounds. Other steroids that possess unusual structures, with significant bioactivity yet to determined, will also be discussed to further demonstrate the structural diversity of this compound class from Penicillium fungi, and hopefully inspire the further exploration of such compounds to uncover their activity.

Anti-Vibrio potential of natural products from marine microorganisms

The emergence of drug-resistant Vibrio poses a serious threat to aquaculture and human health, thus there is an urgent need for the discovery of new related antibiotics. Given that marine microorganisms (MMs) are evidenced as important sources of antibacterial natural products (NPs), great attention has been gained to the exploration of potential anti-Vibrio agents from MMs. This review summarizes the occurrence, structural diversity, and biological activities of 214 anti-Vibrio NPs isolated from MMs (from 1999 to July 2022), including 108 new compounds. They were predominantly originated from marine fungi (63%) and bacteria (30%) with great structural diversity, including polyketides, nitrogenous compounds, terpenoids, and steroids, among which polyketides account for nearly half (51%) of them. This review will shed light on the development of MMs derived NPs as potential anti-Vibrio lead compounds with promising applications in agriculture and human health.

Anti-IAV indole-diterpenoids from the marine-derived fungus Penicillium citrinum

A new indole-diterpenoid, penijanthine E (1), and a known analogue (2), were obtained from the PDB culture of the marine-derived fungus Penicillium citrinum ZSS-9. The absolute configuration of 1 was elucidated by calculated TDDFT ECD and DP4plus calculations. The absolute configuration of 2 was confirmed by single-crystal X-ray diffraction analysis and TDDFT ECD calculations. Compounds 1 and 2 showed antiviral activity against influenza A virus (IAV) of A/WSN/33(H1N1) and A/PR/8/34(H1N1) strains with IC₅₀ values ranging from 12.6 to 46.8 μM.

Natural products as antivibrio agents: insight into the chemistry and biological activity

Vibriosis causes serious problems and economic loss in aquaculture and human health. Investigating natural products as antivibrio agents has gained more attention to combat vibriosis. The present review highlights the chemical diversity of antivibrio isolated from bacteria, fungi, plants, and marine organisms. Based on the study covering the literature from 1985-2021, the chemical diversity ranges from alkaloids, terpenoids, polyketides, sterols, and peptides. The mechanisms of action are included inhibiting growth, interfering with biofilm formation, and disrupting of quorum sensing. Relevant summaries focusing on the source organisms and the associated bioactivity of different chemical classes are also provided. Further research on in vivo studies, toxicity, and clinical is required for the application in aquaculture and human health.

The Biosynthesis Related Enzyme, Structure Diversity and Bioactivity Abundance of Indole-Diterpenes: A Review

Indole diterpenes are a large class of secondary metabolites produced by fungi, possessing a cyclic diterpenoid backbone and an indole moiety. Novel structures and important biological activity have made indole diterpenes one of the focuses of synthetic chemists. Although the discovery, identification, structural diversity, biological activity and especially structure-activity relationship of indole diterpenes have been reported in some papers in recent years, they are absent of a systematic and comprehensive analysis, and there is no elucidation of enzymes related to this kind of natural product. Therefore, it is necessary to summarize the relevant reports to provide new perspectives for the following research. In this review, for the first time, the function of related synthases and the structure-activity relationship of indole diterpenes are expounded, and the recent research advances of them are emphasized.

Thiazolo[5,4-b]pyridine Alkaloid and Seven ar-Bisabol Sesquiterpenes Produced by the Endophytic Fungus Penicillium janthinellum

We investigated the secondary metabolites present in Penicillium janthinellum MPT-25, an endophytic fungus isolated from Taxus wallichiana var. chinensis (Pilger) Florin. Chemical characterization of the solid cultured extract resulted in the isolation of 11 compounds, including eight previously undescribed metabolites: a thiazolo[5,4-b]pyridine alkaloid, janthinedine A (1), and seven ar-bisabol sesquiterpenes, janthinepenes A-G (2-8). Their structures were elucidated by a combination of extensive spectroscopic methods, including single-crystal X-ray diffraction and ECD spectra. The antimicrobial activities of these compounds were evaluated against seven agricultural pathogenic fungi and eight clinically drug-resistant bacteria.

Anti-inflammatory Polyketides from the Marine-Derived Fungus Eutypella scoparia

Three new polyketides, eutyketides A and B (1 and 2) and cytosporin X (3), along with four known compounds (4-7), were obtained from the marine-derived fungus Eutypella scoparia. The planar structures of 1 and 2 were elucidated by extensive HRMS and 1D and 2D NMR analyses. Their relative configurations of C-13 and C-14 were determined with chemical conversions by introducing an acetonylidene group. The absolute configurations of 1-3 were determined by comparing their experimental electronic circular dichroism (ECD) data with their computed ECD results. All of the isolated compounds were tested for their anti-inflammatory activities on lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophages. Compounds 5 and 6 showed stronger anti-inflammatory activities than the other compounds, with the inhibition of 49.0% and 54.9% at a concentration of 50.0 µg/mL, respectively.

Oxalierpenes A and B, Unusual Indole-Diterpenoid Derivatives with Antiviral Activity from a Marine-Derived Strain of the Fungus Penicillium oxalicum

Oxalierpenes A and B (1 and 2), two unusual indole-diterpenoid derivatives, were obtained from the marine-derived fungus Penicillium oxalicum. The absolute configurations of 1 and 2 were elucidated by calculated TDDFT ECD and DP4plus methods. Oxalierpene A (1) represents the first indole-diterpenoid derivative with a five-membered ring of 4-hydroxy-5,5-dimethyldihydrofuran-3-one as a side chain. Oxalierpene B (2) has a unique 6/5/6/5/5/6/6/5/5 ring system. Compounds 1 and 2 showed antiviral activity against the H1N1 virus and respiratory syncytial virus (RSV), with IC₅₀ values ranging from 2.8 to 9.4 μM.

Marine fungal metabolites as a source of drug leads against aquatic pathogens

Aquatic pathogens, including Vibrio, Edwardsiella, Pseudomonas, and Aeromonas, which could result in bacterial diseases to aquaculture, have seriously threatened the world aquaculture production. Marine-derived fungi, which could produce novel secondary metabolites with significant antibacterial activity, may be an important source for finding effective agents against aquatic pathogens. In this review, a systematically overview of the harm of several aquatic pathogens, and 134 antibacterial secondary metabolites against aquatic pathogens from 13 genera of marine-derived fungi, were summarized and concluded. The aim of this review is to find out the relationships between activity and structural type, between bioactive compounds and their hosts, and so on. Altogether, 95 references published during 1997-2021 were cited. KEY POINTS: •Aquatic pathogens, which could result in bacterial diseases to aquaculture, were described. •Marine fungal metabolites with activities against aquatic pathogens were summarized. •The distributions of these bioactive marine fungal metabolites were analyzed.

Antimicrobial Diterpenes: Recent Development From Natural Sources

Antimicrobial resistance has been posing an alarming threat to the treatment of infectious diseases over the years. Ineffectiveness of the currently available synthetic and semisynthetic antibiotics has led the researchers to discover new molecules with potent antimicrobial activities. To overcome the emerging antimicrobial resistance, new antimicrobial compounds from natural sources might be appropriate. Secondary metabolites from natural sources could be prospective candidates in the development of new antimicrobial agents with high efficacy and less side effects. Among the natural secondary metabolites, diterpenoids are of crucial importance because of their broad spectrum of antimicrobial activity, which has put it in the center of research interest in recent years. The present work is aimed at reviewing recent literature regarding different classes of natural diterpenes and diterpenoids with significant antibacterial, antifungal, antiviral, and antiprotozoal activities along with their reported structure-activity relationships. This review has been carried out with a focus on relevant literature published in the last 5 years following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 229 diterpenoids from various sources like plants, marine species, and fungi are summarized in this systematic review, including their chemical structures, classification, and significant antimicrobial activities together with their reported mechanism of action and structure-activity relationships. The outcomes herein would provide researchers with new insights to find new credible leads and to work on their synthetic and semisynthetic derivatives to develop new antimicrobial agents.

Natural Indole Alkaloids from Marine Fungi: Chemical Diversity and Biological Activities

The indole scaffold is one of the most important heterocyclic ring systems for pharmaceutical development, and serves as an active moiety in several clinical drugs. Fungi derived from marine origin are more liable to produce novel indole-containing natural products due to their extreme living environments. The indole alkaloids from marine fungi have drawn considerable attention for their unique chemical structures and significant biological activities. This review attempts to provide a summary of the structural diversity of marine fungal indole alkaloids including prenylated indoles, diketopiperazine indoles, bisindoles or trisindoles, quinazoline-containing indoles, indole-diterpenoids, and other indoles, as well as their known biological activities, mainly focusing on cytotoxic, kinase inhibitory, antiinflammatory, antimicrobial, anti-insecticidal, and brine shrimp lethal effects. A total of 306 indole alkaloids from marine fungi have been summarized, covering the references published from 1995 to early 2021, expecting to be beneficial for drug discovery in the future.

Marine Indole Alkaloids-Isolation, Structure and Bioactivities

Indole alkaloids are heterocyclic natural products with extensive pharmacological activities. As an important source of lead compounds, many clinical drugs have been derived from natural indole compounds. Marine indole alkaloids, from unique marine environments with high pressure, high salt and low temperature, exhibit structural diversity with various bioactivities, which attracts the attention of drug researchers. This article is a continuation of the previous two comprehensive reviews and covers the literature on marine indole alkaloids published from 2015 to 2021, with 472 new or structure-revised compounds categorized by sources into marine microorganisms, invertebrates, and plant-derived. The structures and bioactivities demonstrated in this article will benefit the synthesis and pharmacological activity study for marine indole alkaloids on their way to clinical drugs.

Anti-Vibrio dibutyl phthalate from marine-derived Streptomyces sp. S073

Marine Streptomyces S073 was previously shown to have strong anti-Vibrio activity, and its antibacterial mechanism was proposed to be associated with siderophore-mediated iron competition and other antagonistic agents. In this study, anti-Vibrio compounds produced by S073 were isolated by bioassay-guided fractionation using column chromatography and HPLC, and the target compound in the most active fraction was identified as dibutyl phthalate (DBP) by various spectroscopic analyses, including EI-MS, ¹H NMR and ¹³C NMR. The DBP-producing capacity of S073 was 2.39 mg/L in ISP1 culture media. Pure DBP was demonstrated to have strong inhibitory activity on Vibiro parahaemolyticus growth with an MIC of 31.25 mg/L. When standard DBP was supplemented into the S073 fermentation broth in a gradient method, an additive inhibitory effect on V. parahaemolyticus was observed, indicating the important role of DBP in driving anti-Vibrio activity in S073 metabolites pool. A synergistic additive effect between DBP and florfenicol was observed in the Vibrio inhibition. These results indicate that, to achieve Vibrio-inhibition, S073 exerted multifaceted strategies, which included DBP-mediated antagonism and siderophore-governed iron competition. The application potential of S073 as an aquaculture probiotic was evaluated, and the safety risks associated with the endocrine disruptor attributes of DBP were discussed.

The chemistry and biology of fungal meroterpenoids (2009-2019)

Fungal meroterpenoids are secondary metabolites from mixed terpene-biosynthetic origins. Their intriguing chemical structural diversification and complexity, potential bioactivities, and pharmacological significance make them attractive targets in natural product chemistry, organic synthesis, and biosynthesis. This review provides a systematic overview of the isolation, chemical structural features, biological activities, and fungal biodiversity of 1585 novel meroterpenoids from 79 genera terrestrial and marine-derived fungi including macrofungi, Basidiomycetes, in 441 research papers in 2009-2019. Based on the nonterpenoid starting moiety in their biosynthesis pathway, meroterpenoids were classified into four categories (polyketide-terpenoid, indole-, shikimate-, and miscellaneous-) with polyketide-terpenoids (mainly tetraketide-) and shikimate-terpenoids as the primary source. Basidiomycota produced 37.5% of meroterpenoids, mostly shikimate-terpenoids. The genera of Ganoderma, Penicillium, Aspergillus, and Stachybotrys are the four dominant producers. Moreover, about 56% of meroterpenoids display various pronounced bioactivities, including cytotoxicity, enzyme inhibition, antibacterial, anti-inflammatory, antiviral, antifungal activities. It's exciting that several meroterpenoids including antroquinonol and 4-acetyl antroquinonol B were developed into phase II clinically used drugs. We assume that the chemical diversity and therapeutic potential of these fungal meroterpenoids will provide biologists and medicinal chemists with a large promising sustainable treasure-trove for drug discovery.

A critical review on the use of DP4+ in the structural elucidation of natural products: the good, the bad and the ugly. A practical guide

Covering: 2015 up to the end of 2020Even in the golden age of NMR, the number of natural products being incorrectly assigned is becoming larger every day. The use of quantum NMR calculations coupled with sophisticated data analysis provides ideal complementary tools to facilitate the elucidation process in challenging cases. Among the current computational methodologies to perform this task, the DP4+ probability is a popular and widely used method. This updated version of Goodman's DP4 synergistically combines NMR calculations at higher levels of theory with the Bayesian analysis of both scaled and unscaled data. Since its publication in late 2015, the use of DP4+ to solve controversial natural products has substantially grown, with several predictions being confirmed by total synthesis. To date, the structures of more than 200 natural products were determined with the aid of DP4+. However, all that glitters is not gold. Besides its intrinsic limitations, on many occasions it has been improperly used with potentially important consequences on the quality of the assignment. Herein we present a critical revision on how the scientific community has been using DP4+, exploring the strengths of the method and how to obtain optimal results from it. We also analyze the weaknesses of DP4+, and the paths to by-pass them to maximize the confidence in the structural elucidation.

Arthriniumsteroids A-D, four new steroids from the soft coral-derived fungus Simplicillium lanosoniveum SCSIO41212

Four new steroids derivatives, namely arthriniumsteroids A - D (1-4), together with two known compounds, were isolated from the soft coral-derived fungus Simplicillium lanosoniveum SCSIO41212. Their structures were elucidated by spectroscopic analysis and by comparison with those reported in the literature. The absolute configuration of 2 was confirmed by single-crystal X-ray diffraction. In bioassay, all compounds showed weak inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 cells.

Metabolites of Marine Sediment-Derived Fungi: Actual Trends of Biological Activity Studies

Marine sediments are characterized by intense degradation of sedimenting organic matter in the water column and near surface sediments, combined with characteristically low temperatures and elevated pressures. Fungi are less represented in the microbial communities of sediments than bacteria and archaea and their relationships are competitive. This results in wide variety of secondary metabolites produced by marine sediment-derived fungi both for environmental adaptation and for interspecies interactions. Earlier marine fungal metabolites were investigated mainly for their antibacterial and antifungal activities, but now also as anticancer and cytoprotective drug candidates. This review aims to describe low-molecular-weight secondary metabolites of marine sediment-derived fungi in the context of their biological activity and covers research articles published between January 2016 and November 2020.

Marine-derived fungi as a source of bioactive indole alkaloids with diversified structures

Marine-derived fungi are well known as rich sources of bioactive natural products. Growing evidences indicated that indole alkaloids, isolated from a variety of marine-derived fungi, have attracted considerable attention for their diverse, challenging structural complexity and promising bioactivities, and therefore, indole alkaloids have potential to be pharmaceutical lead compounds. Systemic compilation of the relevant literature. In this review, we demonstrated a comprehensive overview of 431 new indole alkaloids from 21 genera of marine-derived fungi with an emphasis on their structures and bioactivities, covering literatures published during 1982-2019.

Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) 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 (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.

Meroterpenoids produced by fungi: Occurrence, structural diversity, biological activities, and their molecular targets

Meroterpenoids are partially derived from the terpenoids, distributing widely in the plants, animals and fungi. The complex structures and diverse bioactivities of meroterpenoids have attracted more attention for chemists and pharmacologists. Since the first review summarized by Geris in 2009, there are absent of systematic reviews reported about meroterpenoids from the higher and lower fungi up to now. In the past decades, myriads of meroterpenoids were discovered, and it is necessary to summarize these meroterpenoids about their unique structures and promising bioactivities. In this review, we use a new classification method based on the non-terpene precursors, and also highlight the structural features, bioactivity of natural meroterpenoids from the higher and lower fungi covering the period of September 2008 to February 2020. A total of 709 compounds were discussed and cited the 182 references. Meanwhile, we also primarily summarize their occurrence, structural diversity, biological activities, and molecular targets.

A Review of Terpenes from Marine-Derived Fungi: 2015-2019

Marine-derived fungi are a significant source of pharmacologically active metabolites with interesting structural properties, especially terpenoids with biological and chemical diversity. In the past five years, there has been a tremendous increase in the rate of new terpenoids from marine-derived fungi being discovered. In this updated review, we examine the chemical structures and bioactive properties of new terpenes from marine-derived fungi, and the biodiversity of these fungi from 2015 to 2019. A total of 140 research papers describing 471 new terpenoids of six groups (monoterpenes, sesquiterpenes, diterpenes, sesterterpenes, triterpenes, and meroterpenes) from 133 marine fungal strains belonging to 34 genera were included. Among them, sesquiterpenes, meroterpenes, and diterpenes comprise the largest proportions of terpenes, and the fungi genera of Penicillium, Aspergillus, and Trichoderma are the dominant producers of terpenoids. The majority of the marine-derived fungi are isolated from live marine matter: marine animals and aquatic plants (including mangrove plants and algae). Moreover, many terpenoids display various bioactivities, including cytotoxicity, antibacterial activity, lethal toxicity, anti-inflammatory activity, enzyme inhibitor activity, etc. In our opinion, the chemical diversity and biological activities of these novel terpenoids will provide medical and chemical researchers with a plenty variety of promising lead compounds for the development of marine drugs.

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.

Chemical Diversity and Biological Activities of Meroterpenoids from Marine Derived-Fungi: A Comprehensive Update

Meroterpenoids are a class of hybrid natural products, partially derived from a mixed terpenoid pathway. They possess remarkable structural features and relevant biological and pharmacological activities. Marine-derived fungi are a rich source of meroterpenoids featuring structural diversity varying from simple to complex molecular architectures. A combination of a structural variability and their myriad of bioactivities makes meroterpenoids an interesting class of naturally occurring compounds for chemical and pharmacological investigation. In this review, a comprehensive literature survey covering the period of 2009–2019, with 86 references, is presented focusing on chemistry and biological activities of various classes of meroterpenoids isolated from fungi obtained from different marine hosts and environments.

Piperazine ring formation by a single-module NRPS and cleavage by an α-KG-dependent nonheme iron dioxygenase in brasiliamide biosynthesis

Brasiliamides are a class of piperazine-containing alkaloids produced by Penicillium brasilianum with a range of pharmaceutical activities. The mechanism of brasiliamide biosynthesis, including piperazine ring formation and multiple tailoring modifications, still remains unclear. In this study, the biosynthetic gene cluster of brasiliamides, brs, was identified from the marine-derived fungal strain Penicillium brasilianum WZXY-M122-9. Deletion of a histone deacetylase-encoding gene using a CRISPR/Cas9 gene editing system led to the production of a new compound, namely brasiliamide I (1). The brs-encoded single-module nonribosomal peptide synthetase (NRPS) BrsA is involved in the formation of the piperazine skeleton of brasiliamides. Full-length BrsA protein (113.6 kDa) was purified, and reconstitution of enzymatic activity in vitro confirmed that BrsA stereoselectively accepts L-phenylalanine as the substrate. Multiple deletion of tailoring genes and analysis of purified proteins in vitro enabled us to propose a brasiliamide biosynthetic pathway. In the tailoring steps, an α-ketoglutarate (KG)-dependent nonheme iron dioxygenase, BrsJ, was identified to catalyze piperazine ring cleavage during biosynthesis of brasiliamide A (2). KEY POINTS: The gene cluster encoding brasiliamide biosynthesis, brs, is identified. Deletion of a histone deacetylase-encoding gene produces brasiliamide I. BrsA catalyzes brasiliamide piperazine skeleton formation. BrsJ catalyzes piperazine ring cleavage to produce brasiliamide A. Graphical abstract.

One new α,β-unsaturated 7-ketone sterol from the mangrove-derived fungus Phomopsis sp.MGF222

A new α,β-unsaturated 7-ketone sterol, 5β,6β-epoxy-3β, 15α-dihydroxy-(22E,24R)-ergosta-8(14),22-dien-7-one (1), along with five known sterone derivatives, 5β,6β-epoxy-3β,7α-dihydroxy-(22E,24R)-ergosta-8(14),22-dien-15-one (2), 5β,6β-epoxy-3β,7α,9α-trihydroxy-(22E,24R)-ergosta-8(14),22-dien-15-one (3), 3β,9α,15α-trihydroxy-(22E,24R)-10(5→4)-abeo-ergosta-6,8(14),22-trien-5-one (4), 3,15-dihydroxyl-(22E,24R)-ergosta-5,8(14),22-trien-7-one (5) and (22E,24R)-ergosta-4,6,8(14),22-tetraen-3,15-dione (6) were isolated from the mangrove-derived fungus Phomopsis sp. MGF222. Their structures were established on the basis of extensive spectroscopic data and comparison with the data of literature. Compound 2 showed weak antibacterial activity against Micrococcus tenuis with the MIC value of 28.2 (±0.52) μM. Compound 5 exhibited moderate antibacterial activity against Staphylococcus aureus with the MIC value of 14.6 (±0.47) μM.

Asperienes A-D, Bioactive Sesquiterpenes from the Marine-Derived Fungus Aspergillus flavus

Marine-derived fungi of the genera Aspergillus could produce novel compounds with significant bioactivities. Among these fungi, the strain Aspergillus flavus is notorious for its mutagenic mycotoxins production. However, some minor components with certain toxicities from A. flavus have not been specifically surveyed and might have potent biological activities. Our investigation of the marine-derived fungus Aspergillus flavus CF13-11 cultured in solid medium led to the isolation of four C-6′/C-7′ epimeric drimane sesquiterpene esters, asperienes A–D (1–4). Their absolute configurations were assigned by electronic circular dichroism (ECD) and Snatzke’s methods. This is the first time that two pairs of C-6′/C-7′ epimeric drimane sesquiterpene esters have successfully been separated. Aperienes A–D (1–4) displayed potent bioactivities towards four cell lines with the IC₅₀ values ranging from 1.4 to 8.3 μM. Interestingly, compounds 1 and 4 exhibited lower toxicities than 2 and 3 toward normal GES-1 cells, indicating more potential for development as an antitumor agent in the future.