3-Carboxy-indole derivatives from the deep-sea-derived fungus Phomopsis tersa FS441

Three new compounds phomtersines A-C (1-3) together with nine known compounds were isolated from the marine-derived fungus Phomopsis tersa FS441. Their structures were sufficiently established by spectroscopic methods, including extensive 1D and 2D NMR techniques and modified Snatzke's method. Moreover, compounds 1-12 were evaluated for cytotoxic and anti-inflammatory activities. As a result, phomtersine B (2) and the known compound 10 showed moderate cytotoxic activity against the four tested cell lines with IC50 values ranging from 20.21 to 36.53 μM, and phomtersine A (1) exhibited moderate inhibitory activity against LPS-induced NO production.

Screening of marine sediment-derived microorganisms and their bioactive metabolites: a review

Marine sediments are one of the largest habitats on Earth, and their unique ecology, such as high salinity, high pressure, and hypoxia, may activate certain silent genes in marine microbes, resulting in microbes, enzymes, active products, and specific metabolic pathways that can adapt to these specific ecological environments. Marine sediment-derived microorganisms and their bioactive metabolites are of great significance and have potential commercial development prospects for food, pharmaceutical, chemical industries, agriculture, environmental protection and human nutrition and health. In recent years, although there have been numerous scientific reports surrounding marine sediment-derived microorganisms and their bioactive metabolites, a comprehensive review of their research progress is lacking. This paper presents the development and renewal of traditional culture-dependent and omics analysis techniques and their application to the screening of marine sediment-derived microorganisms producing bioactive substances. It also highlights recent research advances in the last five years surrounding the types, functional properties and potential applications of bioactive metabolites produced by marine sediment-derived microorganisms. These bioactive metabolites mainly include antibiotics, enzymes, enzyme inhibitors, sugars, proteins, peptides, and some other small molecule metabolites. In addition, the review ends with concluding remarks on the challenges and future directions for marine sediment-derived microorganisms and their bioactive metabolites. The review report not only helps to deepen the understanding of marine sediment-derived microorganisms and their bioactive metabolites, but also provides some useful information for the exploitation and utilization of marine microbial resources and the mining of new compounds with potential functional properties.

Biological activities of meroterpenoids isolated from different sources

Meroterpenoids are natural products synthesized by unicellular organisms such as bacteria and multicellular organisms such as fungi, plants, and animals, including those of marine origin. Structurally, these compounds exhibit a wide diversity depending upon the origin and the biosynthetic pathway they emerge from. This diversity in structural features imparts a wide spectrum of biological activity to meroterpenoids. Based on the biosynthetic pathway of origin, these compounds are either polyketide-terpenoids or non-polyketide terpenoids. The recent surge of interest in meroterpenoids has led to a systematic screening of these compounds for many biological actions. Different meroterpenoids have been recorded for a broad range of operations, such as anti-cholinesterase, COX-2 inhibitory, anti-leishmanial, anti-diabetic, anti-oxidative, anti-inflammatory, anti-neoplastic, anti-bacterial, antimalarial, anti-viral, anti-obesity, and insecticidal activity. Meroterpenoids also possess inhibitory activity against the expression of nitric oxide, TNF- α, and other inflammatory mediators. These compounds also show renal protective, cardioprotective, and neuroprotective activities. The present review includes literature from 1999 to date and discusses 590 biologically active meroterpenoids, of which 231 are from fungal sources, 212 are from various species of plants, and 147 are from marine sources such as algae and sponges.

Stereochemical and Biosynthetic Rationalisation of the Tropolone Sesquiterpenoids

This review summarises the known structures, biological activities, and biosynthetic pathways of the tropolone sesquiterpenoid family of fungal secondary metabolites. Synthesis of this knowledge allows likely structural and stereochemical misassignments to be revised and shows how the compounds can be divided into three main biosynthetic classes based on the stereochemistry of key biosynthetic steps.

Neocucurbols A-H, Phomactin Diterpene Derivatives from the Marine-Derived Fungus Neocucurbitaria unguis-hominis FS685

Neocucurbols A-D (1-4) are diterpene derivatives that possess a complex 6/6/5/5/6 polycyclic ring system with a characteristic tetrahedrofuran bridge ring skeleton. Neocucurbols E-H (5-8) are diterpenes that feature a 6/8/6 tricyclic ring system. Their structures were unambiguously determined by detailed spectroscopic analyses, X-ray diffractions studies, and ECD calculations. All compounds (1-8) were evaluated for in vitro antimicrobial and cytotoxic activities.

Novel geranylhydroquinone derived meroterpenoids from the fungus Clitocybe clavipes and their cytotoxic activity

Three novel geranylhydroquinone derived meroterpenoids, named clavilactones J and K (1-2) and clavipol C (3), were isolated from the basidiomycete Clitocybe clavipes. Their structures were unambiguously identified by extensive spectroscopic data analysis, and the electronic circular dichroism (ECD) calculation, Gauge-Including Atomic Orbitals (GIAO) NMR calculations and Mo₂(OAc)₄-induced electronic circular dichroism experiments were used to establish their absolute configurations. Compound 1, with two epoxy groups located at the 10-membered carbocycle, is uncommon in the reported meroterpenoids from C. clavipes. All the obtained compounds (1-3) were tested for their cytotoxic activity against human tumor cell line HGC-27 by using the MTT assay. All the compounds exhibited moderate cytotoxic activities against HGC-27 cell with IC₅₀ values ranging from 33.5 to 56.6 μM.

Synthetic Biology Driven Biosynthesis of Unnatural Tropolone Sesquiterpenoids

Tropolone sesquiterpenoids (TS) are an intriguing family of biologically active fungal meroterpenoids that arise through a unique intermolecular hetero Diels-Alder (hDA) reaction between humulene and tropolones. Here, we report on the combinatorial biosynthesis of a series of unprecedented analogs of the TS pycnidione 1 and xenovulene A 2. In a systematic synthetic biology driven approach, we recombined genes from three TS biosynthetic gene clusters (pycnidione 1, xenovulene A 2 and eupenifeldin 3) in the fungal host Aspergillus oryzae NSAR1. Rational design of the reconstituted pathways granted control over the number of hDA reactions taking place, the chemical nature of the fused polyketide moiety (tropolono- vs. monobenzo-pyranyl) and the degree of hydroxylation. Formation of unexpected monobenzopyranyl sesquiterpenoids was investigated using isotope-feeding studies to reveal a new and highly unusual oxidative ring contraction rearrangement.

Structural elucidation, total synthesis, and cytotoxic activity of effphenol A

A highly substituted phenol derivative, effphenol A (1), was isolated from the deep-sea-derived fungus Trichobotrys effuse FS524. Its complete structural assignment was established through a combination of spectroscopic analysis together with single-crystal X-ray diffraction experiments and further unequivocally confirmed by a biomimetic total synthesis. Structurally, effphenol A possesses a poly-substituted 6-5/6/6 tetracyclic ring system, which represents the first case of such a skeleton found in nature. Furthermore, the cytotoxic activity of effphenol A (1) toward four human cancer cell lines was assayed.

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.

Bioactive Metabolites from the Deep-Sea-Derived Fungus Diaporthe longicolla FS429

The chemical investigation of a methanol extract of the deep-sea-derived fungus Diaporthe longicolla FS429 led to the isolation of two novel diterpenoids longidiacids A and B (1 and 2), two new polyketides (3 and 4), two new cytochalasin analogues longichalasins A and B (6 and 8) and three known analogues 5, 7, 9. Their structures were elucidated through comprehensive spectroscopic analysis, while the absolute configurations were established by the comparison of the experimental and quantum chemical calculated ECD spectra. The structure of compound 7 was confirmed through X-ray diffraction for the first time. In the bioassays compound 8 exhibited antiproliferative effects against SF-268, with an IC₅₀ value of 16.44 μM. Moreover, compounds 1 and 8 were detected to inhibit 35.4% and 53.5% of enzyme activity of Mycobacterium tuberculosis protein tyrosine phosphatase B (MptpB) at a concentration of 50 μM.