Antimicrobial and Antioxidant Polyketides from a Deep-Sea-Derived Fungus Aspergillus versicolor SH0105.

Fifteen polyketides, including four new compounds, isoversiol F (1), decumbenone D (2), palitantin B (7), and 1,3-di-O-methyl-norsolorinic acid (8), along with 11 known compounds (3-6 and 9-15), were isolated from the deep-sea-derived fungus Aspergillus versicolor SH0105. Their structures and absolute configurations were determined by comprehensive spectroscopic data, including 1D and 2D NMR, HRESIMS, and ECD calculations, and it is the first time to determine the absolute configuration of known decumbenone A (6). All of these compounds were evaluated for their antimicrobial activities against four human pathogenic microbes and five fouling bacterial strains. The results indicated that 3,7-dihydroxy-1,9-dimethyldibenzofuran (14) displayed obvious inhibitory activity against Staphylococcus aureus (ATCC 27154) with the MIC value of 13.7 µM. In addition, the antioxidant assays of the isolated compounds revealed that aspermutarubrol/violaceol-I (15) exhibited significant 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity with the IC50 value of 34.1 µM, and displayed strong reduction of Fe3+ with the ferric reducing antioxidant power (FRAP) value of 9.0 mM under the concentration of 3.1 µg/mL, which were more potent than ascorbic acid.

A new epimer of azaphilone derivative pinophilin B from the gorgonian-derived fungus Aspergillus fumigatus 14-27.

A new epimer of azaphilone derivative pinophilin B, epi-pinophilin B (1), and three known analogues (2-4) were obtained from the culture of the gorgonian-derived fungus Aspergillus fumigatus 14-27. The structures of 1-4, including their relative configurations were determined by extensive spectroscopic analysis and comparing with literature data. The absolute configuration of 1 was determined by electronic circular dichroism (ECD) and optical rotatory (OR) calculations methods. Compounds 1-4 were isolated from A. fumigatus for the first time. Their antibacterial and cytotoxic activities were also evaluated.

Co-culture: stimulate the metabolic potential and explore the molecular diversity of natural products from microorganisms.

Microbial secondary metabolites have long been considered as potential sources of lead compounds for medicinal use due to their rich chemical diversity and extensive biological activities. However, many biosynthetic gene clusters remain silent under traditional laboratory culture conditions, resulting in repeated isolation of a large number of known compounds. The co-culture strategy simulates the complex ecological environment of microbial life by using an ecology-driven method to activate silent gene clusters of microorganisms and tap their metabolic potential to obtain novel bioactive secondary metabolites. In this review, representative studies from 2017 to 2020 on the discovery of novel bioactive natural products from co-cultured microorganisms are summarized. A series of natural products with diverse and novel structures have been discovered successfully by co-culture strategies, including fungus-fungus, fungus-bacterium, and bacterium-bacterium co-culture approaches. These novel compounds exhibited various bioactivities including extensive antimicrobial activities and potential cytotoxic activities, especially when it came to disparate marine-derived species and cross-species of marine strains and terrestrial strains. It could be concluded that co-culture can be an effective strategy to tap the metabolic potential of microorganisms, particularly for marine-derived species, thus providing diverse molecules for the discovery of lead compounds and drug candidates.