Five nitro-phenyl compounds from the South China Sea mangrove fungus

Secondary metabolites from mangrove-associated fungi: source, chemistry and bioactivities

Covering 1989 to 2020The mangrove forests are a complex ecosystem occurring at tropical and subtropical intertidal estuarine zones and nourish a diverse group of microorganisms including fungi, actinomycetes, bacteria, cyanobacteria, algae, and protozoa. Among the mangrove microbial community, mangrove associated fungi, as the second-largest ecological group of the marine fungi, not only play an essential role in creating and maintaining this biosphere but also represent a rich source of structurally unique and diverse bioactive secondary metabolites, attracting significant attention of organic chemists and pharmacologists. This review summarizes the discovery relating to the source and characteristics of metabolic products isolated from mangrove-associated fungi over the past thirty years (1989-2020). Its emphasis included 1387 new metabolites from 451 papers, focusing on bioactivity and the unique chemical diversity of these natural products.

3-Nitroasterric Acid Derivatives from an Antarctic Sponge-Derived Pseudogymnoascus sp. Fungus

Four new nitroasterric acid derivatives, pseudogymnoascins A-C (1-3) and 3-nitroasterric acid (4), along with the two known compounds questin and pyriculamide, were obtained from the cultures of a Pseudogymnoascus sp. fungus isolated from an Antarctic marine sponge belonging to the genus Hymeniacidon. The structures of the new compounds were determined by extensive NMR and MS analyses. These compounds are the first nitro derivatives of the known fungal metabolite asterric acid. Several asterric acid derivatives isolated from other fungal strains have shown antibacterial and antifungal activities. However, the new compounds described in this work were inactive against a panel of bacteria and fungi (MIC > 64 μg/mL).

Anticancer effect and structure-activity analysis of marine products isolated from metabolites of mangrove fungi in the South China Sea

Marine-derived fungi provide plenty of structurally unique and biologically active secondary metabolites. We screened 87 marine products from mangrove fungi in the South China Sea for anticancer activity by MTT assay. 14% of the compounds (11/86) exhibited a potent activity against cancer in vitro. Importantly, some compounds such as compounds 78 and 81 appeared to be promising for treating cancer patients with multidrug resistance, which should encourage more efforts to isolate promising candidates for further development as clinically useful chemotherapeutic drugs. Furthermore, DNA intercalation was not involved in their anticancer activities, as determined by DNA binding assay. On the other hand, the structure-activity analysis indicated that the hydroxyl group was important for their cytotoxic activity and that bulky functional groups such as phenyl rings could result in a loss of biological activity, which will direct the further development of marine product-based derivatives.

Glionitrin A, an antibiotic-antitumor metabolite derived from competitive interaction between abandoned mine microbes

The nutrient conditions present in abandoned coal mine drainages create an extreme environment where defensive and offensive microbial interactions could be critical for survival and fitness. Coculture of a mine drainage-derived Sphingomonas bacterial strain, KMK-001, and a mine drainage-derived Aspergillus fumigatus fungal strain, KMC-901, resulted in isolation of a new diketopiperazine disulfide, glionitrin A (1). Compound 1 was not detected in monoculture broths of KMK-001 or KMC-901. The structure of 1, a (3S,10aS) diketopiperazine disulfide containing a nitro aromatic ring, was based on analysis of MS, NMR, and circular dichroism spectra and confirmed by X-ray crystal data. Glionitrin A displayed significant antibiotic activity against a series of microbes including methicillin-resistant Staphylococcus aureus. An in vitro MTT cytotoxicity assay revealed that 1 had potent submicromolar cytotoxic activity against four human cancer cell lines: HCT-116, A549, AGS, and DU145. The results provide further evidence that microbial coculture can produce novel biologically relevant molecules.