Oxasetin

Ten compounds including nine phenalenone derivatives (five bipolarides and four bipolarols) and a sesterterpene acid (bipolarenic acid), were isolated from a marine isolated of the fungus Lophiostoma bipolare (BCC25910), along with the known compounds, (-)-scleroderolide, (-)-sclerodin, and oxasetin. Chemical structures were elucidated based on NMR spectroscopic data and HRESIMS analysis. In addition, the absolute configurations of the phenalenones were resolved using specific rotations and chemical means, while the relative configuration of bipolarenic acid was confirmed by X-ray crystallographic analysis. The compounds were evaluated for biological activity against the Plasmodium falciparum K-1 strain, Candida albicans, and Bacillus cereus, and for cytotoxicity against both cancerous and non-cancerous cells.

Because of the evolving resistance of microorganisms against existing antibiotics, there is an increasing need for new ones, not only in human, but also in veterinary medicine. The dichloromethane extract of a fungal strain of the genus Lophiostoma, isolated from driftwood collected from the coast of the Baltic Sea, displayed antibacterial activity against some fish pathogenic bacteria. Ergosterol epoxide (1), cerebroside C (2) and oxasetin (3) were isolated from the extract and structurally elucidated on the basis of spectroscopic data and chemical evidence. Compound 3 exhibited in vitro activity against Vibrio anguillarum, Flexibacter maritimus and Pseudomonas anguilliseptica with minimal inhibitory concentrations of 12.5, 12.5 and 6.25 microg/mL, respectively. Molecular docking studies were performed to understand the interaction of compound 3 with different macromolecular targets. Analysis of in silico results, together with experimental findings, validates the antimicrobial activity associated with compound 3. These results may be exploited in lead optimization and development of potent antibacterial agents.