Chlorinated metabolites with antibacterial activities from a deep-sea-derived Spiromastix fungus

Chromatographic separation of the solid cultures of a deep-sea-derived Spiromastix fungus (MCCC 3A00308) resulted in the isolation of eight compounds. Their structures were identified on the basis of the spectroscopic data. Compounds 1-8 are classified as depsidone-type (1-4), isocoumarin-type (5 and 6), and benzothiazole-type (7 and 8), of which 1-7 are new compounds and 1-3 along with 5 and 6 are chlorinated. Compound 3 is characterized by trichlorination and shows potent activities against Gram-positive pathogenic bacteria including Staphylococcus aureus ATCC 25923, Bacillus thuringiensis ATCC 10792, and Bacillus subtilis CMCC 63501, with minimum inhibitory concentration (MIC) values ranging from 0.5 to 1.0 μg mL^-1. This study extends the chemical diversity of chlorinated natural products from marine-derived fungi and provides a promising lead for the development of antibacterial agents.