Abstract: In this study, the OSMAC strategy was applied to explore the secondary metabolites of mangrove-derived actinomycete Streptomyces collinus SCSIO YQ03 from Zhanjiang, Guangdong Province, China. The fermentation extract was subjected to successive separation and purification using silica gel column chromatography, preparative thin-layer chromatography, and high-performance liquid chromatography. Structural elucidation of the isolated compounds was accomplished by comprehensive spectroscopic analyses, including NMR and MS, in combination with physicochemical properties and comparison with reported data. Five compounds were isolated from the ethanol extract and were identified as anthracimycin D (1), anthracimycin (2), β-rubromycin (3), γ-rubromycin (4), and 3′-hydroxy-β-rubromycin (5). Notably, compound 1 is a structurally unique polyketide formed by the coordination of three anthracimycin units with one Fe3+ ion. Biological evaluation revealed that compounds 1–5 exhibited antibacterial activity. Compound 1 showed notable inhibitory activity against Bacillus anthracis with a MIC value of 3.2μg·mL-1, while compound 2 displayed potent anti-anthrax activity with a MIC value of <0.032μg·mL-1. In addition, compounds 3–5 demonstrated pronounced activity against MRSA. These findings indicate that anthracimycin derivatives obtained from the mangrove-derived strain S. collinus SCSIO YQ03 represent promising lead compounds for the development of anti-infective agents targeting MRSA and Bacillus anthracis.

Key words: marine actinomycetes, polyketide compounds, anti-infective, anti-Bacillus anthracis