Abstract: In this study, a coral-derived actinomycete strain was isolated from samples collected from the Xisha Islands and identified as Nocardiopsis alba SCSIO XS060 based on taxonomic characterization. Guided by the OSMAC (One Strain Many Compounds) strategy, the secondary metabolites of this strain were systematically investigated, leading to the isolation of eight natural products: nocapyrone B (1), marinactinone A (2), nocapyrone L (3), nocapyrone H (4), (2E/5Z)-2-[(4-methoxyphenyl)methylene]-5-(2-methylpropylidene)-3,6-piperazinedione (5), malassezione (6), 2-hydroxy-3-methoxybenzoic acid (7), and 1-hydroxy-4-methoxy-2-naphthoic acid (8). Antibacterial assays demonstrated that compound 5 exhibited antibacterial activity against MRSA (methicillin-resistant Staphylococcus aureus) and Staphylococcus aureus, with MIC (minimal inhibitory concentration) values of 32μg·mL^-1 and 16μg·mL^-1, respectively, while compound 2 showed weak antibacterial activity against Bacillus subtilis. Through bioinformatic analysis, cluster 9 was identified as the biosynthetic gene cluster responsible for nocapyrone production and was designated as the npr biosynthetic gene cluster. Based on the chemical structures and biosynthetic logic, a plausible biosynthetic pathway was proposed. Overall, this study demonstrated that the OSMAC strategy enabled the discovery of a series of secondary metabolites from Nocardiopsis alba SCSIO XS060, providing a new microbial resource for the production of polyketide or phenazine-related molecules.

Key words: actinomycetes, secondary metabolites, OSMAC, polyketides, phenazines