Metabolomic profiling reveals activity-correlated chemotypes and strain-specific metabolites in mangrove-derived actinomycetes

Twenty non-redundant actinomycete strains were isolated from mangrove sediments collected in Quanzhou, China, and evaluated for antibacterial and cytotoxic activities. Several isolates showed pronounced bioactivities, among which Streptomyces sp. H-26 exhibited strong antibacterial effects against Escherichia coli, with an inhibition zone diameter of 21.06 mm. In addition, Streptomyces malaysiensis H-60 and Streptomyces sp. H-88 displayed potent cytotoxicity towards human cancer cell lines, with IC₅₀ values of 2.09 ± 1.57 μg/mL (HeLa) and 4.43 ± 0.31 μg/mL (A549) for H-60, and 5.80 ± 0.43 μg/mL (HeLa) and 5.63 ± 0.43 μg/mL (A549) for H-88. UPLC-QTOF-MS/MS-based metabolite profiling enabled the annotation of 47 secondary metabolites, including known bioactive polyketides and several strain-specific components lacking database matches. Correlation of metabolite profiles with bioactivities revealed distinct chemical patterns underlying strain-dependent antibacterial and cytotoxic effects. These findings highlight mangrove-derived actinomycetes as promising sources of bioactive natural products.