TMKS8A, an antibacterial and cytotoxic chlorinated α-lapachone, from a sea slug-derived actinomycete of the genus Streptomyces

TMKS8A ( 1 ), a new chlorinated α-lapachone derivative, along with five known related metabolites, A80915 C ( 2 ), SF2415B1 ( 3 ), chlorinated dihydroquinone 3 ( 4 ), SF2415B3 ( 5 ), and A80915 C ( 6 ), were identified from the culture extract of Streptomyces sp. TMKS8, which was isolated from a sea slug, Paromoionchis tumidus . The structure of 1 was determined by the analysis of NMR and MS spectral data, assisted by NMR chemical shift prediction using DFT-based calculation. The absolute configuration was determined to be R by comparison of experimental and calculated ECD spectra. Compound 1 displayed antimicrobial activity against Gram-positive bacteria with MIC values ranging from 6.25 to 12.5 μg ml −1 and cytotoxicity against murine leukemia P388 cells with IC 50 9.8 μM.