A new xanthostatin analogue from the marine sponge-associated actinomycete Streptomyces sp. SCSIO 40064

A new cyclo-heptadepsipeptide xanthostatin B (1), together with isobutyryl hexapeptide (2), xanthostatin (3), TXS-1 (4) and TXS-2 (5), were isolated from the marine sponge derived Streptomyces sp. SCSIO 40064. The structures were elucidated by comprehensive spectroscopic data analyses and comparison with the literatures. The D-Val unit in 1 was assigned by Marfey's method. The absolute configuration of 4 was determined by X-ray crystallographic analysis. Compounds 1-5 were evaluated for the inhibitory activities against four pharmaceutical targets and six antibacterial indicator strains. Compound 5 displayed alpha-glucosidase inhibitory activity with IC50 value of 18.67 +/- 1.27 mu M.