Bile acid derivatives from a sponge-associated bacterium Psychrobacter sp.

In our search for bioactive metabolites from a marine sponge-associated bacterium Psychrobacter sp., a new bile acid derivative (1), which was assumed to be an artifact, were isolated along with six known (2-7) compounds by bioactivity-guided fractionation. Elucidation of the structure of the new compound was done using a combination of NMR (H-1, C-13, HMBC, HSQC, and COSY) and MS spectroscopy. Compound 1 exhibited moderate suppressive effects on both NO and IL-6 production at a concentration of 200 mu M (87.3 mu g/mL) without significant cytotoxicity against cells. Compounds 2-5 and 7 showed selective inhibitory activity against several human pathogenic bacterial strains at the low concentration of 30 mu g/well. In a cytotoxicity evaluation, only compound 7 showed mild cytotoxicity against five human solid tumor cell lines (A-549, SK-OV-3, SK-MEL-2, XF-498, and HCT-15) with ED50 values in the range of 11-14 mu g/mL.