Polyoxygenated sterols from the Formosan soft coral Sinularia gibberosa.

Chemical investigation on the dichloromethane-soluble fraction from the EtOH extract of Sinularia gibberosa Tixier-Durivault has led to the isolation of three new polyoxygenated sterols, gibberoketosterols B (1) and C (2) and gibberoepoxysterol (3), along with two known steroids, gibberoketosterol (4) and 24-methylenecholest-5-en-3beta-ol (5). These cholestane-type sterols possessing a 22,24(28)-conjugated diene (1 and 2) in the side chain or a 5alpha,6alpha-epoxide in the B-ring (3) were isolated for the first time from marine sources. Compound 4 showed significant inhibition against the up-regulation of the pro-inflammatory iNOS and COX-2 proteins of LPS-stimulated RAW264.7 macrophage cells, while 1 was found to be inactive. The cytotoxicity of 1-4 toward a limited panel of cancer cell lines is also reported.