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-3 beta-ol ( 5). These cholestane-type sterols possessing a 22,24( 28)-conjugated diene ( 1 and 2) in the side chain or a 5 alpha, 6 alpha-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.