3β,5α,6β-Oxygenated sterols from the South China Sea gorgonian Muriceopsis flavida and their tumor cell growth inhibitory activity and apoptosis-inducing function.

Three new polyhydroxysterols, named muriflasteroids A-C (1-3) were isolated from the South China Sea gorgonian Muriceopsis flavida, together with sixteen known analogs, cholest-3β,5α,6β-triol,3β-acetate (4), 5α-methoxycholest-3β,6β-diol (5), (22E)-cholest-22-en-3β,5α,6β-triol (6), cholest-3β,5α,6β-triol (7), (22E)-24-norcholest-22-en-3β,5α,6β-triol (8), (22E,24S)-ergost-22-en-3β,5α,6β-triol (9), ergost-24(28)-en-3β,5α,6β-triol (10), (22E)-cholest-7,22-dien-3β,5α,6β-triol (11), cholest-7-en-3β,5α,6β-triol (12), (22E)-24-norcholest-7,22-dien-3β,5α,6β-triol (13), ergost-7,24(28)-dien-3β,5α,6β-triol (14), (22E,24R)-ergost-7,22-dien-3β,5α,6β-triol (15), (22E)-cholest-22-en-1β,3β,5α,6β-tetrol (16), (22E)-24-norcholest-22-en-1β,3β,5α,6β-tetrol (17), cholest-1β,3β,5α,6β-tetrol (18), and (24ξ)-ergost-1β,3β,5α,6β-tetrol (19). The structures of the new compounds were elucidated by detailed spectroscopic analysis in combination with comparison of reported data. All the compounds are reported for the first time from the animal.