Bioactive terpenoids from the Red Sea soft coral Sinularia polydactyla

Chemical investigation of an ethyl acetate soluble fraction of Sinularia polydactyla (Ehrenberg) led to the isolation of three known terpenoides, two of them sterols, 24-methylcholestane-3β,5α,6β,25-tetrol 25-monoacetate (1), 24-methylcholestane-5-en-3β,25-diol (2), in addition to a cembranoid diterpene, durumolide C (3), for the first time. The cytotoxicity and antimicrobial activities of the ethyl acetate extract and the isolated compounds 1–3 were evaluated in vitro. Durumolide C (3) showed selective cytotoxicity against HepG2 (IC50 1.0 μg/mL), whereas 24-methylcholestane-3β,5α,6β,25-tetrol 25-monoacetate (1) showed IC50 of 6.1 and 8.2 μg/mL against Hep2 and HCT human cancer cell lines, respectively.