Isolation, antimicrobial and antitumor activities of a new polyhydroxysteroid and a new diterpenoid from the soft coral Xenia umbellata.

A new C-30 steroid, 3β-,5α-,6β-,11α-,20β-pentahydroxygorgosterol (1), and a new diterpenoid, xeniumbellal (2), along with three known aromadendrane-type sesquiterpenes, aromadendrene (3), palustrol (4) and viridiflorol (5), were isolated from the soft coral Xenia umbellata. Chemical structures were determined by analyzing their NMR and MS data. The antimicrobial and antitumor activities of the isolated compounds were examined. Both 1 and 2 showed moderate antibacterial activities, especially against the multidrug-resistant Acinetobacter baumannii (MIC 0.22 and 0.28 mM, respectively); while 2 showed antitumor activity against a lymphoma cell line with LD50 0.57 mM and was nontoxic to Artemia salina at all tested concentrations up to about 4 mM.