Aragusterol C: a novel halogenated marine steroid from an Okinawan sponge, Xestospongia sp., possessing potent antitumor activity.

A novel chlorinated steroid, aragusterol C, was isolated from an Okinawan marine sponge of the genus Xestospongia. The compound strongly inhibited the proliferation of KB cells in vitro, and also showed potent in vivo antitumor activity against L1210 cells in mice. The complete structure of aragusterol C was determined by spectroscopic analysis and X-ray crystallographic analysis.