OXYGENATED CLEROSTEROLS ISOLATED FROM THE MARINE ALGA CODIUM-ARABICUM

Clerosterol [1], (24S)-2-ethyl-3-oxocholesta-4,25-dien-6 beta-ol [2], (24S)-24-ethyl-5 alpha-hydroperoxycholesta-6,25-dien-3 beta-ol [3], (2 4S)-24-ethyl-7-oxocholesta-5,25-dien-3 beta-ol [4], (24S)-24-ethyl-7 a lpha-hydroperoxycholesta-5,25-dien-3 beta-ol [5], and (24S)-24-ethylch olesta-5,25-dien-3 beta,7 alpha-diol [6], were isolated from the marin e green alga Codium arabicum. A portion of steroid 5 was epimerized to (24S)-24-ethyl-7 beta-hydroperoxycholesta-5,25-dien-3 beta-ol [8]. LA H reduction of an inseparable mixture of 5 and 8 yielded diol 6 and (2 4S)-24-ethylcholesta-5,25-dien-3 beta,7 beta-diol [7]. Among these com pounds, sterols 2, 3, and 5 were isolated for the first time from a na tural source. Metabolites 2-6 showed significant cytotoxicity toward v arious cancer cell lines.