A new cytotoxic polyhydroxysterol, 23,24-dimethylcholest-16(17)-E-en-3 beta
,5 alpha,6 beta,20(S)-tetraol (2), together with nine known compounds was i
solated from the soft coral Sarcophyton trocheliophorum. Their structures w
ere determined by spectroscopic methods. Compound 2 showed potent growth in
hibitory activity against human HL60 leukemia, M14 skin melanoma, and MCF7
breast carcinoma cells with EC50 values of 2.8, 4.3, and 4.9 mu g/ml, respe
ctively, and exhibited minimal toxicity to normal human peripheral blood ly
mphocytes.