Abstract
Three new polyhydroxylated sterol derivatives topsensterols A-C (1-3) have been isolated from a marine sponge Topsentia sp. collected from the South China Sea. Their structures were elucidated by detailed analysis of the spectroscopic data, especially the NOESY spectra. Topsensterols A-C (l-3) possess novel 2β,3α,4β,6α-tetrahydroxy-14α-methyl Δ(9(11)) steroidal nuclei with unusual side chains. Compound 2 exhibited cytotoxicity against human gastric carcinoma cell line SGC-7901 with an IC50 value of 8.0 μM. Compound 3 displayed cytotoxicity against human erythroleukemia cell line K562 with an IC50 value of 6.0 μM.