New cytotoxic steroids from the gorgonian Isis hippuris. Structure–activity studies

Isis hippuris has proven to be a rich source of new cytotoxic polyoxygenated steroids. Thirteen novel polyoxygenated steroids, along with some known compounds, have been isolated from the Indonesian gorgonian I. hippuris and their structures have been elucidated by spectroscopic studies. Most of the compounds were isolated as pairs of the 3-hydroxy/3-keto steroids. Although these systems contain the same steroid nucleus, they differ in their side chains. The high number of steroids isolated and the cytotoxic activity data obtained allowed us to deduce a number of structure–activity relationships.