New cytotoxic steroids from the marine sponge Dysidea fragilis coming from the lagoon of Venice.

The sterol composition of the sponge Dysidea fragilis, coming from the lagoon of Venice, has been investigated; our results confirmed the variability of D. fragilis biochemistry. The sponge elaborates, in addition to eight usual 3 beta-hydroxy sterols, thirteen polyhydroxysterols, eight of them (6-13) were novel compounds. Their structures were established by spectroscopic data. New compounds 3 beta,5 alpha,6 beta,7 alpha-tetrahydroxy-cholest-8(9)-en-11-one (8), 3 beta,5 alpha,6 alpha-trihydroxy-9,11-secocholest-7-en-9-one (9) and 3 beta,5 alpha,6 alpha,9 alpha-tetrahydroxy-cholest-7-ene-6-sulfate (11) were proved to be cytotoxic on two different tumor cell lines in vitro.