The chemistry of the demosponge Dysidea fragilis from the Lagoon of Venice

In a study of the filtering organisms of the lagoon of Venice a series of specimens of the cosmopolitan keratose sponge Dysidea fragilis has been examined. This study led to the isolation of two new sesquiterpenes, 4 and 5, in addition to three known sesquiterpenoids (1-3) isolated previously from different sources. The remarkable differences existing. between the secondary metabolites of Venice sponges and those reported in the literature, for specimens from other geographic localities, still remain unexplained. They may be related either to real specific differences or less probably to a geographic influence on the metabolites production.