In our continuing program to identify bioactive compounds from marine invertebrates, the MeOH/EtOAc (1:1) extract of three collections of the Madagascar sponge, Biemna laboutei, was found to be cytotoxic to a series of human tumor cells. From the two sponges, seven new guanidine alkaloids, designated netamines A-G (1-7), have been isolated and their structures elucidated. Compounds 3 and 4 were found to be cytotoxic against three tumor cells with GI50 values in the micromolar range.
- Guanidine alkaloids
- Marine sponges