Marine spongean cytotoxins.

Elucidation of naturally occurring toxins is very important from various points of view. Of these toxin studies, search for cytotoxins which show selective toxicity against tumor cells is a challenging subject of study. In search of new bioactive substances from marine organisms, we have been investigating cytotoxic constituents in marine sponges. Through bioassay-guided separation of marine spongean extracts by use of L1210 and KB cell lines, we isolated several potent cytotoxins. This article reviews our recent investigations of three spongean cytotoxins: 1) altohyrtin A and its allied compounds (macrolides, IC50 0.01-0.4 ng/ml (KB cells)) from Hyrtios altum, 2) arenastatin A (a depsipeptide, IC50 5 pg/ml (KB)) from Dysidea arenaria, and 3) callystatin A (a polyketide, IC50 10 pg/ml (KB)) from Callyspongia truncata.