New bisindole alkaloids of the topsentin and hamacanthin classes from the Mediterranean marine sponge Rhaphisia lacazei.

Chemical investigation of the Et(2)O extract of the marine sponge Rhaphisia lacazei resulted in the isolation of 13 pure bisindole alkaloids (1-13). Compounds (1-6) belong to the class of topsentins and have already been described. Compounds 7-13 are new products, closely related to the class of hamacanthins. The major compounds 1-3 were tested in vitro for antitumor activity; compounds 2 and 3 showed antiproliferative activity against human bronchopulmonary cancer cells (NSCLC-N6) with an IC(50) of 12 and 6.3 microg/mL, respectively.