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

Chemical investigation of the Et2O extract of the marine sponge Rhaphisia L acazei resulted in the isolation of 13 pure bisindole alkaloids (1-13). Com pounds (1-6) belong to the class of topsentins and have already been descri bed. Compounds 7-13 are new products, closely related to the class of hamac anthins. The major compounds 1-3 were tested in vitro for antitumor activit y; compounds 2 and 3 showed antiproliferative activity against human bronco pulmonary cancer cells (NSCLC-NG) with an IC50 of 12 and 6.3 mu g/mL, respe ctively.