Cytotoxic Bisindole Alkaloids from a Marine Sponge Spongosorites sp.

Three new bisindole alkaloids of the hamacanthin class (<BO>1</BO>−<BO>3</BO>) and one new bisindole alkaloid of the topsentin class (<BO>6</BO>) were isolated along with known bisindole alkaloids (<BO>4</BO>,<BO> 5</BO>,<BO> 7</BO>−<BO>11</BO>) from the MeOH extract of a marine sponge Spongosorites sp. by bioactivity-guided fractionation. The planar structures were established on the basis of NMR, MS, and IR spectroscopic analyses. Configurations of compounds <BO>1</BO>−<BO>4</BO> were derived from ¹H NMR data and optical rotation. Compounds <BO>1</BO>, <BO>4</BO>, <BO>5</BO>, and <BO>11</BO> showed moderate to significant cytotoxicity against five human tumor cell lines, and compounds <BO>1</BO>−<BO>5</BO> showed weak antibacterial activity against clinically isolated methicillin-resistant strains.