Isolation and structure elucidation of deformylflustrabromine from the North Sea bryozoan Flustra foliacea.

The brominated pyrrolo[2,3-b]indole deformylflustrabromine was isolated as a new natural product from the bryozoan Flustra foliacea, collected in the North Sea. Deformylflustrabromine appears to be the missing link in the biosynthetic sequence from flustrabromine to flustraminol A. Flustramines A, D, and dihydroflustramine C were determined as other major constituents of the investigated sample. Deformylflustrabromine is cytotoxic against the human colon cancer cell line HCT-116 (IC50 5.8 microM).