Polyhalogenated Indoles from the Red Alga Rhodophyllis membranacea: The First Isolation of Bromo-Chloro-Iodo Secondary Metabolites.

An unusual tetrahalogenated indole with the exceptionally rare inclusion of the three halogens bromine, chlorine, and iodine was found using mass spectrometry within a fraction of a semipurified extract obtained from the red alga Rhodophyllis membranacea. We report herein the isolation and structure elucidation, using a combination of NMR spectroscopy and mass spectrometry, of 11 new tetrahalogenated indoles (1-11), including four bromochloroiodoindoles (5-7, 10). Several were evaluated for cytotoxic and antifungal activities against the HL-60 promyelocytic cell line and Saccharomyces cerevisiae, respectively.