ANTIBIOTIC AND CYTOTOXIC ACTIVITY OF BROMINATED COMPOUNDS FROM THE MARINE SPONGE VERONGIA-AEROPHOBA

Analysis of the marine sponge Verongia aerophoba from the Canary Islands afforded eight brominated secondary metabolites including the small molecular weight compounds aeroplysinin-1 (5) and the dienone (7) which were previously shown to arise by enzymatically catalyzed degradation of aerophobin-2 (4) and isofistularin-3 (1) following breakdown of the cellular compartmentation of the sponge. All compounds were identified from their NMR and mass spectra. Aeroplysinin-1 as well as dienone which arise from isofistularin-3 or aerophobin-2 by biotransformation within the sponge showed a significantly higher antibiotic as well as cytotoxic activity than their biogenetic precursors. Antibiotic activity was studied with respect to several gram-positive and gram-negative bacteria including B. subtilis, S. auteus and E. coli. The MICs (MBCs) of aeroplysinin-l (5) and the dienone (7) varied between 12.5-25 (50-100) mu g/ml respectively. Cytotoxicity was tested in vitro towards HeLa cells, a human cervix uteri tumour cell line. Aeroplysinin-l (5) and the dienone (7) displayed pronounced cytotoxic activity with IC(50)s of 3.0 and 3.2 mu M respectively. A five-fold increase in cytotoxicity was observed after O-acetylation of the dienone (7). The IC50 of the dienone O-acetate (0.6 mu M) was comparable to that of the clinically used anticancer drug cisplatin (0.7 mu M).