Antibiotic Bisanthraquinones Produced by a Streptomycete Isolated from a Cyanobacterium Associated with <i>Ecteinascidia </i><i>t</i><i>urbinata</i>

Abstract

Chemical studies of a streptomycete isolated from a cyanobacterium associated with the tropical tunicate Ecteinascidia turbinata led to the bioassay-guided purification of two antibacterial bisanthraquinone metabolites and a cytotoxic artifact. The structures, including relative configurations of these octacyclic compounds, were established by spectroscopic analyses. Their potent antibacterial properties (IC(50) = 0.15-130 microM) versus methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis and cytotoxic effects against HCT-116 cells are presented.