Antibacterial anthraquinone dimers from marine derived fungus Aspergillus sp.

As a continue investigation of the bioactive secondary metabolites from marine derived fungi, two new anthraquinone dimers (1, 2), along with three known anthraquinones (3-5) and two known xanthones (6, 7) were isolated from the marine-derived fungus Aspergillus versicolor. Their structures, including the absolute configurations, were elucidated by NMR, HRMS, and comparison with reported ones. Among them, compounds 1 and 2 were identified as anthraquinone dimers which dimerized by a rare C-O-C ether linkage, and both of them showed selective antibacterial activity against Gram-positive Staphylococcus aureus; whilst compound 6 exhibited moderate cytotoxicity against human cancer cell lines.