Aspergetherins A-D, New Chlorinated Biphenyls with anti-MRSA Activity from the Marine Sponge Symbiotic Fungus Aspergillus terreus 164018.

Aspergetherins A-D (1-4), four new chlorinated biphenyls, were isolated from the rice fermentation of a marine sponge symbiotic fungus Aspergillus terreus 164018, along with seven known biphenyl derivatives (5-11). The structures of four new compounds were determined by a comprehensive analysis of the spectroscopic data, including HR-ESI-MS and 2D NMR data. All 11 isolates were evaluated for their anti-bacterial activity against two strains of methicillin-resistant Staphylococcus aureus (MRSA). Among them, compounds 1, 3, 8 and 10 showed anti-MRSA activity with MIC values of 1.0-128 μg/mL. Preliminary structure-activity relationship analysis unveiled that both chlorinated substitution and esterification of 2-carboxylic acid could impact the antibacterial activity of biphenyls.