Three new anthraquinones from the twigs of Cassia auriculata Linn. and their antibacterial activity

Three new anthraquinones (1-3), together with four known analogues (4-7) were isolated from the twigs of Cassia auriculata Linn.. Their structures were elucidated by extensive spectroscopic analysis and comparison of spectroscopic data with those reported in literatures. All compounds were tested for their anti-methicillinresistant Staphylococcus aureus (anti-MRSA) activity. Compounds 1, 2 and 7 showed modest antibacterial activity against MRSA with MIC values of 4.2, 5.0, 4.7 mu g/mL, and compounds 3, 4, 5 and 6 showed weak antibacterial activity against MRSA with MIC valves of 9.2, 7.6, 7.1, 9.6 mu g/mL, respectively.