Antibacterial and Synergistic Activity of Prenylated Chalcone Isolated from the Roots of Sophora flavescens

7,9,2`,4`-Tetrahydroxy-8-isopentenyl-5-methoxychalcone (THIPMC), isolated from the roots of Sophora flavescens Ait., was found to be active against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), either alone or in combination with ampicillin (AM) or gentamicin (GM), vis checkerboard assay. Minimum inhibitory concentrations ranged from 1 to 8 ?g/mL for THIPMC, from 128 to 1024 ?g/mL for AM, and from 128 to 512 ?g/ mL for GM, respectively. The combinations of THIPMC plus AM or GM yielded a fractional inhibitory concentration index ranging from 0.188 to 0.375 ?g/mL, thereby indicating a synergistic effect. These findings suggest that THIPMC alone or in combination with antibiotics against MRSA might be useful for controlling MRSA infections. However, VRE infection was only effectively treated by THIPMC alone.