Antimicrobial Activity of Hydrophobic Xanthones from Cudrania cochinchinensis against Bacillus subtilis and Methicillin-Resistant Staphylococcus aureus

Ten xanthones with one or two isoprenoid groups and a prenylated benzophenone isolated from roots of Cudrania cochinchinensis (Moraceae) were tested for their antimicrobial activities against Bacillus subtilis and methicillin‐resistant Staphylococcus aureus (MRSA). Among these compounds, gerontoxanthone H exhibited considerable antibacterial activity against B. subtilis (MIC=1.56 μg/ml). Four xanthones, gerontoxanthone I, toxyloxanthone C, cudraxanthone S, and 1,3,7‐trihydroxy‐2‐prenylxanthone, showed weak antibacterial activity against the bacterium (MICs=3.13–6.25 μg/ml). These compounds also exhibited similar MIC values against methicillin‐sensitive S. aureus, MRSAs, and Micrococcus luteus.