To discover new lead compounds against methicillin-resistant Staphylococcus aureus (MRSA), trimethylhydroquinone, vitamins K 1 , K 2 , K 3 and menadione sodium bisulfite were targeted for anti-MRSA assay. Their anti-MRSA activities were evaluated by agar diffusion method, and their minimum inhibitory concentrations (MICs) were determined by broth microdilution method. The results showed that trimethylhydroquinone, vitamin K 3 and menadione sodium bisulfite presented obvious anti-MRSA activity,

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... nd their MICs against MRSA ATCC 33592 and three clinical MRSA isolates were successively 16 to 32, 8 to 16 and 16 µg/ml. Vitamins K 1 and K 2 showed no anti-MRSA activity when the test discs respectively carried 1024 µg of them. These indicated that the anti-MRSA activity would disappear when the methyl of vitamin K 3 was substituted by alkyl that contained four isopentenyl units, and vitamin K 3 probably has an ancillary effect on the treatment of MRSA infection.