A methanol extract from grape seeds showed a potent antibacterial activity against Echerichia coli, Salmonella enteritidis, and Staphylococcus aureus. A responsible compound was isolated from the extract to be identified as gallic acid by instrumental analysis. Structure-activity correlation assays revealed that three hydroxyl groups of the compound were effective for antibacterial activity against E. coli and S. enteritidis and all of the substituents of the benzene ring were effective against S. aureus. Minimal inhibitory concentration of gallic acid against E. coli and S. enteritidis was 0.5mM and that against S. aureus was 0.3mM. Ethanol- and salt-containing foods cooperatively acted on the antibacterial activity of gallic acid.
