The crude ethanol extract of the leaves of Spiraea thunbergii Sieb. (Rosaceae) showed antibacterial activity against a food borne pathogen, Escherichia coli. Bioactivity-guided separation led to the isolation of a butyrolaton, 1(S-(-)-tulipalin B). The structure was determined from the interpretation of spectroscopic data (UV, MS, and NMR). The minimal inhibitory concentration (MIC) of compound 1 against E. coli was found to be 100/ml. In addition, we found the possibility that a methylene group may operate as a key factor in the antibacterial activities of compound 1 and the hydroxyl group may exert a synergistic effect with the methylene group.
Key words: Spiraea thunbergii Sieb., antibacterial activity, butyrolactones, S-(-)-tulipalin B, Escherichia coli.
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