Antibacterial Activity of Flavonoids from Bauhinia Sirindhorniae

Abstract

Hexane, chloroform and 95% ethanol extracts from roots and stems of Bauhinia sirindhorniae were assayed for antibacterial activity by agar diffusion method. The results revealed that 95% ethanol extracts of roots and stems exhibited activity against Bacillus subtilis and Staphylococcus aureus. The 95% ethanol extracts from roots and stems were subjected to purification of pure compounds. Fifteen compounds were isolated and characterized. Ten of these compounds were
evaluated for antibacterial activities by broth microdilution assay. Results have shown that five compounds were found to be active. (2S)-Eriodictyol (1), isoliquiritigenin (4), isoliquiritigenin 4-methyl ether (5) were found to be active against B. subtilis with MICs of 50, 100, 200 µg/ml, respectively of and MBCs >200,
100, 200 µg/ml, respectively. They showed activities against S. aureus with the same MIC of 200 µg/ml and MBCs of 200, >200, >200 µg/ml, respectively. (2S)-Naringenin (2) and luteolin (3) exhibited antibacterial activity against B. subtilis only at MICs of 100, 200 µg/ml, respectively and MBCs of >200, 200 µg/ml,
respectively.