Combination effects of baicalein with antibiotics against oral pathogens.

BACKGROUND: Baicalein is one of the major flavonoids in Scutellaria baicalensis Georgi, which has long been used in Asia as herbal medicine. Several biological effects of baicalein, such as antiviral, anti-inflammatiom, anti-hepatotoxicity, and anti-tumour properties, have been reported. OBJECTIVE AND DESIGN: In this study, the antibacterial activities of baicalein were investigated in combination with ampicillin and/or gentamicin against oral bacteria. RESULTS: Baicalein was determined with MIC and MBC values ranging from 80 to 320 and 160 to 640 µg/mL against oral bacteria. The range of MIC50 and MIC90 were 20-160 µg/mL and 80-320 µg/mL, respectively. The combination effects of baicalein with antibiotics were synergistic (FIC index <0.375-0.5 and FBCI <0.5) against oral bacteria. Furthermore, a time-kill study showed that the growth of the tested bacteria was completely attenuated after 1-6 h of treatment with the MIC50 of baicalein, regardless of whether it was administered alone or with ampicillin or gentamicin. CONCLUSION: These results suggest that baicalein combined with other antibiotics may be microbiologically beneficial and not antagonistic.