Combination effects of baicalein with antibiotics against oral pathogens

•Baicalein was evaluated for their antimicrobial activities against eleven common bacterial species present in the oral cavity.•The synergistic effects of baicalein alone or with antibiotics were evaluated in oral bacteria.•The bacterial effect of acacetin with ampicillin or gentamicin against oral bacteria was confirmed by time-kill curve experiments.

BackgroundBaicalein 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 designIn this study, the antibacterial activities of baicalein were investigated in combination with ampicillin and/or gentamicin against oral bacteria.ResultsBaicalein 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.ConclusionThese results suggest that baicalein combined with other antibiotics may be microbiologically beneficial and not antagonistic.