Characteristics of Baicalin Synergy with Penicillin or Notopterygium Ethanol Extracts Against Staphylococcus aureus

Abstract Baicalin facilitates the effectiveness of both penicillin and Notopterygium ethanol extracts (NEE) on Staphylococcus aureus . Two Staphylococcus aureus strains, ATCC29213 and 03-21 (a clinical isolate), were tested. When combined with 128 μg · mL −1 of baicalin, the minimum inhibitory concentration (MIC) of penicillin was reduced from 0.25 μg · mL −1 to 0.06 μg · mL −1 , while that of NEE was reduced from 32 μg · mL −1 to 8 μg · mL −1 against ATCC29213. Against the 03-21 strain, the MIC of penicillin was reduced from 4 μg · mL −1 to 1 μg · mL −1 , while that of NEE was reduced from 32 μg · mL −1 to 4 μg · mL −1 . Viable number counting results show that combination of baicalin and penicillin acts on the killing mechanism, while the baicalin and NEE acts on the inhibition. These results show that baicalin acts as a synergistic ally with both penicillin and NEE but has different modes of action.