Antibacterial Activity of the Ethanol Extract of Paeonia lactiflora on Growth of Oral Bacteria

The roots of Paeonia lactiflora Pallas are important crude drugs in Korean traditional medicine. A decoction of the dried root has been used in the treatment of rheumatoid arthritis, systemic lupus erythematosus, dysmenorrhea, hepatitis, muscle cramping, inflammation, spasms, and fever and stimulate blood circulation. In this study, the combination effect of the ethanol extract of Paeonia lactiflora (PLE) was evaluated against oral bacteria, either alone or with antibiotics, via broth dilution method and checkerboard and time kill assay. In these results, MIC/MBC values for PLE against all the tested bacteria ranged between 250-2000/250-2000 microg/mL, for ampicillin 0.031-16/0.125-32 microg/mL, gentamicin 2-256/4-512 microg/mL, erythromycin 0.008-32/0.016-64 microg/mL, and vancomycin 0.5-64/1-128 microg/mL, respectively. Furthermore, the MIC and MBC were reduced to one half-four as a result of the combination of PLE with antibiotics. Six hours of treatment with 1/2 MIC of PLE with 1/2 MIC of antibiotics resulted from an increase of the rate of killing in units of CFU/mL to a greater degree than was observed with alone. These results suggest that the ethanol extract of Paeonia lactiflora (PLE) is important in the antibacterial actions of oral pathogen agents.