OBJECTIVE: To probe into the in vitro antibacterial effect of paeonol on Porphyromonas gingivalis.METHODS: Porphyromonas gingivalis was routinely cultured in vitro and co-cultured with paeonol at different concentration

1% chlorhexidine was set for positive control. The antibacterial properties of paeonol on Porphyromonas gingivalis were determined by direct contact method at the concentrations of 0

1. 5

3

7. 5 and 15 mmol/L; the number of viable bacteria of Porphyromonas gingivalis was measured by colony forming unit（ CFU） when the concentrations of paeonol were 0

1. 5

3

7. 5

15 and 20 mmol/L; the proportion of living dead bacteria in Porphyromonas gingivalis was determined by living dead bacteria staining when the concentrations of paeonol were 0

1. 5

3

7. 5

15 and 20 mmol/L. RESULTS: When the concentrations of paeonol were 1. 5

3

7. 5

15 and20 mmol/L

the OD600 of Porphyromonas gingivalis decreased significantly and presented a concentration-dependent

with statistically significant difference（ P < 0. 05）. When the concentrations of paeonol were 3

7. 5

15 and20 mmol/L

it had a certain antibacterial effect on Porphyromonas gingivalis

and the antibacterial effect turned better with the increasing of paeonol concentration

and the differences among all groups were statistically significant（ P <0. 05）. After different concentrations of paeonol（ 3

7. 5

15 and 20 mmol/L） were treated with Porphyromonas gingivalis biofilms

it was found that green fluorescence was dominant in the control group

while red fluorescence was not obvious; while in 3

7. 5

15 and 20 mmol/L group and positive control group

the red fluorescence was dominant

the green fluorescence was weak

which indicated that paeonol had significant killing effects on Porphyromonas gingivalis biofilms

and as the concentration gradually increases from 0-15 mmol/L

the killing effect turned stronger

the differences among all groups were statistically significant（ P < 0. 05）; while the paeonol had similar killing effects on Porphyromonas gingivalis biofilms at the concentration of 15 mmol/L and 20 mmol/L

there was no statistical significance in inter-group comparison（ P > 0. 05）. CONCLUSION: Paeonol has good in vitro antibacterial effect on Porphyromonas gingivalis

which can be used as one of pharmaceutical ingredients for the treatment of chronic periodontitis

with good clinical application prospects.