Abstract: The experiment was conducted to explore the inhibition effect of magnolol,palmatine,cortex fraxini,emodin and cortex phellodendri on avian Pasteurella multocida C48-1 determined by disk diffusion method and double dilution method. The results of vitro antibacterial effect indicated that the diameter of inhibition zone of magnolol,palmatine,cortex fraxini were 22.0,11.3,15.6 mm,and the MIC were 8,256,64 μg/mL,and the MBC were 16,512,256 μg/mL,respectively. Emodin and cortex phellodendri had no antibacterial effect on P.multocida C48-1. Magnolol had the strongest antibacterial effect, followed by cortex fraxini,and palmatine had the weakest antibacterial effect on P.multocida C48-1. When P.multocida C48-1 were cultured in the content that magnolol was 6 μg/mL,the growth rate was significantly inhibited compared with the control group. P.multocida C48-1 won’t be completely inhibited until the magnolol’s content reached 8 μg/mL. According to the results of vivo antibacterial effect, the protective rate of magnolol was up to 50% when Jianghan chickens was infected by P. multocida C48-1. This study also provides an important basis for further studying to protect avian P. multocida disease.

Key words: extracts of traditional Chinese medicine, avian Pasteurella multocida, antibacterial effect