Abstract: In this study,the antibacterial effects of plumepoppy (Macleaya cordata) extracts against Escherichia coli, Enterobacter aerogenes and Enterobacter cloacae were screened by Cylinder-plate method.Subsequently,crude extracts with good antibacterial effect was sequentially extracted with petroleum ether,ethyl acetate and n-butanol.The filter paper method was employed to study the antimicrobial activities of these fractions against the tested microorganisms. Moreover,the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were also studied.The results showed that crude extracts from different parts of M.cordata had antibacterial effect on the tested bacteria,among of which,the extracts of M.cordata roots displayed remarkable inhibition effect.In addition,the n-butanol fractions of M.cordata roots exhibited high antimicrobial activities,the inhibition zones were all over 12 mm,which were even better than their crude extracts.The MIC and MBC of E.coli were 400 μg/mL and 600 μg /mL,respectively;while the MIC (500 μg/mL) and MBC values (700 μg /mL) were the same for E.aerogenes and E.cloacae. The extracts of M.cordata roots had antibacterial effects,and the effects of n-butanol fraction were the best.

Key words: Macleaya cordata (Willd.) R.Br., bacteriostatic effect, coliforms