Objective:To evaluate the antibacterial activities of five Chinese medicines and their chemical constituents against five multidrug-resistant clinical bacteria isolates. Method: A micro-twofold dilution method was performed to detect the minimum inhibitory concentration (MIC). The growth curve of bacteria was recorded by measuring A595 successively and the protein expression profile was mapped by SDS-PAGE. Result: Rhei Radix et Rhizoma was effective against the strains of Staphylococcus aureus and Enterococcus faecalis with the MIC of 6.25-12.50 g · L-1. Caryophylli Flos exhibited a broad spectrum actibity and suppressed all the tested bacteria isolates to grow with the MIC of 3.13-25.00 g · L-1. The rest medicines

namely Taraxaci Herba

Lonicerae Japonicae Flos and Curcumae Longae Rhizoma appeared no antibacterial activities.No monomer constituents show antibacterial activities against pseudomonas aeruginosa. Emodin

aloe-emodin and eugenol showed better antibacterial activities against G-negative bacteria than other bacterial isolates. Emodin was observed with the MIC of 1.95-15.63 mg · L-1and aloe-emodin with the MIC of 2.34-75.00 mg · L-1. Eugenol was the only constituent that could suppress Acinetobacter baumanii with the MIC of 5.32-10.64 mg · L-1. No antibacterial activity of curcumin

caffeic acid and chlorogenic acid was found. Growth suppression and changes of protein expression were observed with strains of S. aureus in the presence of emodin. Conclusion: Rhei Radix et Rhizoma and Caryophylli Flos

as well as their chemical constituents

emodin

aloe-emodin and eugenol

can significantly inhibit some multidrug-resistant clinical bacteria strains. Emodin

aloe-emodin and eugenol play an important role in the antibacterial activities of these two Chinese medicines

respectively. The further researches would be carried out to elucidate their exact functional mechanism.