Abstract: In this study,methanol,acetic acid and phosphate solution were used for extracting antimicrobial peptides from dry skin of Rana chensinensis respectively. For the three extraction processes,the important process parameters such as temperature,time,extraction solution to material ratio and pH were optimized respectively by using orthogonal test L9(34) with antibacterial activity of the purified product as test index. The results showed that the optimal conditions of the methanol extraction method are 0 ℃,24 h,extraction solution to material ratio 22.5:1,and pH 5.4; For the acetic acid extraction method,they are 0 ℃,24 h,extraction solution to material ratio 22.5:1,and pH 3.0; For the phosphate solution extraction method,they ar 20 ℃,24 h,extraction solution to material ratio 22.5:1,and pH6.4. Among the three methods,the antibacterial activity of the extract obtained by the methanol extraction method is the highest. The specific antibacterial activity is increased by about 5 times through Sephadex G-25 chromatography. The purified product has some antibacterial effects against both Staphylococcus aureus and Escherichia coli.

Key words: Rana chensinensi, santimicrobial peptides, purification, antimicrobial activity