Abstract:Pueraria lobata was used as raw material in this experiment，ultrasonic-assisted extraction and response surface methodology was used to optimize the extraction process of Pueraria lobata isoflavone and its antibacterial activity.A quantitative analysis method was established for determination of isoflavone content by ultraviolet spectrophotometry with Puerarin as reference substance.Based on single factor，ratio of water to materials，ethanol concentration and extraction temperature were optimized by the Box-Behnken design and response surface method，and the yield of isoflavones from Pueraria lobata was used as the responsive values by ultrasound-assisted extraction.The bacteriostatic effect of isoflavone on two kinds of bacteria and two kinds of mold was preliminarily studied by bacteriostatic circle method.The results showed that the optimum conditions for ultrasonic-assisted extraction of Pueraria isoflavones were as follows：the ethanol concentration was 60%，the power of ultrasound was 300 W，the extraction temperature was 50℃，the ratio of liquid to material was 20 ∶1（mL/g），and the extraction time was 60 min.Under these conditions，the extraction yield of isoflavones could reach up 2.11%.The antimicrobial effect of isoflavones on various bacteria was as follows：Escherichia coli＞ Bacillus subtilis，which has no antimicrobial effect on Aspergillus niger and Penicillium niger；and with the increase of the concentration of isoflavones，the antimicrobial effect was more obviously.