Abstract: To study the ultrasonic extraction coupled with microwave treatment of Flemingia macrophylla and its antibacterial activity.The extraction yields of genistein and genistin were used as evaluation index,the single factor experiment and orthogonal experiment were used to optimize the microwave treatment-ultrasonic extraction conditions of genistein and genistin from F.macrophylla. The optimal extraction conditions were compared with ultrasonic extraction and hot water extraction.The antibacterial activities of F.macrophylla extracts and genistin were also studied.The optimal extraction conditions were as followes:microwave power 700 W,ultrasonic power 200 W,desorption agent ratio 7:1 (mL/g),microwave time 180 s,with 90% ethanol as extraction solvent,liquid/solid ratio 35:1 (mL/g),extraction temperature 80 ℃,extraction time 15 min.Under the optimal conditions,the total yield of genistein and genistin was 1.3881 mg/g,and the yield of genistein and genistin were 0.9047 mg/g and 0.4834 mg/g,respectively.It was higher than that of ultrasonic extraction and hot water extraction.The inhibitory effect of F.macrophylla extracts and genistin on three common bacteria were Staphylococcus aureus>Bacillus subtilis>Escherichia coli,but genistin had no obvious inhibitory effect on Escherichia coli. In conclusion,ultrasonic extraction coupled with microwave treatment was suitable for the extraction of genistein and genistin from F.macrophylla. F.macrophylla extracts,with good antibacterial activity,can be used as a natural food preservative.

Key words: ultrasonic extraction coupled with microwave treatment, Flemingia macrophylla, genistin, genistein, antibacterial activity