Abstract: Ultrasonic-microwave combined technology was used to extract polyphenols from the mulberry leaves and Folin-Ciocalte method was applied to analyze the content of polyphenols in different types and parts of mulberry leaves.The single factor and response surface methodology were successfully used to optimize the extraction conditions.Furthermore, the purification effects of different macroporous resins on the polyphenols were analyzed.The results showed that the highest content of polyphenols was 2.072 % from the type of Damodou, and the polyphenols content of Feng 24×Miao 33 was the lowest(1.035%) among eighteen varieties of mulberry leave.The optimal extraction conditions were 1 g Hu-sang87, liquid to solid ratio 20:1(mL:g), the extraction time 93 s, microwave power 326 W, ultrasonic power 304 W.Meanwhile, the yield of crude extracts was 1.598 % and the purity was 10.87 %.The most suitable resin for this purification was H103 with adsorbing capacity of 15.57 mg/g, desorption ratio of 88.67 % and short adsorption and desorption equilibrium time.The best adsorbing condition of polyphenols sample solution were adsorption column volume 40 mL, loading quantity of 15 g crude extract, mass concentration 3 g/L and the best elution conditions were ethanol volume fraction 60 %, flow rate 2 mL/min, elution volume 80 mL.Then, the purity of polyphenol increased from 10.87 % to 65.45 % under these conditions, and in the process of purification, the total yield was 84.7 %.

Key words: mulberry leaf polyphenols, ultrasonic-microwave combined extraction, response surface optimization, macroporous absorbent resins