Ultrasonic-enzyme synergistic extraction and antioxidant activity analysis of alfalfa polyphenols

The polyphenols from alfalfa were extracted by ultrasonic-enzyme synergistic method. The effects of liquid-solid ratio, enzyme addition volume, enzyme incubation time, ultrasonic time, ultrasonic temperature and pH on phenol yield of alfalfa were investigated, and the extraction technology was optimized by response surface experiment. The antioxidant activities of alfalfa phenols were also studied. The results showed that the optimum technology factors for extracting alfalfa phenols were as follows: enzyme addition was 4.9%, ultrasonic time was 74 min and ultrasonic temperature was 49 ℃. Under this condition, the highest extraction quantity of total phenols could reach 3.642 mg·g-1. In addition, the phenols showed strong activities for DPPH (2,2-diphenyl-1-picrylhydrazyl) and hydroxyl radical scavenging, and the half scavenging concentration (IC50) of DPPH and ·OH radicals were 10.78 μg·mL-1 and 19.28 μg·mL-1, respectively.