Optimization of Extraction Technology of Total Flavonoids from Passiflora edulis peel by Ultrasonic Assisted with Complex Enzyme and Its Antioxidant Activity

The total flavonoids form Passiflora edulis peel were extracted by compound enzyme assisted ultrasonic method. Taking the yield of flavonoids as the index, the effects of the amount of compound enzyme, enzymatic hydrolysis time, liquid-solid ratio and ultrasonic time on the extraction of total flavonoids from Passiflora edulis peel were analyzed by single factor tests. The main influencing factors and optimal combination of flavonoids extraction were further analyzed by response surface test (Box-Behnken), and the scavenging rate and reducing power of DPPH free radical and hydroxyl free radical were detected in vitro. The results showed that the optimum extraction conditions for ultrasonic extraction of total flavonoids from Passiflora edulis peel assisted by composite enzyme were as follows: The ratio of cellulase to pectinase was 2:1, the dosage of composite enzyme was 4.8%, the enzymolysis time was 1 h, the ethanol concentration was 60%, the liquid-material radio was 30:1 mL/g, and the ultrasonic time was 41 min. Under the optimized conditions, the total flavonoids yield was (2.20%±0.05%), which was similar to the predicted yield 2.24% (<1%) of the regression model. The results of antioxidant activity showed that the scavenging rates of DPPH radical and hydroxyl radical were 90.8% and 84.1% when the concentration of flavonoids from Passiflora edulis peel reached 0.44 mg/mL and 44 µg/mL respectively. The extraction of total flavonoids from Passiflora edulis peel by complex enzyme assisted ultrasound could provide a way for the resource utilization of thyme peel. Based on the above research results, the total flavonoids from Passiflora edulis peel had good antioxidant activity and were an ideal natural antioxidant.