Optimization of Ultrasonic Enzymatic Extraction of Flavonoids from Mulberry Seed and Its Antibacterial and Antioxidant Activities

Using complex enzyme-assisted extraction method to extract mulberry flavonoids and analyze its antioxidant activity and antibacterial activity. The effects of different enzyme ratio, enzyme addition, enzyme hydrolysis temperature, enzymolysis time and ultrasonic time on the extraction process of flavonoids were investigated by single factor tests and Box-Behnken response surface analysis, and the removal of DPPH free radical, hydroxyl radical and superoxide anion radical was detected. The bacteriostasis activity was detected by the oxford cup method. The results showed that the best enzyme was a compound enzyme of 2:1 pectinase and cellulase. The optimum extraction conditions were as follows:The dosage of compound enzyme was 0.3 mg/mL, the temperature of enzymolysis was 55℃, the time of enzymolysis was 80 min, and the time of ultrasound was 20 min.Under these conditions, the extraction rate of flavonoids from mulberry seeds was 5.32 mg/g. The extraction of flavonoids had a high antioxidant activity, and the antioxidant activity had a certain effect on the concentration of flavonoids, among which the hydroxyl radical scavenging effect was the strongest. When the concentration of flavonoids was 1.00 mg/mL, the scavenging rate of DPPH free radical and hydroxyl radical was 83.90% and 87.27% respectively, and the activity of anti-superoxide anion radical was 165.51 U/L. The flavonoids of mulberry seed had inhibitory effect on Salmonella, Escherichia coli, Staphylococcus aureus and yeast, and the minimum inhibitory concentration was 0.75, 1.50, 1.00 and 2.00 mg/mL, respectively.