Extraction of Flavonoids from Docynia delavayi and Their Antioxidant and Hypoglycemic Activities

Taking Docynia delavayi as the raw material, the extraction of flavonoids by ultrasonic-assisted enzymatic method was optimized using response surface methodology, and the in vitro antioxidant and hypoglycemic activities were determined. The results showed that the optimal process parameters were extraction temperature of 50 ℃, complex enzyme (pectinase and cellulase) of 3:2, extraction time of 50 min, liquid-material ratio of 30 mL/g, ethanol concentration of 55%, and pH of 4.5. Under these conditions, the yield of flavonoids from D. delavayi was as high as 13.10%, which was close to the predicted value (13.01%). In vitro antioxidant assays showed that flavonoids from D. delavayi scavenged DPPH, ABTS⁺ and hydroxyl radicals with IC₅₀ values of 0.04, 0.29 and 0.70 mg/mL, and the scavenging rates of DPPH, ABTS⁺ and hydroxyl radicals were 93.98%, 97.60% and 84.26% when the flavonoid concentrations were 0.24, 1.40 and 4.00 mg/mL, respectively. At the same time, D. delavayi flavonoids also presented certain ability to reduce iron ions, which indicated that D. delavayi flavonoids possessed strong antioxidant activities. In vitro hypoglycemic assays found that flavonoids from D. delavayi inhibited α-glucosidase and α-amylase with IC₅₀ values of 0.86 and 0.37 mg/mL, and the α-glucosidase and α-amylase inhibition rates were 81.83% and 82.72% when the flavonoid concentrations were 12.0 and 5.0 mg/mL, respectively, which demonstrated that D. delavayi flavonoids possessed excellent inhibitory ability against α-glucosidase and α-amylase. This paper would provide an experimental basis for the comprehensive development and utilization of D. delavayi.