Abstract:The aim was to obtain the optimal extraction technology of total flavonoids from ponkan leaves，the extraction technology of total flavonoids from ponkan leaves was optimized by response surface methodology and the antioxidant activity of total flavonoids in ponkan leaves was determined.Based on the single-factor and the Box-Behnken design，taking the total flavonoids of ponkan leaves as response values，the liquid-to-material ratio，ethanol concentration，ultrasonic temperature，and ultrasonic time were selected to perform a four-factor and three-level response surface experiment and a quadratic regression equation model was established.The anti-oxidant activity of total flavonoids on scavenging effects of·OH and DPPH·was evaluated.The results showed that the optimal process conditions were：liquid-to-material ratio 38 ∶1（mL/g），ethanol concentration of 74%，ultrasonic temperature 71℃，and ultrasonic time 26 min.Three repeated experiments under this condition showed that the average extraction yield of total flavonoids was （53.19±0.28）mg/g，and the relative error with the predicted value was 0.6%，indicated that the quadratic regression equation model had certain accuracy and reliability.The scavenging test of total flavonoids on·OH and DPPH·showed that total flavonoids had a certain antioxidant activity，and there was a dose-effect relationship between total flavonoids and the·OH and DPPH·clearance rates.The IC50of clearance rates were 146.41 mg/L and 66.56 mg/L，indicated that the total flavonoids of ponkan leaves was a potential natural antioxidant.