Abstract:The aims of the present study were to determine the optimal method for ultrasound-assisted total flavonoid extraction from Brassica juncea，and to evaluate lipid antioxidant activity of the extract.Four singlefactor experiments were performed，evaluating impact of ultrasonic time，liquid-to-material ratio，ethanol concentration，and ultrasonic temperature on total flavonoid extraction yield.Using a Box-Behnken design for response surface methodology，the optimal combination of factors was predicted.Total flavonoid lipid antioxidant activity was assessed in soybean oil and lard.Optimal extraction process conditions were predicted to be as follows：ultrasonic time of 25 min，liquid-to-material ratio of 30∶1（mL/g），ethanol concentration of 76%，and ultrasonic temperature of 71 ℃.Empirical total flavonoid extraction yield was 26.82 mg/g（relative error：0.45%），while predicted extraction yield of the theoretical optimal process was 26.94 mg/g.Findings demonstrate that the quadratic polynomial regression model accurately and reliably predicts optimal conditions for ultrasound-assisted total flavonoid extraction from B.juncea.Total extracted B.juncea flavonoids exhibited dose-dependent antioxidant activity in both soybean oil and lard，indicated the potential utility of this extract as an oil product additive able to prolong shelf-life.