Optimization of the Extraction Process for Flavonoids from Yam Bulbil and Their Antioxidant Activities

On the basis of single factor experiments, the influence of ratio of liquid, volume of ethanol, the power and time of microwave method on the yield of the flavonoids were studied.The parameters of microwave-extraction of the flavonoids was further optimized by the response surface methodology.The antioxidant activity was also studied.The optimal conditions were material-to-liquid ratio of 30:1 mL/g, ethanol concentration of 40%, microwave power of 320 W, and irradiation time of 37 s. The rate of flavonoids was 6.95 mg QE/g DW, which was just 0.7% far from the predicted value of 6.90 mg QE/g DW.It was shown that the model had good regression and high fitting degree, which could be used to predict the yield of the flavonoids.The flavonoids extracted from Yam bulbil showed the same or even greater DPPH, ABTS antioxidant activity and ferric reducing antioxidant power than VC.