Optimization of microwave-assisted extraction of flavonoids from Eucommia ulmoides leaf and investigation of their antioxidative effect

Using response surface methodology (RSM) to deal with the optimization of process conditions for the microwave-assisted extraction of total flavonoids from Eucommia ulmoides leaf, and their antioxidative effect in vitro was investigated.Based on single factor experiments, a quadratic regression model was established to indicate the individual and interactive effects of solid to liquid ratio, extraction time, microwave power, and ethanol concentration on the yields of naringin and hesperidin according to the Box-Behnken experimental design.From the response surface for the model, the optimal extraction conditions were obtained as follows:powder size 100 mesh, solid to liquid ratio 60:1 (mL/g) , extraction time 5.3min, microwave power 757W, and ethanol concentration 67% (v/v) .Under these conditions, the actual yields of naringin and hesperidin were 69.02mg/g and 4.96mg/g respectively, which were agreement with the theoretically predicted values.Eucommia ulmoides leaf flavonoids revealed a relatively better scavenging effect on DPPH radicals and hydroxyl free radicals than V C.Therefore, Eucommia ulmoides leaf flavonoids are effective as novel natural antioxidants.