杜仲叶总黄酮微波辅助提取工艺的优化及其抗氧化活性研究

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

利用响应面曲线法对杜仲叶中总黄酮的微波辅助提取工艺条件进行优化,并测定了提取物的体外抗氧化活性。在单因素实验基础上,根据Box-Beknhen实验设计原理及响应面分析法建立了二次回归方程。以料液比、微波时间、微波功率和乙醇浓度为自变量,柚皮苷、橙皮苷得率为响应值,研究各因素及其相互作用对最终总黄酮得率的影响。利用所得模型的响应曲面图确定了微波辅助提取杜仲叶中总黄酮的最佳工艺参数为:杜仲叶粉碎颗粒度为100目、液料比60∶1(mL/g)、微波提取时间5.3min、微波功率757W、乙醇浓度67%(v/v),在此条件下,柚皮苷、橙皮苷的提取得率分别达到69.02、4.96mg/g,与理论预测值吻合。在抗氧化实验中,杜仲叶黄酮提取物表现出比VC更强的清除DPPH自由基和羟基自由基能力,作为一种天然抗氧剂具有良好的应用前景。

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 Vc. Therefore,Eucommia ulmoides leaf flavonoids are effective as novel natural antioxidants.