Abstract:The optimal ionic liquid-based microwave-assisted extraction process of the total flavonoids from Apocynum venetum L. leaves was investigated, and the antioxidant activity of the extract was evaluated. Firstly, the type of ionic liquid was determined in single factor experiments, and the significant factors affecting the extracted amount of total flavonoids in the process were screened out. The extraction conditions were optimized by the central composite post-design with three factors and five levels and the response surface mathematical model. The optimum process conditions were as follows: ionic liquid concentration 0.73 mol/L, liquid-solid ratio 19:1 mL/g, microwave time 10 min, microwave power 483 W, temperature 70 ℃. Under these conditions, the average extraction rate of total flavonoids was 14.10±0.202 mg/g (which was essentially consistent with the predicted value), and the extraction yield was significantly improved compared with that for the conventional extraction process. The three factors affecting the most the extraction yield were ionic liquid concentration, liquid-solid ratio, and microwave power. The results of the antioxidant activity experiments showed that the scavenging rate of ?OH radical and DPPH free radical increased with the increase of the concentration of total flavonoids from Apocynum venetum L. leaves, and exhibited a good dose-effect relationship. The corresponding IC50 values were 27.88 and 13.61 μg/mL (which were 1.71 and 2.26 times of those for Vc, respectively), indicating that the total flavonoids from Apocynum venetum L. leaves had strong antioxidant capacity.
