Optimization of Microwave-assisted Extraction of Saponins from Gardenia jasminoides Ellis and Its Antioxidant Activity

The microwave-assisted extraction of saponins from Gardenia jasminoides Ellis powder was studied. On the basis of single factor experiment, response surface analysis was carried out with Box-Behnken design, taking microwave time, extraction time, liquid-solid ratio and ethanol concentration as factors, and saponin yield as response value. The antioxidant activity of gardenoside was studied by potassium ferricyanide reduction method and DPPH free radical scavenging rate with ascorbic acid as control. The results showed that the optimal extraction conditions for the extraction of saponins from Gardenia were microwave power 450 W, microwave time 40 s, extraction time 9.6 min, extraction temperature 50℃, liquid-solid ratio 21:1 (mL/g) and ethanol concentration 80%, respectively. Under these conditions, the yield of Gardenia saponins was 13.92%±0.04%, which had 2.05% of the relative error to the model predictive yield. The study revealed that this microwave-assisted methodology, which was simple and highly efficient, was suitable for extraction of Gardenia jasminoides Ellis saponins. And the regression model was reliable for the yield prediction in practice. The antioxidant activity study showed that abilities of saponins in Gardenia jasminoides Ellis to scavenge hydroxyl radical and DPPH were good, but its overall reducibility was lower than that of ascorbic acid.