Abstract
Gynostemma pentaphyllum saponin has a variety of biological properties. Classic separation methods of saponin, such as resin absorption and preparative chromatography are limited by environmental pollution and high cost. In the study, ultrasonic assisted membrane separation was firstly used to purify saponin from Gynostemma pentaphyllum. Total proteins, polysaccharides, saponin, gypenoside A and rutin were selected as indexes to optimize the pretreatment and purification parameters by response surface methodology. The fitted models were significant (p < 0.05) and the optimal conditions were: (1) removing protein and polysaccharides by MWCO 10,000 Da, ultrasonic power 400 W and pH 7.8; (2) separation flavonoids from saponin by MWCO 1000 Da, ultrasonic power 300 W and pH 7.9. The difficulty in separating saponin from flavonoids was solved by releasing flavonoids from micelles with ultrasonic assisted membrane method. The saponin content in Gynostemma pentaphyllum extracts reached 82.81%, which was more than four times of that obtained with resin adsorption method. The protective effect of saponins on SH-SY5Y cells injury induced by H(2)O(2) was better than that of Gynostemma pentaphyllum extracts. The study suggested that ultrasonic assisted membrane method would be widely applied in the preparation of food materials.