P. Wang’s scientific contributions

The operating factors affecting the yield of microwave-assisted extracting terpene lactones from Ginkgo biloba L. were studied. Firstly, single factors including irradiation time, microwave power, ethanol concentration and ratio of ethanol to solid were investigated separately, and then the orthogonal experiments followed by the verification tests were conducted for obtaining the appropriate operation conditions. Finally, the microwave-assisted extraction (MAE) method was compared with the traditional heating reflux extraction method. Results show that the optimum extracting conditions for MAE method are as follows: the irradiation time is 8 min, the microwave power is 500 W, the ethanol concentration is 70% and the ratio of liquor to solid is 20:1. Using above conditions, the yield of terpene lactones is 1.620 mg·g-1. Compared with the traditional heating reflux extraction method, using the MAE method, the extraction yield of terpene lactones is 31% higher, the volume of solvent is reduced by 33%, and the extracting time is significantly shortened. All these show that the MAF method is a more ideal means for the extracting terpene lactones from Ginkgo biloba L.

In order to study the factors affecting the yield of essential oil extracted from Rhizoma Curcuma by using microwave-assistant extraction (MAE) technology, the single factor experiments were conducted, in which, the effects of microwave power, extraction time and used solvent amount on the extraction were studied separately. According to the results of above experiments, then the particle size, extraction time and microwave power used were selected as the factors for the orthogonal experiments to find out the optimum operating conditions for the MAE of essential oil extracted from Rhizoma Curcuma. The results of orthogonal experiments show that the optimum operating conditions found are as follows: the extracted particle size used is 38 μm, the added amount of solvent, petroleum ether, is eightfold amount of the extracted Rhizoma Curcuma powder, the microwave power used is 700 W and the extraction time is 550 s. Using the mentioned optimum conditions, the essential oil yield reaches 4.7%, and according to the analyses of gas-chromatography-mass-spectrometry (GC-MS), its contents of Curecumol, Germarcrone and β-elemene are 0.82%, 3.80% and 1.94%, respectively. Moreover, taking the essential oil yield as the target, the MAE method was compared with the water-steam distillation (SD) method and supercritical CO2 extraction (SFE) method. The results show that the MAE is high in extracting rate, oil yield and content of active constituents, also essential oil quality is good. Thus it may be considered as an ideal means for extracting essential oil from Rhizoma Curcuma.