Study On Extraction, Purification And Antioxidant Activity Of Flavonoids From Ginkgo Biloba Leaves

Ginkgo biloba extracts contain lots health-beneficial functions such as antitumor, scavenging radicals, autoxidation and protection of the central nervous system. Besides, the two major active components are flavonoids and small amount of terpene lactones and the flavonoids are the largest groups of bioactive substances as the natural antioxidants from Ginkgo leaves. This study is based on the efficient use of Ginkgo biloba leaves, in addition, the development of simple and reliable methods for the extraction and determination of effective components in Ginkgo biloba leaves is essential.The technology of total flavonoids extracted from Ginkgo biloba leaves by cellulase-microwave assisted method was studied. Ethanol extraction, cellulase-assisted extraction and microwave-assisted extraction were compared and the results indicated that the extraction yield was significantly enhanced by cellulase-microwave assisted method. A good yield 3.96% of total flavonoids from ginkgo biloba leaves was efficiently extracted at the optimum conditions:5% of the cellulase, hydrolysis time for 1h, and hydrolysis at 50 "C,2 mins for total microwave radiation,70% ethanol concentration, and ratio of liquid to solid was 30:1, which is 2.6 times than that by using conventional extraction method. Besides, the microstructure of Ginkgo leaves with different broken with different extraction methods was observed by scanning electron microscope (SEM) and the microstructure of Ginkgo biloba leaves was broken after the cellulase treatment and the microwave radiation, what’s more, the Ginkgo biloba leaf cell walls become more loose because of the cellulase hydrolysis, and the cell walls of Ginkgo biloba leaves were damaged by microwave radiation.The results indicated that the extraction yield was significantly enhanced with cellulase-microwave assisted method.The D-101 macroporous adsorption resin was used to purify the extracts, and the purity of total flavonoids has increased from 10.34% to 39.50%, the purity has been evaluated by the high performance liquid chromatogram. Besids, the costs and benefits of product were preliminary estimated.Antioxidant performance of extracts of Ginkgo biloba leaves and vitamin C were investigated with total reduction ability, hydroxyl free radical system, superoxide anion free radical system, In the end, the scavenging rates of the present extract on hydroxyl radical and radical superoxide were 85% and 86.18% at concentrations of 4 mg/ml, that the antioxidations from extracts were better than vitamin C. In the end, The stability of flavonoids extracted was studied, the content of Ginkgo flavonoids had decreased for 10.9% with light illumination afeter 7 days, and that had decreased for 14.7% in 80℃ for 10h,biesides, the flavonoids from Ginkgo biloba leaves were stable at pH=6.0～7.0.The content had decreased for 14.7% at pH=3 and 25.8% at pH=10 less. In addition, Na+and K+ exhibit little effect on the stability of Ginkgo flavonoids, however, Cu2+and Fe3+ have have obvious influence on the stability of flavonoids, the absorbance of Ginkgo flavonoids had reduced for 28.9% with Cu2+but raised 51.5% with Fe3+.