Purificaiton, Component Analysis And Anti-oxidant Activity Of Ginkgo Biloba Exocarp Polysaccharide

Ginkgo biloba is one of the most ancient and valuable medicinal plant, its leaves, seeds and exocarp are all worthy to be developed for pharmaceutical utilization. There are many Ginkgo biloba leave preparation prevailing in the world market, and many nutritional food made by ginkgo fruit, but no exocarp product are available. China is the main habitat of Ginkgo biloba, large quantity of Ginkgo biloba exocarp were discarded as waste after fruit were collected, whereas this part of the plant have many pharmacological activity, it will bring remarkable ecological and economical benefits if Ginkgo biloba was comprehensively and properly developed.This work focus on the optimization of GBEP extraction, crude polysaccharide purification, primary characterization and GBEP antioxidant activity assay. At first, optimum extracting condition was investigated, which was to extract at 100℃for three times, with material to solvent as 1:20.Three deproteinization methods: trichloroacetic acid treatment, Sevag method, enzyme treatment and were evaluated, with protein removal rate and polysaccharide loss rate as efficiency criteria. Enzymatic method exhibits the minimum polysaccharide loss, while protein could be completely removed by Sevag method.The weight-average molecular weight of deproteinized polysaccharides was determined through high-performance gel-permeation chromatography. The deproteinized GBEP was fractionated by DEAE Sepharose Fast Flow. Five fractions waere obtained, natural polysaccharide (GBEP-N) and four acidic polysaccharide. GBEP-N and GBEP–A3 were further purified on by Superdex 200 chromatography, HPGFC indicated two homogenized polysaccharide were obtained by this method.Gas chromatography analysis indicated natural GBEP are mainly made up of arabinose, galactose, mannose glucose and rhamonse, with the relative ratio of 1.76:2:1.53:1:2. Acidic polysaccharide GBEP-AA was mainly composed of ten monosaccharides, ie. manose, rhammnose, glucuronic acid, galacturonic acid, galactosamine, glucose, galactose, xylose, arabinose, and fructose, with the molar ratio of 11.85:15.98:1:5.05:1:5.98:193.52:3.34:14.56:2.67, indicating GBEP contains more monosaccharide than just glucose, fructose, galactose and rhamnose reported by Song et al.The crude GBEP exhibited certain antioxidant activity. At the concentration of 5mg/mL, GBEP have a stronger scavenging effect of hydroxyl radical than the positive control ascorbic acid.