Abstract: This study aims to investigate the effect of flavonoids contents in Ginkgo biloba leaves on the quality, yield and flavonoid extraction rate of extract of G.biloba leaves (EGb), and provide quality standard of raw material and corresponding processing parameters for EGb production.G.biloba leaves with flavonoid content of 1.0%, 0.8% and 0.6% were applied to study the effects of the quality of Ginkgo biloba leaves on the macroporous resin purification process for ensuring the quality of EGb to meet the requirement of Chinese Pharmacopoeia. Statistic regression was used to investigate the relationship between EGb properties and the concentration and volume of ethanol for purification, respectively. These properties include flavonoid content and yield of EGb,and extraction rate of flavonoids. The results showed that the concentration of ethanol and eluent volume was positively correlated with the content of flavonoids in EGb. The yield of EGb was negatively correlated with the eluent volume and changed with the contents of flavonoids in the leaves.The quality of EGb extracted from Ginkgo Leaves with low flavonoid concentration was most sensitive to the processing parameters. The content of lactone in EGb had a positive relation with flavonoid content in Ginkgo biloba leaves. It also had a negative correlation with the flavonoid content of EGb and eluent volume. To keep the quality, processing conditions and yield of EGb stable, it was suggested to mix G.biloba leaves with different flavonoid concentration to make the flavonoid content in the leaves be 1.0%. By using twice amount of 15% ethanol to elute the resins, EGb containing more than 24% of flavonoids and 6% of lactone can be prepared with yield of 2.6% and over 66% flavonoid extraction rate.

Key words: Ginkgo biloba extract, Ginkgo leaves, flavonoid glycosides