Abstract: Objective To obtain the optimal extraction process of the flavonoid from ginkgo biloba leaves. Methods The flavonoid was extracted by borax-calcium hydrate water solution from ginkgo biloba leaves. The factors such as extraction temperature, liquid/solid ratio, borax content in aqueous solution, pH value and extraction time were optimized by the response surface methodology. Results The optimum extraction conditions were as follows：extraction temperature 90℃, liquid/solid ratio 20:1mL·g-1, borax content in aqueous solution 1%, pH value 7.42, extraction time 55.3min. Under the optimal condition, the yield of flavonoid was 85.57%. Conclusion The optimal extraction process is secure and reliable. And it’s significant for industrial production.

Key words: ginkgo biloba leaves, flavonoid, extraction process, response surface, optimization