Abstract: To optimize the extraction process,polyphenols from Ginkgo biloba leaves was extracted with the mechanically assisted extraction method.Through single factor experiment,the effect of filling rate,ball milling speed,ball milling time,ethanol concentration,solid-liquid ratio,extraction temperature and extraction time on the yield of polyphenols from Ginkgo biloba leaves was examined.Box-Benhnken three factors three levels experiment by response surface design was carried out.Besides,the differences of extraction rate and antioxidant activity of polyphenols from Ginkgo biloba leaves by four extraction methods were compared.Results showed that the optimum extraction conditions of mechanically assisted extraction of polyphenols from Ginkgo biloba leaves were filling rate 26%,ball milling speed 400 rpm and ball milling time 15 min.Under these conditions,the yield of polyphenols from Ginkgo biloba leaves was 7.33%.The extraction yield of polyphenols from Ginkgo biloba leaves by mechanically assisted ethanol extraction method was lower than that extracted by alkaline water extraction method,but the antioxidant activity was higher than that extracted by alkaline water extraction method.The antioxidant activity of polyphenols of Ginkgo biloba leaves by mechanically assisted ethanol extraction method was similar to that extracted by ethanol reflux extraction method,but the extraction rate was higher than that by ethanol reflux extraction method.The extraction process was efficient,feasible and worth using for reference.

Key words: polyphenols from Ginkgo biloba leaves, mechanically assisted extraction, response surface method, antioxidant activity