Extraction, Purification And Antioxidant Activity Of Ginkgo Biloba Exocarp Flavonoids

Ginkgo biloba is rich in flavonoids. But the kind and quantity of flavonoids in different part of ginkgo biloba is different. Currently, researches on ginkgo biloba is mainly about the leaves, while there is still a shortage of studying ginkgo biloba exocarp, which leads to the inadequate utilization of ginkgo biloba resource.This paper studied the optimization of extraction and purification of ginkgo biloba exocarp flavonoids, and then preliminarily discussed its antioxidant activities. Using ethanol as the solvent , the effects of temperature, concentration of ethanol, solid-to-liquid ratio, duration and times of extraction to the extraction rate of ginkgo biloba flavonoids are investigated. The optimum extracting condition investigated was to extract at 70℃in 2 hours with 80% ethanol and 25:1 liquid-to-solid ratio for 3 times. In this condition, extraction rate was 91.01%, with a 1.10% yield and a 10.38% purity.Compared the extraction efficiency of 4 extractants with degreasing rate and flavonoid loss rate, Cyclohexane was determined as the optimum extractant.Static kinetics by macroporous resins with different polarity on ginkgo biloba exocarp flavonoids have been studied. Combined various indices of static adsorption and desorpotion experiments, the optimum macroporous resin for ginkgo biloba exocarp flavonoids purification is ADS-17. Dynamic adsorption and desorption experiments by ADS-17 resin led to the result that the optimum dynamic adsorption and desorption condition of ginkgo biloba exocarp dynamic adsorption and desorption was found. By spectrophotometry, after purification the concentration of flavonoids is 53.1%.The separation effect of ginkgo biloba exocarp flavonoid aglycones by high performance liquid chromatograpy(HPLC) is investigated. The optimum separation condition is at a 335nm wavelength with methanol-0.1% phosphoric acid(60:40) solution system as mobile phase.Ginkgo biloba exocarp flavonoids also showed good antioxidant activities on the reducing power, radicals scavenging and antioxidation of bean oil.