Purification of flavonoid from Gingko biloba extract by zinc complexation method and its effect on antioxidant activity

The present study was focused on investigating the method for purification of the flavonoid from the Gingko biloba extract (EGb). The flavonoid content was increased from 24% to 55% by the method of the flavonoid–zinc complexes, which was based on the chelating activity of the flavonoids. The purification process parameters optimized were 9.50, 0.20 and 1.0% (w/v, of the methanol) for solution pH value, zinc sulfate EGb ratio (w/w), and the EGb concentration, respectively. The flavonoid ingredients changes after the purification were determined by high performance liquid chromatography (HPLC) and the results revealed that this purification method exhibited high selectivity of flavonoids which had the aglycone of quercetin and kaempferol. The antioxidant activity of the extract before and after purification was compared by the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical-scavenging activity method. The results showed that the antioxidant activity of the extract was almost not affected through the purification by complexation method.