Abstract: The formulation Zhigeju was fractionated by using 3 different organic solvents and water to provide chloroform extract (CE),ethyl acetate extract (EAE),n-butanol extract (BE) and water extract (WE).Different antioxidant assays (DPPH,ABTS scavenging activity and metal chelating activity) were employed to evaluate the antioxidant activities of the four extracts.The contents of total flavonoids in different extracts were measured through UV spectroscopy using rutin as control by color reaction.The correlation between the concentration of total flavonoids and their antioxidant activities was then investigated.HPLC was used to analysis the components of the extract with the highest antioxidant activity.The results showed that the EAE had the highest antioxidant activity while the CE had the lowest antioxidant activity.All of the four extracts showed concentration dependent antioxidant activity,however the IC₅₀ values of the four extracts on antioxidant activity were different.The results of HPLC analysis showed that the main components of EAE and BE were flavonoids,including naringin,rhoifolin and quercitin.The extracts of formulation Zhigeju had the potential to be used as natural antioxidant for the drug research and related disease prevention.

Key words: formulation Zhigeju, extracts, flavonoids, free radicals, antioxidant activity