Abstract: Antioxidant activity of different isoflavones from soybean and red clover was researched in this paper so to establish structures, which enhance the antioxidant actibity. Using alpha deoxyribose oxidation method, at concentrations of 1, 5, 10μg/ml;pyrogallol autoxidation method at concentrations of 10μg/ml and antioxidant activity to lard. Genistein showed the highest antioxidant activities but formononetin showed the lowest. Because different isoflavone contains different number of hydroxyl at different place.

Key words: antioxidant activity, free radical, isoflavones