According to these studies, the antioxidant activity of flavonoids depends substantially on the number and position of hydroxyl groups in the molecule In addition, sev- eral structural elements such as o-dihydroxyl catechol structure in the B-ring, the presence of unsaturation and 4-oxo group in the C-ring are also presumed to increase the antiox- idant activity of flavonoids. The 2,3-double bond in the C-ring along with 4-oxo function in the C-ring facilitates electron delocalization from the B-ring. Moreover, hydroxyl groups at positions 3 and 5 providing hydrogen bonding to the 4-oxo group in the C-ring is another structural feature attributed to the antioxidant activity of flavonoids.