Abstract:

This study focused on the position of the most active hydroxyl group, the composition of highest occupied molecular orbital (HOMO) and their relationships with the antioxidant activity of flavonoids by quantum chemistry analysis. The results showed that B ring and the hydroxyl groups on B ring made a great contribution to the antioxidant activity of flavonoids. It was concluded that molecular structure of flavonoids could be divided into three functional regions: the crucial region of antioxidant activity (B ring), the accessorial region of antioxidant activity (C ring) and the adjustable region of solubility and affinity (A ring). The division of the antioxidant functional regions suggested that the solubility of flavonoids in either water- or oil-phase could be improved by introducing hydrophilic and hydrophobic groups to A ring, which could make flavonoids fully play their antioxidant activity.

Key words: flavonoid, antioxidant, molecular modification, quantum chemistry, free radical