THEORETICAL STUDIES OF THE ANTIOXIDANT PROPERTIES OF SOME FLAVONOID CLASS OF COMPOUNDS

Antioxidants play an essential role in the inhibition of the oxidative damage of the biomolecules. Flavonoids are known as potent antioxidants and are present in abundance in many of the fruits and vegetables besides being present in a large number of medicinal botanicals. A quantitative analysis of the antioxidant activity of quercetin, luteolin,  kaempherol and taxifolin belonging to the flavonoid class of compounds, has been obtained by the determination of the structures, energetics and global reactivity descriptors in both neutral and charged states using Density Functional Theory. A comparison of the antioxidant property of these flavonoids, with those of the vitamins viz. vitamin A and vitamin E molecules, reveals that these flavonoid molecules are better candidates for electronic charge transfer to the ROS and hence possesses greater antioxidant activity. To probe the preferred site of reactivity, the Fukui function; fk- was also evaluated for each of these antioxidant molecules. The trends observed in various reactivity descriptors along with Fukui indices indicates that the substitution of B-ring and the C₂-C₃ double bond in the flavan structure is very important in determining the antioxidant properties of flavonoid molecules. The results obtained are important guidelines towards the detailed understanding of the antioxidant mechanism of these flavonoids.