Theoretical Studies of the Antioxidant Properties of Some Flavonoid Class of Compounds

Antioxidants play an important role in the inhibition of the oxidative damage of the bio molecules. Flovonoids are known as potential 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 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. In order 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 clearly 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. INTRODUCTION: Free radicals 1-2 and their reactive metabolites are commonly known as reactive oxygen 1 species (ROS). Reactive oxygen species, produced in an organism, have irreplaceable role in various biochemical reactions such as hydroxylating, carboxylating, peroxidating reactions and in the reduction of rebonucleotides, besides playing important role in transmission of nerve impulse 3 at fmol concentrations. Thus, under physiological conditions a certain level of ROS is essential for metabolic processes of an organism. QUICK RESPONSE CODE DOI: 10.13040/IJPSR.0975-8232.IJP.2(7).351-61 Article can be accessed online on: www.ijpjournal.com DOI link: http://dx.doi.org/10.13040/IJPSR.0975-8232.IJP.2(7).351-61 Excess production of ROS gets triggered in response to certain stimulus. In order to deal with excess production of ROS, antioxidative protection mechanisms 4 are also in place in a health organism. Oxidative stress 4-5 is a condition of imbalance between excessive production of ROS and the endogenous antioxidative protection mechanism of an organism. Under oxidative stress condition, the excessively produces ROS such as O2 -• , • OH, • OOH, NO • , H2O2, • OONO, HOCl and 1 O2 etc., gets involved in the oxidative damage of important biological constituents i.e. lipids, proteins and DNA and hence causes very serious diseases. Atherosclerosis and cardiovascular diseases, neurodegenerative diseases such as Alzheimer„s and Parkinson„s diseases, diabetes mellitus and metabolic syndrome, skin and tumor diseases,