Molecular Modelling and Natural Polyphenol Compounds

Over the past decade the antioxidant properties of natural polyphenols have become very popular. Numerous in vitro, in vivo and epidemiological studies have demonstrated the beneficial effects of diets rich in fruit, vegetables, spices and beverages made from fruit and plants. These effects are attributed partly to vitamins and partly to polyphenols. It is now well-admitted that polyphenols inhibit the proliferation of some cancer cells.^1,2 Most of these compounds have the ability to reduce oxidative stress and consequently to prevent DNA damage, cardiovascular diseases, aging…^3,4 As antioxidants, they can (i) directly scavenge free radicals,⁵ (ii) inhibit lipid peroxidation, (iii) chelate metals, (iv) inhibit enzymes involved in oxidative stress⁶ and (v) stimulate the natural protective mechanisms.⁷

In the present paper we are focusing on the first type of antioxidant action, i.e. free radical scavenging. Numerous experimental data have been collected in the literature over the past twenty years allowing to rank the numerous polyphenolic compounds according to their effectiveness as radical scavengers.⁵ More recently theoretical studies (especially those based on the Density Functional Theory) have allowed to better understand this antioxidant capacity of polyphenols.^8-14 Quantum chemistry has appeared as a very effective tool to bring into evidence and to confirm the structure activity relationship of different series of compounds.