First Principle Molecular Dynamics of the Oxidation of Methyl‐Hydroxybenzoic Acid Esters by Hydroxyl Radical in Water: Importance of the Number of Hydroxyl Groups

Abstract Hydroxyl radical is the most harmful specie in living cells. It is involved in a lot of diseases and in radiation biology. However its reactivity in aqueous medium is not completely understood. In this study, the oxidation of three esters of substituted benzoates, methyl gallate, methyl 3,4‐dihydroxybenzoate and methyl 3‐hydroxybenzoate in clusters of fifty water molecules, was analyzed by ab initio molecular dynamics using Carr‐Parrinello (CPMD) code. The two previous molecules are major metabolites of antioxidant polyphenols contained in green tea and possess significant biological activities. The three compounds, that differs only by their number of hydroxyl groups, present completely different reactivity towards hydroxyl radical. The two previous give an electron to the radical through “wires” of water molecules. The reaction occurs when the two reactants are relatively far from each other, excluding other type of reaction. Hydroxyl radical reacts with methyl 3‐hydroxybenzoate when the two reactants are in contact. Two kinds of reactions have been observed: addition to the ring in position ortho or para to hydroxyl group or donation of a hydrogen atom.