engleski

The PCET-RRC mechanism in the reaction of ferulic acid with •OH free radicals

In this report we investigated ability of ferulic acid (FA) to scavenge •OH free radicals via here proposed Proton Coupled Electron TransferRadical-Radical Coupling (PCET-RRC) mechanism. FA is a notable constituent of a diet rich in fruits and vegetables and an abundant colon catabolite of various (poly)phenolic compounds. As highly bioavailable it may appear in systemic circulation in sufficient concentrations to efficiently scavenge excess of intracellular free radical species and thus may help in suppressing oxidative stress conditions. Thermodynamic and kinetic of •OH free radical scavenging by FA were studied at M06-2X/6- 311++G(d, p) level of theory in gas-phase using Gaussian 09 program package. Features of the SOMO orbital of the ferulic acid phenoxyl group•OH free radical transition state, and QTAIM charge of the transferring H atom (qH), indicate PCET mechanism as operative pathway in scavenging of single •OH free radical specie. In addition, ability of resulting ferulic acid phenoxyl radical to scavenge another •OH free radical via RRC was considered. RRC occurs on two potential energy surfaces, the phenomenon known as two-state reactivity. RRC begins with separate reactants in doublet state which forms reactant complex in triplet state, and via spin crossing point terminates in singlet state product. For both PCET and RRC pathways reaction rates were evaluated using TheRate program. It should be noted that the final product of proposed PCET-RCC mechanism is 5- hydroxyferulic acid. It is already known that catechol moiety of this acid is able to scavenge another two •OH free radicals via formal HAT mechanism. It hich significantly contributes to overall antioxidant potency of FA.

ferulic acid ; hydroxyl radical ; PCET ; radical-radical coupling ; DFT

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