Thermodynamic study of vitamin B6 antioxidant potential

For the aromatic OH group in pyridoxine, pyridoxal, pyridoxamine (vitamin B6 components) and their metabolite pyridoxic acid, reaction enthalpies related to various mechanisms of primary antioxidant action, i.e. Hydrogen Atom Transfer (HAT), Single Electron Transfer-Proton Transfer (SET-PT) and Sequential Proton-Loss Electron-Transfer (SPLET) were investigated. B3LYP, M05-2X and M06-2X functionals were employed in this study. Two solvation models were used for the solution-phase calculations in benzene and water: integral equation formalism polarized continuum model, IEF-PCM, as well as newer SMD method. All computational approaches provide identical trends. Comparison of found results with data obtained previously for phenol, alpha-tocopherol and flavonols indicates that vitamin B6 may show weaker antioxidant effect than naturally occurring phenolic antioxidants. (C) 2015 Elsevier B.V. All rights reserved.