Quantitative comparison of the actual antioxidant activity of Vitamin C, Vitamin E, and NADH

Abstract

AbstractThe object of this fundamental research would reveal the actual antioxidant ability of the antioxidants using thermo‐kinetic parameter ΔG≠o which was proposed according to Zhu kinetic model. Kinetic experiments on the reactions between Vitamin C, Vitamin E, and NADH analog (BNAH) with DPPH• and tBu3PhO• radicals were made to measure the reaction rate constants in acetonitrile at 298 K. The ΔG≠o (XH) values of Vitamin C, Vitamin E, and BNAH in acetonitrile at 298 K were estimated, and the bond dissociation free energies ΔGo (XH) and kinetic intrinsic barriers ΔG≠XH/X of these three antioxidants to release hydrogen atoms were also compared. Only the data of thermo‐kinetic parameters ΔG≠o (XH) are consistent with the true oxidation sequence. The order of the actual antioxidant activity of these three antioxidants is Vitamin C > Vitamin E > NADH. All our preliminary results throw light on the nature of actual antioxidant ability of antioxidants, which not only depend on thermodynamic driving force, but also depend on the dynamic resistance. Therefore, thermo‐kinetic parameter ΔG≠o is the perfect parameter which can be used as measurement criteria of the actual antioxidant ability of antioxidants.