Reaction Kinetics of α-Tocopheroxyl Radical with Biologically and Pharmacologically Active Substances

Abstract

The α-tocopheroxyl radical (αTR·) generated in the reaction with 1,1-diphenyl-2-picrylhydrazyl in n-butanol decayed according to second-order kinetics with a rate constant k_α = 3.10³ M⁻¹s⁻¹ as determined by EPR spectroscopy. Various biologically and pharmacologically active substances like isoprenaline (ISO), epi nephrine (EPI), histamine (HIS), stobadine (STO), nafazatrom (NAF) and Kampo C medicine (KMC) accelerated the decay rate of αTR·, The whole process is formally a third-order reaction with the rate constants (in 10⁹ M⁻²s⁻¹): k_s(ISO) = 1.28, k_s(NAF) = 1.25, k_S(EPI) = 0.6, k_s(HIS) = 0.4, and k_s(STO) = 0.1. In the kinetics of the reaction mechanism, bimolecular intermediates are assumed and the rate constants of their formation were determined.

Key Words:

• α-tocopherol
• α-tocopheroxyl radical
• reduction
• kinetics