α-Tocopherol impact on oxy-radical induced free radical decomposition of DMSO: Spin trapping EPR and theoretical studies

Abstract

EPR spin trapping and theoretical methods such as density functional theory (DFT) as well as combined DFT and quadratic configuration interaction approach (DFT/QCISD) were used to identify the radicals produced in the reaction of oxy-radicals and dimethyl sulfoxide (DMSO) in the presence and absence of α-tocopherol. Additionally, the mixtures of α-tocopherol with linolenic acid and glyceryl trilinoleate as well as bioglycerols (glycerol fractions from biodiesel production) were tested. α-Tocopherol inhibited oxidation of the main decomposition product of DMSO, •CH 3 to •OCH 3 but did not prevent the transformation process of N-t-butyl- α-phenylnitrone (PBN) into 2-methyl-2-nitrosopropane (MNP). Theoretical investigations confirmed the structures of proposed spin adducts and allowed to correlate the EPR parameters observed in the experiment with the spin adducts electronic structure.