Role of radical cations in the activity mechanism of antioxidants in a series of 2,6-dialkyl substituted phenols by the example of the oleic acid oxidation

Electrochemical Behavior of Tocopherols on Microelectrodes in Acetic Acid Medium

“…From this slope, the diffusion coefficient was calculated via Equation 1 to be 6.6 Â 10 À6 cm 2 s À1 , assuming that n 1. Support of this assumption follows from the results of a-TOH oxidation obtained by Berberova et al [3] and Webster in [13] in other solvents with the use of ESR spectroscopy. Figure 2 presents the semilogarithmic analysis of the first wave for the anodic oxidation of a-TOH in both background electrolytes (curves a and b).…”

“…A close difference between these oxidation potentials (about 0.7 V) was reported by Barberova et al [3] in methylene chloride ± acetonitrile mixed solvent. Likewise, the distance from the adjacent d-TOH oxidation process is sufficiently great (above 0.4 V).This fact enables a simple voltammetric determination of a-TOAc in the presence of a-TOH and other tocopherols.…”

“…The tocopherols represent one of the largest groups of natural lipid-soluble phenolic antioxidants commonly known as vitamin E [1]. aTocopherol (a-TOH) is chemically and biologically the most active species which inhibits the free-radical-chain autoxidation of polyunsaturated fatty acid and their esters [2,3]. Les active components of vitamin E are b-, g-and dtocopherol, which have fewer methyl groups attached to the phenolic ring than has a-tocopherol.…”

“…In pharmaceutical agents, vitamin E is usually employed as a-tocopheryl acetate (a-TOAc), which must be hydrolysed in the living organism to give the biologically active phenol. Tocopherols are natural antioxidant compounds found in vegetable oils, which prevent autoxidation of fatty acids in the presence of oxygen [3]. The content of tocopherols in these products indicates not only their nutritive quality, but also the oxidative stability and durability.…”

“…The electron transfer was followed by a bimolecular chemical reaction. More recently, Berberova et al [3] reported the anodic oxidation of a-TOH and atocopheryl acetate in methylene chloride ± acetonitrile (1 : 1 vol/vol) mixed solvent and proved the formation of appropriate cation radicals during this process.…”