Journal of Lipid Research, Vol. 19, 416-422, May 1978
Copyright © 1978 by Lipid Research, Inc.

Interfacial oxidation of -tocopherol and the surface properties of its oxidation products

Gajanan S. Patil and David G. Cornwell

Department of Physiological Chemistry, The Ohio State University, Columbus, OH 43210

dl--Tocopherol spread on an acidic subphase as a gaseous monolayer was oxidized slowly to a derivative that was identified by thin-layer chromatography as -tocopherylquinone. The derivative generated the same II-A isotherm as -tocopherylquinone. When the subphase contained gold chloride, -tocopherol was oxidized rapidly and quantitatively to -tocopherylquinone. dl--Tocopherol spread on a basic subphase as a gaseous monolayer was oxidized slowly to a mixture that contained -tocopherol, a quinone, and a nonpolar derivative. The mixture generated a II-A isotherm with an inflection point below the equilibrium spreading pressure of either -tocopherol or -tocopherylquinone. When potassium ferricyanide was added to the alkaline subphase, -tocopherol was oxidized rapidly to a mixture that contained both the nonpolar derivative (major product) and the quinone (minor product). The nonpolar derivative was isolated by thin-layer chromatography and identified as the spirodienone ether by ultraviolet, infrared, and chemical ionization mass spectra. The spirodienone ether had a low equilibrium spreading pressure that explained the inflection point in the II-A isotherm generated by -tocopherol on an alkaline subphase. Surface area data showed that dl--tocopherol formed immiscible films with stearyl alcohol and miscible films with oleyl alcohol. II-A isotherms showed that -tocopherol in both immiscible and miscible mixtures was oxidized rapidly on an alkaline potassium ferricyanide subphase to the spirodienone ether. Collapse pressure data showed that the spirodienone ether formed an immiscible film with stearyl alcohol and a miscible film with oleyl alcohol. Interfacial oxidation experiments showed that -tocopherol is oxidized either to tocopherylquinone (acidic subphase) or to the spirodienone ether (alkaline subphase). The natural occurrence of both tocopherylquinone and the spirodienone ether suggests that several types of oxidant stress are found in biological systems. One type of oxidant stress may involve the peroxy radical generating tocopherylquinone; a second type may involve hydroxyl radical-hydroxide ion generating the spirodienone ether.

Supplementary key words phenoxonium ion • -tocopherylquinone • spirodienone ether • surface area • equilibrium spreading pressure • gold chloride • acid and alkaline subphases • potassium ferricyanide • stearyl and oleyl alcohol • miscible and immiscible films • peroxy and hydroxyl radicals

Submitted on September 6, 1977
Accepted on December 12, 1977

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