UV Spectrophotometry of autoxidized lipid monolayers while on silica gel

Autoxidation reactions of linoleic acid and tocopherol and of mixtures of the two have been monitored in the dry monolayer state while adsorbed on silica gel, by means of silica slurry spectrophotometry and oxygen uptake measurements. The UV absorbance of the products of linoleic acid alone is similar to that of previously characterized compounds, but that from tocopherol is not referable to any oxidation products known to the authors, regardless of whether the determination is made while adsorbed on silica or on the extracted products. Two compounds, designated A and B, having absorbance in ethanol at 2610–2670 and 3000 A, respectively, are the major products of tocopherol oxidation detectable by UV above 2200 A. They are a tocopheryl quinone without a hydroxyl group and an adduct of linoleic acid and oxidized tocopherol. The product distribution suggests that tocopherol may have a restricted migration in this system.