INHIBITORY EFFECTS OF ISOMERS OF TOCOPHEROL ON LIPID-PEROXIDATION OF MICROSOMES FROM VITAMIN E-DEFICIENT RATS

NADPH-induced lipid peroxidation of hepatic microsomes from vitamin E-deficient rats has been used to assess the antioxidant effectiveness of dlα dα and γtocopherol. When the tocopherols were added in ethanol to microsomes, the degree of inhibition of formation of thiobarbituric acid reactive substances (TBARS) decreased in the order dlα > dα > γtocopherol. This reflected the difference in the solubility of the tocopherols in the microsomes, dlαtocopherol being the most soluble and γtocopherol the least. Using inhibition of TBARS produced per tocopherol content in microsome as a measure of antioxidant potency, the effectiveness of the isomers was γ > dα > diα Despite addition of pharmacological concentrations of the isomers, it was not possible to inhibit lipid peroxidation to the same levels as were found in microsomes from vitamin E sufficient animals. Use of ethanol as a vehicle may not allow optimum orientation of the tocopherols into the lipid bilayer. © 1991 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.