Inhibitory Effects of Isomers of Tocopherol on Lipid Peroxidation of Microsomes from Vitamin E-Deficient Rats

Abstract

NADPH-induced lipid peroxidation of hepatic microsomes from vitamin E-deficient rats has been used to assess the antioxidant effectiveness of dlα-. dα- and γ-tocopherol. 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- > γ-tocopherol. This reflected the difference in the solubility of the tocopherols in the microsomes, dlα-tocopherol being the most soluble and γ-tocopherol 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.

Key Words:

• Tocopherols
• microsome
• lipid peroxidation