Effect of d,l-alpha-tocopheryl esters on vitamin E-deficient rats

Area of Science:

• Biochemistry
• Nutritional Science
• Pharmacology

Background:

• Oral administration of alpha-tocopherol esters results in variable absorption, with some intact and others hydrolyzed.
• Hydrolysis during absorption is linked to the ester group's structure at the 6-position of alpha-tocopherol.
• Understanding tocopherol ester metabolism is crucial for vitamin E research.

Purpose of the Study:

• To investigate the metabolism and biological effects of different alpha-tocopherol esters in vitamin E-deficient rats.
• To compare the effects of easily, moderately, and scarcely hydrolyzable tocopherol esters.
• To assess the impact of these esters on specific liver microsomal enzymes.

Main Methods:

• Oral administration of three alpha-tocopherol esters (acetate, nicotinate, pivalate) to vitamin E-deficient rats.
• Analysis of ester hydrolysis and absorption patterns.
• Determination of effects on liver microsomal enzymes: cytochrome P-450, cytochrome b5, aniline and hexobarbital difference spectra, and NADPH-dependent cytochrome c reductase.

Main Results:

• Easily hydrolyzable esters followed metabolic pathways similar to alpha-tocopherol.
• Moderately and scarcely hydrolyzable esters exhibited distinct physiological effects due to absorption of the unchanged ester.
• Alpha-tocopheryl pivalate inhibited NADPH-dependent cytochrome c reductase release, despite low sediment distribution, suggesting a potential membrane effect.

Conclusions:

• The degree of ester hydrolysis during absorption influences the metabolic fate and biological effects of alpha-tocopherol esters.
• Scarcely hydrolyzable esters, like pivalate, may possess unique properties distinct from alpha-tocopherol.
• Alpha-tocopheryl pivalate warrants further investigation for its potential membrane stabilizing effects.