A. Saari Csallany

Conversion of d-α-tocopherol-C14 to tocopheryl-p-quinone in vivo☆

Abstract Following administration of d -α-tocopherol-5-methyl-C 14 to rats, a labeled metabolite has been isolated from the liver which has been identified by chromatographic and carrier crystallization methods as tocopheryl quinone. Evidence also has been found for the natural occurrence of trace quantities of this compound in liver and muscle extracts of mice and pigs. The presence of a second major metabolite in the tissues of these animals has been demonstrated.

Method for the assay of free and esterified tocopherols

Abstract A method for estimating the eight naturally occurring isomers of vitamin E and their esters is described. The prime feature of this method is the removal of the bulk of the lipids by low-temperature crystallization instead of saponification. The technique concomitantly affords a separation of tocopherol esters from free tocopherols. The recovery of tocopherols was superior to that obtained by the conventional saponification method, which was shown to cause extensive destruction of tocotrienols. Reduction with LiAlH 4 provided the highest yield of free tocopherols from tocopherol esters. The conjugated forms were found only in latex lipids. Analytical values are given for the tocopherols in several plant oils.

Oxidation products of α-tocopherol formed in autoxidizing methyl linoleate

The oxidation products of14C-α-tocopherol formed by heating with methyl linoleate in an air atmosphere at 60 C or 100 C were investigated. The products included a dimer, trimer and dihydroxy dimer, α-tocopherol quinone and unidentified degradation compounds. The dimer and trimer constituted the major products present after heating for 70 hr at 60 C. After 70 hr at 100 C most of the14C-α-tocopherol had been converted to degradation products; part of the14C originallt present in the 5-methyl group was recovered as14CO2 and14CH3OH.

Dimerization of α-tocopherol in vivo.

Abstract Following administration of d -α-tocopherol-C 14 to rats, a previously uncharacterized metabolite of the vitamin was isolated from the liver. This compound was shown by cochromatography and carrier crystallization to be identical to an oxidation product of α-tocopherol obtained by treatment with alkaline K 3 Fe(CN) 6 . Evidence is presented that the compound is a dimer of α-tocopherol.

On the occurrence of vitamin E in the liver of dystrophic and antioxidant-fed rabbits.

Abstract A revised procedure for the determination of α-tocopherol has been applied to the livers of rabbits in the vitamin E-deficient state and following regeneration with vitamin E or the synthetic antioxidant DPPD. No α-tocopherol could be detected in the tissues of the deficient animals or of those cured of dystrophic symptoms with DPPD. These results provide further evidence for the nonspecificity of the vitamin E requirement of animals and relegate against a possible role for tocopherols as cofactors in enzymic reactions.

Determination of N,N'-diphenyl-p-phenylenediamine in animal tissues.

Summary In connection with a study of replacement of Vit. E in vivo by certain synthetic antioxidants, liver uptake and intracellular distribution of the Vit. E-active compound N,N’- diphenyl - p - phenylenediamine (DPPD), following its administration to rats, has been determined by a method based on spectrophotometric measurement of the color developed by oxidation with ferric chloride in ethanol. Over half of the DPPD recovered was present in the soluble fraction of liver cells, one-quarter was associated with microsomes, and a small fraction recovered from mitochondria. This distribution pattern is similar to that reported for total lipids, and indicates that the intracellular location of UPPD may be passively determined by its lipid solubility. Alpha-tocopherol. on the other hand, was found predominantly in mitochondria.

The Biological Activity of Di-α-Tocopherone

Summary Di-α-tocopherone, a recently characterized metabolite of α-tocopherol isolated from animal tissues, was tested for biological activity with respect to resorption-gestation in Vit. E-deficient rats, nutritional muscular dystrophy in rabbits and hereditary muscular dystrophy in mice. The results indicate that this metabolite has less than 5% of the Vit. E activity of α-tocopherol and that it possesses no therapeutic value in treatment of the congenital myopathy. Its probable role in metabolism is that of a terminal oxidation product rather than an active form of Vit. E.