Stereoisomers of alpha-tocopheryl acetate. III. Simultaneous determination of resorption-gestation and myopathy in rats as a means of evaluating biopotency ratios of all-rac- and RRR-alpha-tocopheryl acetate.

The resorption-gestation test furnishes information on a more complex vitamin activity than is the case with other vitamin E tests, so that correspondingly more importance attaches to the results. A drawback is their questionable validity for species other than the small rodents in which fetal resorption has so far been observed. In the four experiments carried out, RRR-alpha-tocopheryl acetate (alpha-TA) was compared with all-rac-alpha-TA (USP standard) and a mean relative activity of 1.32 was determined. The additional measurement of pyruvate kinase (PK) activity serves to emphasize the correlation with nutrition-linked myopathy. This biochemical lesion is seen in various animal species and man. In two experiments, the parameters fetal resorption and plasma PK activity were measured together. For all-rac-alpha-TA and RRR-alpha-TA, the following activity ratios were calculated: Resorption-gestation 1:1.35; Myopathy 1:1.47. It could be shown that the two parameters are measurable quantitatively in a single experimental set-up and that the results are in good agreement. The accepted activity of 1 mg RRR-alpha-TA = 1.36 USP Units was fully confirmed.