Biopotency of alpha-tocopherols as determined by curative myopathy bioassay in the rat.

The decrease in plasma pyruvate kinase activity after administration of various tocopherols to vitamin E-deficient rats provided the basis for a 3-point parallel-slope assay for vitamin E activity. Based on 6 replicate assays, RRR-alpha-tocopheryl acetate (RRR-alpha-TA) was 141% as active as all-rac-alpha-tocopheryl acetate (all-rac-alpha-TA). This confirms many previous reports with other bioassays and is in agreement with the unit-weight relationships assigned by The National Formulary. 2-ambo-alpha-Tocopheryl acetate was 97% as active as all-rac-alpha-TA indicating that only the configuration of the 2-position on the chromanol ring is important in determining the biological activity of alpha-tocopherol.