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Relative Activity of D- and DL--Tocopheryl Acetate Based on Plasma Levels

Hoffmann-La Roche Inc., Nutley, New Jersey

Abstract

D- and dl--tocopheryl acetate were compared in three species (calf, rat, chick) using three modes of administration (single intramuscular injection, single or multiple oral doses and feeding in the ration) and three carriers (water base emulsion, olive oil solution and dry commercial products). D- and dl--tocopheryl acetate were administered in all trials on an equivalent I.U. basis using the accepted conversion of 1 mg. of d- being equal to 1.36 mg. of dl--tocopheryl acetate.

Relative performance was based on plasma tocopherol concentrations determined up to 21 days post administration in calves; 56 days in rats and 28 days in chicks.

In calves, intramuscular administration of a water base emulsion was more effective than either a single oral or daily oral dose of dry products.

In rats, intramuscular injection of the same water base emulsion was more effective than a single oral dose given in olive oil. Continuous supplementation of the ration with the dry products appeared equal to the intramuscular administration based on relative plasma tocopherol concentrations at three and four weeks, respectively.

In chicks, intramuscular injection of the water base emulsion was more effective than the equivalent single dose given orally in oil solution based on rate of decline in the plasma.

In all three species, under all conditions of administration, with all three carriers, respective plasma tocopherol concentrations were equal for d- and dl--tocopheryl acetate when both were administered on an equal I.U. basis. These data thus confirm the accepted ratio of 1.36 I.U. of vitamin E activity for 1 mg. of d--tocopheryl acetate compared to 1.0 I.U. of activity for 1.0 mg. of dl--tocopheryl acetate.

¹ The authors wish to acknowledge the assistance of Miss Ann Dowell in performing the plasma tocopherol determinations and Dr. R. E. White in conducting statistical analyses.