Biological Potency of Zeta-Tocopherol

Abstract

ζ-TOCOPHEROL was first isolated from cereal grains by Green, Marcinkiewicz and Watt¹, and was shown to be identical (apart from the presumed difference between the natural optically active and the synthetic racemic forms) with 5 : 7-dimethyltocol, synthesized many years previously by Karrer and Fritsche² and by Bergel, Copping, Jacob, Todd and Work³. The latter two groups of workers, in a series of papers, disputed the biological potency of 5 : 7-dimethyltocol. Karrer and his co-workers^4,5 stated that the substance had similar activity to β-tocopherol (that is, 30–50 per cent of the potency of α-tocopherol) whereas the British workers⁶ maintained that 5 : 7-dimethyltocol had the same potency as α-tocopherol. Both groups used the rat anti-sterility assay as a measure of biological activity. Since ζ-tocopherol is an appreciable constituent of the tocopherol complex in cereals (for example, 44 per cent of the total tocopherols in barley), it is important that its potency, relative to α-tocopherol, be known.