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The chemical estimation of vitamin‐E activity in cereal products. IV. —ϵ‐tocopherol
Author(s) -
Eggitt P. W. Russell,
Norris F. W.
Publication year - 1956
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740070706
Subject(s) - tocopherol , chemistry , quinone , reagent , vitamin e , chloroform , nitric acid , absorption (acoustics) , organic chemistry , absorption spectroscopy , chromatography , antioxidant , materials science , quantum mechanics , composite material , physics
ϵ‐Tocopherol has been isolated from wheat bran and some of its properties and its reactions have been studied. Its absorption spectrum, and that of nitroso‐ϵ‐tocopherol, are almost identical with the corresponding spectra for β‐tocopherol. ϵ‐Tocopherol, when oxidized with the Emmerie‐Engel reagents, yields a tocopheroxide, which may be converted into the isomeric ϵ‐tocopherylquinone. The latter shares a characteristically shaped absorption spectrum with β‐tocopherylquinone. With nitric acid in ethanol ϵ‐tocopherol forms a red o ‐quinone and other products with a reaction spectrum again very like that for β‐tocopherol. Only the β‐ and ϵ‐homologues produce a brilliant violet unstable colour (not the quinone) with nitric acid in chloroform. In these reactions the new tocopherol behaves as if it is 5‐methyltocol and this structure is confirmed by the fact that ϵ‐tocopherol yields 5: 7‐dimethyltocol (ζ‐tocopherol) under conditions that convert β‐tocopherol to α‐tocopherol. Difficulties encountered in applying the Quaife rdtrosation technique to the tocopherols are discussed. The factor converting depth of colour to concentration when ϵ‐tocopherol is assayed by the modified Emmerie‐Engel method described previously 1, 2 is 96.