486 THE TOCOPHEROLS 



Drummond and his colleagues^* prepared very potent concentrates from 

 wheat germ oil, being the first to use selective adsorption on aluminum 

 oxide. They confirmed many of the previous observations including this 

 maximum adsorption at 2940 A. with a minimum at 2670 A. Whether it 

 was characteristic of the vitamin or of an associated substance, the band 

 "persisted" in proportion to the vitamin activity when this was destroyed 

 by ultraviolet radiation. 



Pure vitamin E was first isolated by Evans and the Emersons"* from the 

 unsaponifiable matter of wheat germ oil. By the use of cyanic acid on the 

 unsaponifiable fraction, three solid amorphous allophanates Avere obtained. 

 The alcohol regenerated from one of these, when given in a single dose of 

 3 mg., always enabled vitamin E-deficient rats to bear young. It was named 

 a-tocopherol. Of the alcohols obtained from the other two allophanates, 

 one had less biological potency (later called ^), the other none at all. a-To- 

 copherol was a light-yellow viscous oil which could not be crystallized, but 

 its conversion to another crystalline derivative (with p-nitrophenyl iso- 

 cyanate), followed by reconversion to the allophanate and regeneration of 

 the alcohol, left its biological activity unimpaired. The peak of its absorp- 

 tion band was at 2980 A., and microanalysis indicated a provisional formula, 

 C29H50O2 . Soon thereafter the same a-tocopherol was isolated from cotton 

 seed oil,^'* and later^^ still another active substance, 7-tocopherol, was ob- 

 tained from the same source. Further investigation revealed that only 

 a-tocopherol is present in lettuce and that palm oil is qualitatively similar 

 to cottonseed oil and contains no /3-tocopherol. 



In several other laboratories, tocopherols were isolated from wheat germ 

 oil, the (3 by Todd and his coworkers^^ in London, neotocopherol by Karrer 

 and his colleagues" • ^^ in Zurich, and cumotocopherol by John^^ in Got- 

 tingen, the name indicating that pseudocumohydroquinone (trimethyl- 

 hydroquinone) was produced from it by thermal decomposition. Both 

 products were probably identical with /3-tocopherol.^'' The preponderance 

 of /3-tocopherol in European wheat germ oil and of the a form in that of 

 California has not been explained. 



" J. C. Drummond, E. Singer, and R. J. MacWalter, Biochem. J. 29, 456, 2510 (1935). 



24 O. H. Emerson, G. A. Emerson, and H. M. Evans, Science 83, 421 (1936). 



25 O. H. Emerson, G. A. Emerson, A. Mohammad, and II. M. Evans, J . Biol. Chem. 

 122, 99 (1937). 



26 A. R. Todd, F. Bergel, and T. S. Work, Biochem. J. 31, 2257 (1937). 



2' P. Karrer, H. Salomon, and H. Fritzsche, Helv. Chim. Acta 20, 1422 (1937). 



28 P. Karrer and II. Salomon, Helv. Chim. Acta 21, 514 (193S). 



2'J W. John, Z. physiol. Chem. 250, 11 (1937). 



'« F. Bergo^l, A. R. Todd, and T. S. Work, ./. Chcin. Soc. 1938, 253; F. Bergol, A. 



Jacob, A. R. Todd, and T. S. Work, ibiil. 1938, 1375; F. Bergel, A. M. Copping, A. 



Jacob, A. R. Todd, and T. S. Work, ibid. 1938, 1382. 



