684 



XI. VITAMINS E (tocopherols) 



Ward* are responsible for the discovery of the fifth member of the group — 

 c-tocopherol — in wheat germ oil. Green and co-workers,^ using the so- 

 called two-dimensional chromatography, were not only able to separate 

 and identify the several known tocopherols, including e-tocopherol, but 

 they also succeeded in provdng the presence of f-tocopherol in a number of 

 natural sources. At the time of writing this manuscript, word has just 

 been received of the possible discovery of the final possible member of the 

 tocopherol series, which will presumably be known as ?7-tocopherol, in 

 Japanese rice. According to the generally accepted usage,^ the tocopherols 

 are defined as monomethyl, dimethyl or trimethyl derivatives of tocol as 

 follows (Fig. 1): 



CH2 



^°yV>cH2 



# * * 



vA^/C - (<^"2)3-C^ -(CHs^s-CH- (CH2)jCH - CH3 



CH3 CH3 CH3 CH3 



a -TOCOPHEROL : 

 /3 -TOCOPHEROL 

 v^-TOCOPHEROL 

 <j -TOCOPHEROL 

 £ -TOCOPHEROL 

 ^-TOCOPHEROL 



5.7,8 - TRIMETHYL-TOCOL 



5,8 - DIMETHYL -TOCOL 



7,8 - DIMETHYL -TOCOL 



8 - METHYL - TOCOL 



5 - METHYL- TOCOL 



5.7 - DIMETHYL- TOCOL 



Fig. 1. Structure of different tocopherols (vitamins E).^ 



The newly-discovered ?7-tocopherol, which represents the only possible 

 remaining methyl derivative, would thus be 7-methyl-tocol. 



2. Historical Development 



The first indication that a third fat-soluble \'itamiii existed, in addition 

 to vitamins A and D, was evident from the results of Evans and Bishop^"^' 



* P. W. R. Eggitt and L. D. Ward, J. Sci. Food Agr., 4, 569-579 (1953). 



5 J. Green, S. Marcinkiewicz, and P. R. Watt, J. Set. Food Agr., 6, 274-282 (1955). 



* H. R. Bolinger and M. L. Bolinger-Qviaife, Analytical Methods and Their Use in the 

 Evaluation of Vitamin E., Proc. Third Intern. Congr. on Vitamin E, Venice, Sept., 1955. 

 Valdonega, Verona, 1956, pp. 30-45 



' H. M. Evans and K. S. Bishop, Science, 56, 650-G51 (1922). 



» H. M. Evans and K. S. Bishop, Am. J. Physiol., 63, 396-397 (1922). 



9 H. M. Evans and K. S. Bishop, J. Am. Med. Assoc, 81, 889-892 (1923). 

 10 H. M. Evans and K. S. Bishop, J. Metabolic Research, 1, 319-333, 335-356 (1922). 

 1' H. M. Evans and K. S. Bishop, J. Metabolic Research, 3, 201-231, 233-316 (1923). 



