CHAPTER XI 



THE METABOLISM AND NUTRITIONAL 



VALUE OF THE VITAMINS E 



(TOCOPHEROLS) 



1. Introduction 



As in the case of many biologically important compounds, vitamin E 

 serves several different functions in the animal. It is active as an anti- 

 sterihty vitamin, and it may also act as an antioxidant to prevent the oxida- 

 tion of fats. We now know that, although the same vitamin E can me- 

 diate several physiologic activities, different members of the group act 

 most efficiently in aiding each of the several functions attributed to this 

 vitamin. 



It is now generally believed that there are seven members of the vitamin 

 E group, all of which have the chroman ring, but which differ in the num- 

 ber and position of the side chains attached to it. In the original separa- 

 tion (in 1936) by Evans, Emerson, and Emerson,' of the members of the 

 group which were biologically active, the a-tocopherol was separated as a 

 crystalline allophanate. Two years later, this group prepared a second 

 and third active principle from wheat germ and cottonseed oil, which 

 were designated /3- and a-tocopherol.- 



Subsequently, the fourth member of the group was discovered, in 1947, 

 by Stern and co-workers,* and was called 5-tocopherol. It was found to 

 possess a greater antioxidant activity than that possessed by the members 

 of the group which were discovered earlier. On the other hand, the anti- 

 sterihty action of this newest member was found to be the weakest of that 

 present in any of the four vitamin E compounds then knowQ. Eggitt and 



1 H. M. Evans, O. H. Emerson, and G. A. Emerson, /. Biol. Chem., 113, 319-332 

 (1936). 



2 O. H. Emerson, G. A. Emerson, A. Mohammad, and H. M. Evans, /. Biol. Chem., 

 122, 99-107 (1938). 



3 M. Stern, C. D. Robeson, L. Weisler, and J. G. Baxter, /. Am. Chem. Soc, 69, 869- 

 874 (1947). 



683 



