INTRODUCTION 705 



attributed to an idontioal compound. In 1931, Olcott and Mattill-^ ap- 

 parently answered this question in (he negative; they were able to separate 

 the antisterility and antioxidant fractions of wheat germ oil by distribution 

 })etween petroleum ether and 92% methyl alcohol. Moreover, these 

 workers later showed^^ that acetylation destroyed the antioxygenic prop- 

 erty, while leaving the antisterility effect unimpaired. Finally, it was found 

 that, although the vitamin E activity and the antioxidant action occurred 

 in a number of vegetable oils, such as lettuce, tomato, corn, cottonseed, 

 soybean, carrot, alfalfa, palm, and peanut, variations in the two effects 

 were to be notetl in the case of yeast fat, lard, cod liver oil, and castor oil. 

 However, these earlier experiments were later found to be incorrect when 

 more concentrated sources of the vitamin E were available for study. The 

 relationship between the antisterilitj^ and antioxidant effects could not be 

 finally clarified until the chemical nature of the several compounds having 

 vitamin E activity was worked out. 



The chemical nature of vitamin E has been elucidated by a brilliant series 

 of investigations which have culminated in the synthesis of several of these 

 compounds. As early as 1927, Evans and Burr^" proved that vitamin E is a 

 constituent of the non-saponifiable fraction of fats. Olcott and MattilP^--^ 

 prepared concentrates of high potency by vacuum distillation, while Drum- 

 mond et al.^^ employed chromatographic adsorption on Brockmann alumina. 

 The first clear-cut separation of piu'e ciystallized esters resulted from the 

 work of Evans, Emerson, and Emerson,^^ -^yj^Q were able to prepare two 

 different allophanates w-hich showed biological activity. The ester having 

 the higher activity was designated as a-tocopherol {roKoa, childbirth; (pepeiv 

 to bear; ol, indicating an alcohol). The presence of an alcoholic group in 

 vitamin E was first demonstrated by Olcott^' and by Drummond and 

 associates'^; this was definitely proved when crystalline esters were pre- 

 pared. 



It soon became evident that there are several tocopherols w^hich possess 

 varying degrees of biopotency. The allophanate prepared by Evans et al.,^- 

 melting at 136-138°C., w^as subsequently further purified by recrystalliza- 

 tion from acetone (m.p., 144-146°C.)''* and w^as shown to have a lower 

 activity than a-tocopherol ; Emerson et al.^^ designated it as j8-tocopherol. 

 A third allophanate was prepared from cottonseed oil and was designated as 

 7-tocopherol.'^ This also was found to have a biological activity only one- 



28 H. S. Olcott and H. A. Mattill, /. Biol. Chem., 93, 59-64, 65-70 (1931). 



M H. S. Olcott and H. A. Mattill, J. Biol. Chem., 104, 423-435 (1934). 



^0 H. M. Evans and G. O. Burr, Mem. Univ. Calif., 8, 1-158 (1927). 



" J. C. Drummond, E. Singer, and R. J. Mac Walter, Biochem. J., 29, 456-471 (1935). 



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

 (1936). 



" ir. S. Olcott, J. Biol. Chem., 110, G95-701 (1935). 



'^ O. H. Emerson, G. A. Emerson, A. Mohammad, and H. M. Evans, J. Biol. Chem., 

 122, 99-107 (1938). 



