FACTORS ALTERING NUTRITIONAL VALUE 903 



(c) Tocopherols (Vitamins E). The tocopherols occur in varying 

 amounts in most animal and vegetable fats. Actually there are four types 

 of tocopherols which may occur in fats, namely, a-tocopherol (5,7,8- 

 trimethyltocol) , /3-tocopherol (5,8-dimethyltocol), «-tocopherol (7,8-di- 

 methyltocol) , /^-tocopherol (4,8-dimethyltocol), 7-tocopherol (7,8-di- 

 methyltocol), and 5-tocopherol (8-methyltoeol) . Tocopherol has a num- 

 ber of different functions. Probably the most important one is its func- 

 tion as vitamin E, as originally discovered by Mattill and Conklin^^'' 

 and by Evans and Bishop. -**'''*^ It was shown by these workers to be an 

 antisterility vitamin, although it was not yet identified by name (1923) 

 but was called "substance X." A second important function which can 

 be assigned to the tocopherols is their antioxidant effect. Of the four 

 tocopherols now know, the a-type has the greatest effect upon fertility, 

 and the lowest activity as an antioxidant. Conversely, 5-tocopherol is 

 the most active form as an antioxidant, and it has practically no "vitamin 

 E" activity. Table 6 summarized the tocopherol values for the common 

 vegetable oils insofar as the data are available, while Table 7 furnishes 

 corresponding information on animal fats, fish-liver oil, and dairy fats. 



An examination of Tables 6 and 7 reveals the fact that the tocopherol 

 content of most of the common vegetable oils is relatively high, and many 

 times exceeds that present in animal fats or in dairy fats. The highest 

 reported value was recorded for wheat germ oil, namely 550 mg. %, 

 while corn, cottonseed, and soybean oils are excellent sources, with tocoph- 

 erol contents varying between 80 and 168 mg. %. Olive oil is a rela- 

 tively poor source (14 mg. %), while refined coconut oil is practically 

 devoid of this vitamin (only approximately 3 mg. %). 5-Tocopherol is 

 especially abundant in corn and soybean oils. The level of tocopherols in 

 the fats is not adversely affected by hydrogenation, as evidenced by the 

 fact that the figures approximated 100 mg. % in all four samples of com- 

 mercial hydrogenated products tested. 



In the case of animal fats, most values for the tocopherols are under 5 

 mg. %. Lards and butters have been reported to contain between 1 

 and 3 mg. %, although a value of 4.2 mg. % was assigned to one sample of 

 cow's butterfat obtained in the summer. Values as high as 13 mg. % 

 have been reported for egg lipid, while cod liver oil contains 26 mg. % of 

 this vitamin. In the case of animal fat, the larger proportion of the to- 

 copherols is in the form of a-tocopherol. 



287 H. A. Mattill and R. E. Conklin, /. Biol. Chem., 44, 137-158 (1920). 



«8 H. M. Evans and K. S. Bishop, Science, 56, 650-651 (1922). 



283 H. M. Evans and K. S. Bishop, /. Metabolic Research, 3, 233-283 (1923). 



