692 XI. VITAMINS E (tocopherols) 



to have a tocopherol content of only 2 mg. %, 75 while Kofler^^ cites the 

 value for tocopherol in beef tallow as 1 mg. %. In the case of butter, the 

 results of numerous assays have shown figm'es varying between 1.7 and 

 4.2 mg. %."~^^ Lard is reported to have similar low values ;'^^''^ Harris 

 et alP observed a total tocopherol content in one sample of lard of 2.7 mg. 

 %, of which 2.3 mg. was found to be a-tocopherol and <0.4 mg. % con- 

 sisted of 7-tocopherol. Lange^^ compiled an exceedingly comprehensive 

 and useful report of the tocopherol content of a large number of animal 

 and vegetable fats, as well as of other tissues. 



The amount of tocopherols present in animal fats is directly related to 

 the amount taken in the diet. Barnes, Lundberg, Hanson, and Burr^'- 

 suggested that the antioxidants responsible for the normal stability of 

 body fat in the rat are entirely of dietary origin, and consist solely of 

 vitamins E. Thus, it was shown that when rats were raised from the time 

 of weaning to 100 days of age on a diet containing no vitamin E or fat, their 

 rendered body fats Avere abnormally susceptible to oxidation by atmos- 

 pheric oxygen at the C=C linkages. The oxygen absorption measure- 

 ments at 100°C. were characterized by an almost complete absence of an 

 induction period. When the rats on the vitamin E-free diet were given a 

 single dose of 200 mg. of a-tocopherol in the diet before they were sacri- 

 ficed, the stability of the body fats was restored. In a later study by this 

 group, Lundberg et alP found that the maximum deposition of a-tocopherol 

 was not achieved in the rat until seven to ten days after the feeding of a 

 single 50 mg. dose. The concentration of tocopherol decreased slowly 

 thereafter if no additional quantities were given ; the level reached about 

 one-half of the maximum value after two months. On the other hand, 

 when varying amounts of a-tocopherol up to 500 mg. were given in single 

 doses, increasing amounts were noted in the abdominal fats. Under such 

 conditions, the fat depots may become the major sites of storage of vitamin 



" M. Kofler, Helv. Chim. Acta, 26, 2166-2176 (1943). 

 " M. L. Quaife, J. Biol. Chem., 169, 513-514 (1947). 



•'s A. Emmerie and C. Engel, Z. Vitaminforsch., IS, 259-266 (1943); Chem. Zentr., 

 1943, 11, 1974. Also cited by \V. Lange, J. Am. Oil Chemists' Soc, 27, 414-422 (1950). 

 " P. L. Harris, M. L. Quaife, and W. J. Swanson, J. Nutrition, 40, 367-381 (1950). 



80 P. L. Harris, W. J. Swanson, and K. C. D. Hickman, /. Nutrition, 33, 411-427 

 (1947). 



81 H. Lieck and H. Willstaedt, Svensk Kern. Tid., 57, 134-139 (1945); Chem. AhsL, 40, 

 4759(1946). 



82 R. H. Barnes, W. O. Lundberg, H. T. Hanson, and G. O. Burr, J. Biol. Chem., 149, 

 313-322 (1943). 



83 W. O. Lundberg, R. H. Barnes, 'SI. Clausen, and G. O. Burr, /. Biol. Chem., 153, 

 265-274 (1944). 



