PROPERTIES OF THE TOCOPHEROLS 



817 



\'itamin A and /3-carotene.^^ The sparing action of natural tocopherol 

 concentrates on the utilization of carotene and vitamin A in vivo has been 

 demonstrated by Hickman, Kaley, and Harris. ^^^"^"^ The relative position 

 of the 7", j8-, and a-tocopherols as antioxidants is the same as that demon- 

 strated by Olcott and Emerson^*'^ and by Hove and Hove/"* using markedly 

 different systems. A typical result obtained when vitamin A acetate was 



TIME, H r. 



Fig. 6. The relative activity of 0.1% tocopherols as antio.xidants for vitamin A acetate 

 in olive oil (50,000 U.S.P. unit.'^ per gram) at 39°C.35 



employed as the test substance is shown in Figure 6. The relative effective- 

 ness of the a-, /3-, 7-, and 5-tocopherols expressed as percentage increase in 

 induction period over unprotected blanks was found to be 1:1.3:1.8:2.7, 

 respectively, at 39°C., and 1:1.1: 1.6: 1.7 at oo^C.^^ 



Another property closely associated with the antioxidant activity of 

 tocopherol is the resistance to oxidation. Stern and associates'^ have com- 

 pared this property by determining the amount of the several tocopherols 



">* K. r. D. Hickman, M. W. Kalev, and P. L. Harris, J. Biol. Chem., 152, 303-311 

 (1944). 



i« P. L. Harris, M. W. Kalev, and K. C. D. Hickman, J. Biol. Chem., 152, 313-320 

 (1944). 



»<» K. C. D. Hickman, M. W. Kalev, and P. L. Harris, J. Biol. Chem., 152, 321-328 

 (1944). 



">' H. S. Olcott and O. H. Emerson, J. Am. Chem. Soc, 59, 1008-1009 (1937). 



'»» E. L. Hove and Z. Hove, /. Biol. Chem., 156, 611-621, 623-632 (1944). 



