504 THE TOCOPHEROLS 



sulfhydiyl groups,^^ and crude sources of vitamin B complex^" are known 

 to be effective in other systems. Complications are increased by the factor 

 of actual and relative concentrations; in more than minimal amounts, caro- 

 tene becomes a pro-oxidant,^^"^^ and there is an optimum concentration of 

 tocopherol for most effective stabilization.^^' ^^ 



The deterioration of fats and oils in natural and prepared foods and its 

 prevention by tocopherols and synergists are, chemically, still in the em- 

 pirical stage.^^ In general, the most effective fat antioxidants have a normal 

 oxidation potential between 848 and 484 millivolts.^' A difference in po- 

 tential must exist between antioxidant and synergist, and the oxidation of 

 the synergist by the oxidized form of the antioxidant must be faster than 

 the oxidation of the antioxidant by the fat peroxides, which, in turn, must 

 be faster than the oxidation of the synergist by the fat peroxides. 



D. SPARING ACTION ON VITAMIN A 



Closely allied to the antioxygenic action of the tocopherols is their long- 

 discussed sparing action on vitamin A. The first indications of this physio- 

 logical property were the observations of Moore^* and of Bacharach^^ to the 

 effect that the vitamin A reserves in the livers of rats kept for a long time 

 on E-deficient diets were much lower than those of rats receiving supple- 

 ments of vitamin E. Tocopherol concentrates prevented the autoxidation 

 of carotene in vitro and increased the biological response of vitamin A-de- 

 ficient rats to minimal quantities of carotene.^'' The vitamin A requirement 

 is thus partly dependent on the adequacy of dietary vitamin E. 



Studies by Hickman and his colleagues'*^ showed that the growth-pro- 

 moting action of vitamin A and of carotene in rats was equally enhanced 

 by the simultaneous oral administration of any of the tocopherols; in hu- 

 man subjects fecal excretion of added dietary carotene and of other re- 

 ducing materials was increased when tocopherols or tocoquinones were also 



29 P. Gyorgy, E. T. Stiller, and M. B. Williamson, Science 98, 518 (19-13). 



30 R. Tomarelli and P. Gyorgy, /. Biol. Chem. 161, 367 (1945). 



31 C. R. Thompson and H. Steenbock, Arch. Biochem. 4, 15 (1944). 



32 H. O. Kunkel and W. L. Nelson, /. Biol. Chem. 183, 149 (1950). 



33 E. Heftmann, /. Am. Oil Chemists' Soc. 24, 404 (1947). 



34 C. E. Swift, W. G. Rose, and G. S. Jamieson, 0^7 & Soap 19, 176 (1942). 

 36 C. Golumbic, Oil & Soap 20, 105 (1943). 



3^ Deterioration of Fats and Oils, Quartermaster Corps Manual No. 17-7. Commit- 

 tee on Food Research, Chicago, 1945. 

 3' C. Golumbic, Oil & Soap 23, 184 (1946). 



38 T. Moore, Biochem. J. 34, 1321 (1940). 



39 A..L. Bacharach, Quart. J. Pharm. Pharmacol. 13, 138 (1940). 



*" F. W. Quackenbush, R. P. Cox, and H. Steenbock, /. Biol. Chem. 145, 169 (1942). 

 " K. CD. Hickman, M. W. Kaley, and P. L. Harris, ./. Biol. Chem. 152, 303, 313, 321 

 (1944). 



