286 ESSENTIAL FATTY ACIDS 



or nordihydroguaiaretic acid,-^ substances that have antioxidant action. 

 Conversely, feeding oxidized fat to animals has toxic effects. 



These various observations suggest a possible antioxidant action for 

 tocopherol in sparing metabolic unsaturated acids. Hickman^- has suggested 

 that perhaps a balance of pro-oxidants and antioxidants is maintained in 

 tissue to insure the proper metabolism of such substances as essential fatty 

 acids, that a ''pro-oxidant condition" would promote oxidation and that an 

 "antioxidant condition" would protect the acids against oxidation. In recent 

 experiments testing this hypothesis some unexpected results were ob- 

 tained.-® The conversions of linoleic and linolenic acids to more unsaturated 

 acids by fat-deficient rats were used as measures of utilization of these 

 substances, when they were administered either alone or in combination 

 with benzoyl peroxide (pro-oxidant) or tocopherol. Best growth response 

 and greatest synthesis of body fat was obtained with supplements of benzoyl 

 peroxide plus linoleate, and least with benzoyl peroxide alone. The toxic 

 effect of benzoyl peroxide was thus reversed when fed with linoleate. The 

 synthesis of arachidonate from linoleate or linolenate was unaffected by 

 either benzoyl peroxide or tocopherol. Benzoyl peroxide increased the 

 formation of hexaenoate from linoleate but not from linolenate. Thus it 

 will be seen that the matter of relationship between tocopherol and essential 

 fatty acids is at present rather confused. 



The riboflavin requirement for normal growth of rats has been found 

 to be increased when cottonseed oil is incorporated in the diet at a mod- 

 erately high level .^^ Although the effect of the oil on intestinal flora may 

 be a cause of the diminished growth, an alternate explanation may be that 

 riboflavin is involved in the metabolism of unsaturated acids. Riboflavin 

 is a constituent of the enzyme which causes the reduction of cytochrome c,^^ 

 and cytochrome c is an essential component of the enzyme system which 

 oxidizes saturated fatty acids.^' Thus, an increased metabolism of fat may 

 require an increased amount of riboflavin. 



VI. Estimation 



RALPH T. HOLM AN 



A. SPECTROPHOTOMETRIC ANALYSIS 



Observations by Dann and Moore^ that prolonged saponification of oils 

 increases their ultraviolet light absorption has led to a spectrophotometric 



26 H. Granados, E. Aaes-Jorgensen, and H. Dam, Brit. J. Nutrition 3, 322 (1949). 



26 p. W. Witten and R. T. Holman, Arch. Biochem. and Biophys. 37, 90 (1952). 



27 R. Reiser and P. B. Pearson, J. Nutrition 38, 247 (1949). 



28 A. L. Lehninger and E. P. Kennedy, /. Biol. Chem. 173, 753 (1948). 



29 E. Haas, B. L. Horecker, and T. R. Hogness, /. Biol. Chem. 136, 747 (1940). 

 1 W. J. Dann and T. Moore, Biochem. J. 27, 1166 (1933). 



