PROPERTIES OF VITAMINS A AND RELATED COMPOUNDS 733 



concentration A2 _ E (693 m/u) 



concentration A, 1 



h (620 m^) — - I- ("••3 ni^) 



This overcomes the criticism of Lederer and Hutlimann'^' as to the inac- 

 curacy of determininjj; ^•itamin A-j simply on the basis of the ratio of E 

 (693 van) to E (020 m/x) without correction of the 020 m/x value to allow for 

 the effect of vitamin A2. Lederer, Verrier, Glaser, and Hiittier^" have 

 shown that the natural color test inhibitors found in fatty acids cause a 

 decreased absorption at 093 m/x withotit affecting the band at 645 m/x 

 appreciably. However, the latter band may be displaced to 635 or 655 m)u. 

 Oxidation of the oil also lowers the 693 mjj. band without affecting the (545 

 van band ; the intensity of the 693 m/x band reappears later in full intensity. 

 Morton" therefore recommends the application of the Carr-Priee proce- 

 dure for the determination of vitamin Ao only when the non-saponifiable 

 extracts are used. Although the carotenoids also react with antimony 

 trichloride, the maximum value is considerably below that of vitamin Ai, 

 being at 590 van- In determining the presence of vitamin A in a mixture of 

 vitamin A and carotenoids, a correction for the E (620 m/x) value can be 

 made for carotene, based upon the colorimetric determination of this 

 chromogen. 



{5) Related Compounds Formed, by Action of Acids on Vitamin A 



Althotigh the vitamins A are relatively stable toward alkalies, they are 

 quite susceptible to inorganic acids. Because such acids develop a color 

 with vitamin A, it has been proposed to use this reaction as a method for 

 determining vitamin A.^^^ Thus, stilfuric acid, phosphoric acid,^^^ chloric 

 acid,-^" molybdenum phosphotungstic acid,^^' and trichloroacetic acid^^^ 

 have all been employed. They are sometimes used alone or in combina- 

 tion with a phenol. 



a. Anhydrovitamin A. When \itamin A is treated with mineral acids, 

 a transformation in the molecule results which is associated with a change 

 in absorption spectrum.^^''^^-'*^-^'*^ The resulting product has been referred 

 to as "spurious vitamin A," "cyclized" vitamin A, and anhydrovitamin 

 \ 128.244 Undoubtedly, the last designation is the most appropriate. 



"' E. Lederer, M. L. ^'prrier, R. Glaser, and M. C. Hiittier, Bull. soc. chhn. hiol.. 21, 

 629-648 (1939). 



-'* H. R. Rosenberg, Chemistrij and Phiiftiologii of the Vitnmins. Interscience, New York, 

 1942. 



"9 E. Kobayashi and K. Yamamoto, J. Soc. Chem. I mi. Japan, 27, 1060-1067 (1924). 

 Cited bj' H. R. Rosenberg, Chemistry and Physiology of the Vitamins, p. 80. 



2« A. E. Pacini and M. H. Taras, J. Am. Phann. Assoc, 26, 721-723 (1937). 



"1 N. Bezssonoff, Bull. soc. chim. biol., 11, 294-307 (1929). 



2« W. R. Fearon, Biochem. J., 19, 888-895 (1925). 



"3 D. C. Castle, A. E. Gillam, I. M. Heiibron, and H. W. Thompson, Biochem. J., 28, 

 1702-1711 (1934). 



=" N. D. Embree. J. Biol. Chem., 128, 187-198 (1939). 



