44 VITAMINS A AND CAROTENES 



oils. Even samples of synthetic vitamin A contain neovitamin A.^®^ Table 

 XI shows the occurrence of neovitamin A in some fish liver oils, concen- 

 trates, distillates, and synthetic vitamin A. 



The neovitamin A was purified by Robeson and Baxter' ^^ y[^ [iq p. 

 phenylazobenzoate (m.p. 94 to 96°) which was saponified and the vitamin 

 regenerated and crystallized from ethyl formate at —70° (m.p. 58 to 60°). 

 The neovitamin A anthraquinone iS-carboxylate was also prepared (m.p, 

 134 to 136°) and found to be red as contrasted with the corresponding ester 

 of the a\\-trans isomer, which is yellow. Neovitamin A has a well-defined 

 maximum in the ultraviolet at 328 m/x, with an £'}^ni. value in isopropanol 



TABLE XI 

 Occurrence of Neovitamin A in Fish Liver Oils and Synthetic Vitamin A 



Preparations 



Neovitamin A, 

 in % of total 

 Sample vitamin A References 



U. S. Reference Cod Liver Oil No. 3 



Dogfish liver oil 



Soupfin shark liver oil 



Halibut liver oil 



California jewfish liver oil 



Spanish red tuna liver oil 



Distillate from dogfish liver oil 



Distillate from soupfin shark liver oil 



Unsaponifiable matter from soupfin shark distillate 



Distilled vitamin A concentrates 



Synthetic vitamin A 



of 1673 (cf. ref. 165). The infrared spectra of the two stereoisomers are al- 

 most identical. 



Chemically neovitamin A is more stable to air oxidation, slightly less 

 strongly adsorbed on weakened alumina (5% water), and forms anhydro- 

 vitamin A more slowly than the all-^rans isomer. Maleic anhydride reacts 

 rapidly with the all-/rans vitamin A to form an adduct which fails to give 

 the Carr-Price test,^^ whereas neovitamin A reacts at a much slower rate. 

 For example, after treatment of neovitamin A palmitate and vitamin Ai 

 palmitate with maleic anhydride in benzene for 16 hours, 90 % of the former 

 and only 5 % of the latter were recovered unchanged as measiu'ed ])y the 

 antimony trichloride color test. This method has been adopted for the as- 

 saying of neovitamin A in the presence of vitamin Ai.'^^''^^ 



'" J. D. Cawley, C. D. Robeson, L. Weisler, E. M. Shantz, N. D. Embree, and J. G. 



Baxter, Science 107, 346 (1948). 

 !"■' P. Meunier and J. Jouanneteau, Bull. soc. chim. biol. 30, 260 (1948). 

 185 P. D. Dalvi and R. A. Morton, Biochem. J. 50, 43 (1952). 



