METABOLISM OF CAROTENOIDS AND VITAMINS A 567 



any experiment was 226 I.U./g. yolk; this value was found in one egg from 

 a hen in Group 8. The carotenoids Avcie reduced in the egg yolk from a 

 normal value of about 38 ng./g. to a minimum value of 8.4 /ig-/g- No 

 effects which could not be attributed to seasonal changes were observable 

 until as much as 15,000 I.U. of vitamin A was added as a supplement for 

 each pound of food. 



a. The Effect of Incubation on the Carotenoids and Vitamin A in Eggs. 

 It was found by Parrish ef al.'*-'' that the percentage of vitamin A in ester 

 form in the yolk increased during incubation, and that the vitamin A in the 

 embryo liver was predominantly in the ester form, the proportion in the 

 liver being higher than that in the yolk. 



Parrish and co-workers^-"* reported also that the embryo in eggs from 

 hens receiving 12,000 I.U. vitamin A/lb. food assimilated vitamin A ex- 

 ponentially throughout the period of incubation, while this occurred only 

 until the eighteenth to twenty-first day, or the twelfth to eighteenth day, 

 when the eggs were from hens receiving 3000 or 1800 I.U. vitamin A/lb., 

 respectively. In the intermediate group (3000 I.U./lb.) at the time of 

 hatching, 28% of the original vitamin A in the incubated egg was present 

 in the yolk-free embryo, 45% was in the unabsorbed yolk, and the balance 

 was lost. A similar loss of vitamin A occurred when infertile eggs were in- 

 cubated. Neither the carotenes^^^ nor the xanthophylls^"^ in the yolk were 

 metabolized during incubation. When the chicks were hatched, the livers 

 contained only about 8% of the total body carotenoids. 



(7) Antivitamin A 



Meunier and associates^^^-^^^* prepared an oxidation derivative of vita- 

 min A (Substance Z) which acts as an antivitamin, and hence is called "an- 

 tivitamin A." In this compound, one of the double bonds on the side 

 chain is believed to be hydroxylated. It is produced when /3-carotene or 

 vitamin A is oxidized with vanadium tetroxide (V204).^--~^22b Retinenei 

 is formed as an intermediate product. Meunier^'--^ proposed two possible 

 formulae for antivitamin A, as given below: 



^^ D. B. Parrish, R. N. Williams, and P. E. Sanford, Arch. Biochem., 34, 64-66 

 (1951). 



920'' D. B. Parrish, R. N. Williams, and L. F. Payne, Arch. Biochem., 29, 1-6 (1950). 



9" P. Suomalainen, Soumen Kemistilehti, 12 B, 30 (1939); Chem. Abst., 34, 145 

 (1940). 



922 P. Meunier, J. Jouanneteau, and R. Ferrando, Compt. rend., 230, 140-142 (1950). 



922a P. Meunier, Fortschr. Chem. org. Naturstoffe, 9, 88-113 (1952). 



922b p Meunier, G. Zmngelstein, J. Jouanneteau, and R. Mallein Compt. rend. 230, 

 1323-1324 (1950). 



