430 IX. CAROTENOIDS AND VITAMINS A 



high concentration of this chromogen in the fat of a woman suffering from 

 jamidice. The presence of lutein has hkewise been noted in milk and 

 butter/* in the serum of cattle/^ in chicken fat,^^ and in egg yolk.^'^ Lutein 

 has likewise been observed as a pigment in the feathers of the wild Madeira 

 canary {Serinus canarius) and of the yellow-hammer (Emberizia ciirinella)?'^ 

 Zechmeister and Tuzson" also recorded the occurrence of this carotenol 

 in the green water-frog {Rana escidenla). The presence of zeaxanthin has 

 been recorded in most of the sources in which lutein has been observed, 

 including human fat,-^-**^ human liver,^^ hen's egg,"'*-''^'" in the egg of the 

 Atlantic spiny dogfish {Squalus acanthius) ,''^ as well as in the feathers of 

 the wild canary {Serinus canarius)'''^ and in the green water-frogJ^ Zech- 

 meister and Tuzson''^ observed the presence of another oxy-carotenoid, 

 capsanthin, in human fat. It is considered that the presence of this chro- 

 mogen under these conditions is adventitious; presumably it occurs in the 

 fat of Hungarian peasants, chiefly as a result of their high consumption of 

 paprika.^* The latter is the principal natural source of capsanthin. Al- 

 though a wide variety of the cis- and fraws-isomers of the several carotenoids 

 which are provitamins A, may also serve as a source of vitamin A/^ there 

 is no direct evidence that these carotenoids may be absorbed as such. 

 However, it seems quite reasonable to the author that this transformation 

 of the molecule need not preclude the absorption of such compounds. 



In the preceding discussion, evidence was adduced for the absorption of 

 many carotenoids simply by demonstrating that these carotenoids have 

 been isolated from animal or human tissues. The acceptance of the evi- 

 dence, at least as regards the higher animals, must predicate a failure of 

 synthesis of the carotenoids in situ. There is no evidence for this synthesis, 

 especially in the case of those carotenoids which serve as provitamins A. 

 In the absence of synthesis, the only other explanation is that they have 

 gained entrance to the body by absorption from the gastrointestinal tract. 

 Unfortunately, the data furnish no precise values as to the rate of absorp- 

 tion. For a further discussion of the absorption of carotene and of the 

 related carotenoids, the reader is referred to The Lipids, Vol. II, pages 

 282-300. 



" A. E. Gillam, I. M. Heilbron, R. A. Morton, G. Bishop, and J. C. Drummond, 



Biochem. J., 27, 878-888 (1933). 



'■> H. Brockmann and O. Volker, Z. physiol. Chem., 224, 193-215 (1934). 



'6 L. Zechmeister and P. Tiizson, Z. -physiol. Chem., 238, 197-203 (1936). 



'« R. Kuhn, A. Winterstein, and E. Lederer, Z. physiol. Chem., 197, 141-160 (1931). 



'''' H. H. Strain, Chromatographic Adsorption Analysis, Interscience, New York, 

 London, 1945. 



'8 H. V. Euler and U. Gard, Arkiv Kemi Mineral. Geol., B 10, No. 19, 1-6 (1931). 



'^ L. Zechmeister, Vitamins and Hormones, 7, 57-81 (1949). 



