DIGESTION, ETC. OF CAROTENOIDS IN THE G.I. TRACT 295 



of /3-carotene, the theoretical proportion of vitamin A formed would be 

 48.6% of that of a corresponding amount of /3-carotene, if one assumes 

 that the latter compound yields two molecules of vitamin A. The ab- 

 sorption of cryptoxanthin is likewise proved by the fact that it is changed 

 to vitamin A in the wall of the intestine in the case of the rat 3 ' 16 and of the 

 chicken. 307 



(b) Lutein. Two isomeric dihydroxycarotenoids, known also as xantho- 

 phylls, which are widely distributed in nature, have the empirical formula, 

 C 4 oH 5 4(OH) 2 . These carotenols are lutein and zeaxanthin. They fre- 

 quently occur in mixtures in natural products, but they can be readily 

 separated from each other by modern chromatographic technics. 



The presence of lutein in the tissues and excretion products constitutes 

 our main proof of its absorbability. As in the case of the other caro- 

 tenoids, its occurrence under such conditions is the result of its presence 

 in the food. Lutein has been reported in human fat, 295,308 in the livers 

 obtained post mortem from men considered to be normal, 298 or from patients 

 who had died from a variety of diseases. 297 The presence of this carotenol 

 has likewise been demonstrated in human skin after the consumption of 

 large amounts of it by partaking of winter squash (Cucurbita maxima)™ 9 

 over a prolonged period. 310 The highest concentration of lutein reported 

 by Zechmeister and Tuzson 296 in human fat was in the case of a woman 

 suffering from jaundice. 



Although lutein has not been reported in the fat of cattle, it is a con- 

 stant component of milk and butter, 311 in which the concentration varies 

 with the amount of green fodder. As might be expected, lutein has also 

 been reported in the serum of cattle. 303 



The occurrence of lutein in fowl is quite general. It has been reported 

 in chicken fat, 308 as well as in egg yolk. 302 Brockmann and Volker 312 

 observed the presence of this pigment in the feathers of the wild Madeira 



302 A. E. Gillam and I. M. Heilbron, Bioehem. J., 29, 1064-1067 (1935). 



303 A. E. Gillam and M. S. El Ridi, Bioehem. J., 29, 2465-2468 (1935). 



304 H. J. Deuel, Jr., E. R. Meserve, C. H. Johnston, A. PolgaY, and L. Zechmeister, 

 Arch. Bioehem., 7, 447-450 (1945). 



305 S. M. Greenberg, A. Chatterjee, C. E. Calbert, H. J. Deuel, Jr., and L. Zechmeister, 

 Arch. Bioehem., 25, 61-65 (1950). 



306 S. M. Patel, J. W. Mehl, and H. J. Deuel, Jr., Arch. Bioehem., 30, 103-109 (1951). 



307 J. Ganguly and H. J. Deuel, Jr., Unpublished experiments, 1952. 



308 L. Zechmeister and P. Tuzson, Z. physiol. Chem., 225, 189-195 (1934). 



309 H. Suginome and K. Ueno, Bull. Chem. Soc, Japan, 6, 221-228 fl931). 



310 M. Ansai, Japanese J. Med. Sci., V. Pathology, 1, 175-190 (1931). 



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

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



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



