300 IV. DIGESTION OF LIPIDS OTHER THAN FATS 



The relative stability of /3-carotene in the intestine has likewise been 

 shown by in vitro tests. Thus Goodwin and Gregory 264 found that caro- 

 tene was not destroyed when incubated with rabbit intestinal contents 

 at 37°C; in addition, Seshan and Sen 347 reported that no carotene was 

 lost when it was incubated with cattle feces. 



Gossypol has likewise been shown to be an effective antioxidant in pro- 

 tecting carotene both in vitro and in vivo. 3iS Mattill 327 had previously 

 shown that gossypol is an effective antioxidant in protecting lard in vitro. 

 Moreover, Hove and Hove 349 reported that gossypol is able to protect 

 carotene from destruction in vitro from preformed fat peroxides. In a 

 later study, Hove 348 observed that gossypol and dianilinogossypol, when 

 fed to rats at daily doses of 1 mg., were only slightly less effective than a- 

 tocopherol in preserving carotene when diets containing lard or methyl 

 linoleate were fed. Cottonseed oil meal, which contains gossypol, was 

 shown to be equal to wheat germ in stabilizing a carotene solution in 

 ethyl oleate in vitro, and much superior in this respect to several other 

 common feeds. 



(3) The Digestibility of Carotenoids 



Most of the studies on carotenoids have been carried out with too small 

 amounts to serve as a basis for reports on digestibility by the usual balance 

 study methods. However, Johnson and Baumann 350 measured the re- 

 covery, from the feces of rats, of several carotenoids fed in cottonseed oil 

 in amounts of 2 to 78 7 daily. It was found that cryptoxanthin had the 

 highest digestibility (64%), followed by /3-carotene (60%) and a-carotene 

 (46%). The percentage excretion did not vary with the dose, nor was it 

 influenced when lutein was given concomitantly. Fraps and Meinke 351 

 had previously reported digestibility coefficients in rats of 57 and 64, 

 respectively, for /3-carotene and a-carotene dissolved in oil, while "neo-/3- 

 carotene" had practically the same digestibility as /3-carotene. 



a. Factors Affecting the Digestibility of Carotenes. The extent of di- 

 gestibility of carotene, as well as its absorption, is influenced by a number 

 of extraneous factors. 



(a) The Amount of Carotene Administered. In the case of rats, Fraps 

 and Meinke 351 reported that the digestibility of a-carotene ranged from 



347 P. A. Seshan and K. C. Sen, J. Agr. Sci., 32, 194-201 (1942). 



348 E. L. Hove, /. Biol. Che?n., 156, 633-642 (1944). 



349 E. L. Hove and Z. E. Hove, J. Biol. Chem., 156, 611-621 (1944). 



350 R. M. Johnson and C. A. Baumann, Arch. Biochem., 19, 493-501 (1948). 

 361 G. S. Fraps and W. W. Meinke, Arch. Biochem., 6, 323-327 (1945). 



