ABSORPTION AND DIGESTIBILITY OF HIGHER ALIPHATIC ALCOHOLS 255 



solution, as proposed by Gardner and Fox. 29 Dam 30 indicated the possi- 

 bility that, when the hydrolysis of cholesterol esters is carried out with 

 alkali, cholesterol may be so altered that it can no longer be determined by 

 the usual methods of analysis. The separation of cholesterol esters from 

 neutral fat in blood by the use of a differential hydrolysis technic has not 

 proved satisfactory. 



Cholesterol esterase has a wide distribution in the tissues, including 

 the intestinal wall (see page 21); this enzyme is specific in effecting the 

 hydrolysis of cholesterol esters, while other lipases are inactive. Reichel 

 and Reinmuth 31 demonstrated that castor bean lipase is devoid of any 

 action on cholesterol stearate, although it has a potent action on triglyc- 

 erides. Kelsey 32 based a procedure for the separate determination of 

 neutral fat and cholesterol esters with castor bean lipase upon this varia- 

 tion in enzyme composition. 



The fate of cholesterol esters in the gastrointestinal tract appears to be 

 identical with that of the free alcohol. The discussion of absorption, 

 transformations in the gastrointestinal tract, and digestibility of both the 

 ester and the free alcohol forms of cholesterol is included in a later section 

 (see page 259). For a treatment of the absorption and digestibility of the 

 carotenoid esters or vitamin A esters, the reader is referred to later sec- 

 tions in this chapter. 



4. The Absorption and Digestibility of Higher Aliphatic Alcohols 



The higher aliphatic alcohols are much less widely distributed in nature 

 than are the sterols. Some of them apparently are natural products, the 

 metabolism of which is closely connected with that of the corresponding 

 fatty acids. The greatest amount of information is available as to the 

 behavior of cetyl, stearyl, and oleyl alcohols. 



(1) Cetyl Alcohol 



Cetyl alcohol, CH 3 (CH 2 ) 14 CH 2 OH, was first shown by Gardner 33 to be a 

 component of feces. Schoenheimer and Hilgetag 34 were later able to 

 isolate it from the feces of man, dogs, and cats. It was likewise isolated 

 from the human intestinal walls, from meconium (sterile feces of the new- 



29 J. A. Gardner and F. W. Fox, Biochem. J., 18, 1058-1069 (1924). 



30 H. Dam, Biochem. Z., 194, 177-187 (1928). 



31 L. Reichel and W. Reinmuth, Z. physiol. Chem., 244, 78-80 (1936). 



32 F. E. Kelsey, J. Biol. Chem., 180, 187-193 (1939). 



33 J. A. Gardner, Biochem. J., 15, 244-273 (1921). 



34 R. Schoenheimer and G. Hilgetag, J. Biol. Chem., 105, 73-77 (1934). 



