108 II. DIGESTION AND ABSORPTION OF FATS 



choleic acid lattice structure, and report that the results confirm those of 

 the earlier investigations. 



(g) Factors Involved in the Formation of Choleic Acid. Desoxycholic and 

 apocholic acids are the only bile acids which share in the formation of the 

 choleic acids. On the other hand, cholic, lithocholic, and cholanic acids, 

 which are completely ineffective, have residual valences scattered in various 

 directions from the main longitudinal axis of the molecule, which lies be- 

 tween the hydroxyl group on C 3 and the carboxyl group on C 2 4. In desoxy- 

 cholic and apocholic acids, the hydroxyl on C 12 would appear to direct the 

 residual affinities to the opposite front of the molecule. Sobotka 398 sug- 

 gests that this side of the desoxycholic acid molecule presents an "ali- 

 phatic" aspect along the chain of carbons 8,4,6, 7, 8, 14, 15, 16, 17, 20, 22, 

 28, 24- A double bond inhibits this chain in dihydroxycholenic acid; in 

 the case of chenodesoxycholic and hyodesoxycholic acids, an analogous 

 affinity does not occur on the other side of the molecule, since it is inter- 

 rupted by methyl groups. 



Moreover, the conjugated desoxycholic acids, also, are known to lose 

 their ability to form choleic acids. 550 Desoxycholic acid loses its power to 

 form choleic acid when the hydroxyl groups have been formylated, or when 

 the acid has been esterified. 550 The acholic component also acquires differ- 

 ent properties from that exhibited by the free compound. Benzaldehyde, 

 for example, is no longer subject to auto-oxidation when present as benz- 

 aldehydecholeic acid. 399 



(h) Types of Coordination Compounds of Bile Acids Other Than Choleic 

 Acids. Although cholic acid cannot form choleic acid derivatives, it can 

 combine with various alcohols such as methyl and allyl, with glycol and 

 with ethyl mercaptan. 509 - 551 It likewise forms unstable compounds with 

 nitrobenzene, ra-toluidine, aniline, benzaldehyde, and triolein. 552 Bile 

 acids form coordination compounds with each other. Thus, chenodesoxy- 

 cholic acid and 3-hydroxy- 1 2-ketocholanic acid, both of which occur in 

 human bile, form a coordination compound in a molecular ratio of 1 : l. 417 



(i) Physiological Importance of Choleic Acid Formation. The hypothesis 

 that the formation of choleic acid complexes is involved in the absorption 

 of fats is most appealing. One is naturally led to the supposition that a 

 connection must obtain between the beneficial action of bile salts on lipid 

 absorption and the highly specific property of the reaction which involves 



560 F. Cortese and L. Bauman, J. Biol. Chew., 118, 771) -785 (1936). 

 551 F. Mylius, Ber., 20, 683-688; 1968-1989 (1887). 



562 S. Minovici and M. Vanghelovici, Bui. Soc. Chim. Romania, IB, 5-13 (1930); 

 Chem. Abst., 25, 521 (1931). 



