318 GLYCURONIC ACID 



group to a carboxyl, thus giving a phenol-glycuronic acid 

 the constitution: 



CH.O.c 6 H 5 

 H.C.OH 



According to Emil Fischer it is very improbable that free 

 glycuronic acid is first formed, as it cannot well be imagined 

 why the CH 2 (OH) group should be oxidized while the much 

 more labile aldehyde group is preserved. However, this 

 objection is of less force if one supposes that the aldehyde 

 group is protected by first fixing an alcohol or a phenol 

 group, after which the terminal CH 2 OH group undergoes 

 oxidation into COOH. 



Conjugation Conditions. Very many foreign substances 

 when introduced into the body are finally excreted with the 

 urine in the form of conjugate glycuronic acids. However, 

 the alcohols and phenols alone are capable of direct conjuga- 

 tion. Aldehydes and acetones must first be reduced to alco- 

 hols (as chloral, CC1 3 .COH, to CC1 3 .CH 2 .OH; acetone, CH 3 . 

 CO.CH 3 , to CH 3 .CH(OH).CH 3 ). Hydrocarbons of the aro- 

 matic and hydroaromatic series are hydroxylized (as ben- 

 zol into phenol) ; and heterocyclic compounds undergo 

 analogous hydroxylation (as indol into indoxyl). These 

 relations have been thoroughly proved by numerous studies 

 by Jaffe, Neuberg, Fromm, Hildebrandt, Neubauer, Hama- 

 lainen, and others. 49 



49 Cf. Literature: C. Neuberg, Handb. d. Pathol. d. Stoffw., 2d ed., 2, 225, 

 228, 1907, and Ergebn. d. Physiol., 3, 385-390, 1904; C. Neuberg and W. Nei- 

 mann, Zeitschr. f. physiol. Chem., 44, 114 1905; E. Salkowski and C. Neuberg, 

 Biochem. Zeitschr., 2, 307, 1906; R. Hildebrandt (Halle), Hofmeister's Beitr., 

 7, 438, 1906; Hamalainen (Helsingfors), Skandin. Arch. f. Physiol., 27, 141, 

 1912; J. Schiiller (M. Cremer's Lab., Cologne), Zeitschr. f. Biol., 56, 274, 1911 ; 

 J. Saneyoshi (C. Neuberg's Lab.), Biochem. Zeitschr., 36, 22, 1911. 



