Till Mi I IBOI i-M OF PROI 



Formation occurs, giving what may be regarded as an imidazole deriva- 

 tive (see page 604). Creatine is also related to one of the import 

 diamino acids, arginine, since both contain goanidine radic 



NIL 



/ 

 \H=C and to histidine and the purines see pi - »oth 



\ 



XII 



of which contain the imidazole ring. The close relationship which 

 creatine bears to urea is illustrated by the Eacl that urea is I 



when creatine is subjected to the action of boiling barium hydrate. When 

 it is oxidized by moans of potassium permanganate, urea is also fi 

 the remainder of the molecule, more or less intact, being split off 



XII-CH3 



/ 

 motlivl-amino-acetic acid (CH, ), also known osine. 



\ 



COOH 



The conversion of creatine to creatinine goes n slowly in aqueous 

 solutions, but is much accelerated by heating with acid. Heated in an 

 autoclave at a temperature of 117 C. for thirty minutes, with half nor- 

 mal hydrochloric acid, the creatine goes over almost quantitatively into 



atinine. It will be noted that the creatinine ring is partly oxidi. 

 This renders it unstable, so that creatinine in the presence of alk; ; 



- the power of reducing metallic oxides. Like glucose it can 

 alkaline solutions of copper, silver and mercuric salts: it al> 

 picric acid in weakly alkaline solution to picramic acid, which, beii 

 furnishes us with a solution the si _•■ which can be estimal 



colorimetrically. 



Quantitative Estimation. — Although the presence of creatinine in the 

 urine has been known for many years, there being from 1 to 2 g : - 

 it in the twenty-four-hour urine, little prog] 38 - in the study 



of its metabolism because of the absence of a reliable method 

 estimation. The elaboration by Folin of a colorimetric quantitati 

 method for creatinine, depending on the reduction of pici id, has 



Furnished the starting poinl for the modern work which has been d< 

 To estimate the creatine by this method, it is usual to pr< 

 lows: The creatinine content is first of all ither ! ' 



of urine being then heated with acid in the autoclave until all 

 creatine 1; m converted into creatinine. A. £ terminal 



creatinine is then made, and the dif ie between the two - 



at inc. 



