102 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



GLYCURONIC ACID. 



Glycuronic acid originates as a product of the inter- 

 mediary metabolism of the carbohydrate nucleus in the 

 protein molecule. Ordinarily it is present in the urine in 

 small amounts combined with phenol, indoxyl, and skatoxyl 

 as conjugate glycuronates; but under certain conditions, 

 either as the result of an abnormal increase in the quantity 

 of these bodies just mentioned, or the ingestion of aromatic 

 substances, such as the camphors, chloral, and naphthol, 

 etc., the conjugate glycuronates appear in such quantities 

 as to give to the urine a left-handed polarization and a 

 decided reducing power on Fehling's solution. (Some glycu- 

 ronates do not reduce.) Glycuronic acid is dextrogyrate,, 

 does not ferment, and gives positive results with the orcinol 

 and phloroglucinol tests (see the pentoses). As glycuronic 

 acid itself is never present in the urine, and since the gly- 

 curonates are said to respond negatively to the orcinol test, 

 this test has been used as a means of differentiating between 

 the pentoses and the glycuronates. This is only true, how- 

 ever, of the glycuronates which do not split off the glycuronic 

 acid component during the performance of the orcinol test 

 (boiling on the water-bath with HC1). Glycuronic acid 

 forms with parabromphenylhydrazin an osazone which 

 melts at from 200-216 C. and which, if dissolved in pyridin 

 and alcohol, shows a left-handed rotation of 7 25' or 369 

 (a) D . 



A Isevogyrate urine which, upon treatment with Fehling's 

 solution, gives a yellowish precipitate and partial reduction 

 of the copper may be more than suspected of containing 

 conjugate glycuronates. 



Examine a sample of urine in the same way as under 

 pentoses. 



