36 THE SIMPLER NATURAL BASES 



azolyl-ethylamine (described in Chapter I, p. 22), but in addition a 

 small quantity of iminazolyl-propionic acid was obtained. 



Carnosine (Ignotine), C 9 H 14 O 3 N 4 . 



This substance is described in this chapter as it is a derivative of 

 y8-alanine. Carnosine is, after creatine, the most abundant base in 

 meat extract. It was discovered by Gulewitsch and Amiradz'ibi 

 [1900, 1,2]; Krim berg [1906, I] obtained 0*13 per cent, from fresh 

 ox meat. Ignotine, subsequently isolated by Kutscher [1905] 

 from meat extract and regarded by him as an isomeride, was shown 

 by Gulewitsch [1906], by direct comparison, to be identical with 

 carnosine, and the identity has been admitted by Kutscher after pro- 

 longed controversy. Carnosine has also been obtained from horse 

 meat, to the extent of 1-82 grm. per kilo. (Smorodinzew [1913]) and 

 from fish, crabs, oysters and wild rabbits. 



On heating with baryta to 140, carnosine is hydro lysed to histi- 

 dine and /3-alanine in equimolecular proportions (Gulewitsch [1907, 

 191 1 ]) according to the equation : 



C 9 H 14 O 3 N 4 + H a O = C 6 H 9 O 2 N 3 + C 3 H 7 O 2 N. 



It is, therefore, similar to a dipeptide and must be either histidyl-/3- 

 alanine or /3-alanyl-histidine ; it gives the red coloration with sodium 

 p-diazobenzene sulphonate, characteristic of histidine, and yields on boil- 

 ing with cupric carbonate a copper salt similar to that of /3-alanine. 

 Perhaps, therefore, histidyl-yS-alanine is the more likely constitution : 



CH = C CH 2 . CH . CO . NH . CH a . CH 2 . COOH 



II 'I 



N NH NH 2 



Urocanic Acid, Iminazolyl-acrylic Acid, 

 CH = C CH = CH . COOH 



N NH 



v 



CH 



This acid contains two hydrogen atoms less than iminazolyl-pro- 

 pionic acid described above and may be considered to be derived from 

 histidine by loss of ammonia, without reduction. It was discovered 

 by Jarfe" [1874, 1875] in the urine of a dog; after a few days 

 the dog ran away, and, to Jaffe's great disappointment, it was never 

 recaptured. The substance, was not observed again until Siegfried 



