166 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



NH 2 



Creatine. NH=c-N-CH 2 . COOH. 



CH 8 



Creatine, or methyl guanidirie acetic acid, is a constituent of all 

 vertebrate muscle and is most abundant in voluntary muscle. The 

 creatine content of the muscle of any particular species is remarkably con- 

 stant ; thus -5 per cent, in rabbit's, "45 per cent, in cat's, -39 per cent, 

 in man's, 37 per cent, in dog's muscle. It is not present normally in 

 human urine, but appears under certain conditions, e.g. when carbo- 

 hydrates are absent from the food, in diabetes and other diseases. It is 

 present in the urine of infants and children and in that of women after 

 menstruation, and during and after pregnancy. Creatine is normally 

 present in bird's urine. 



Preparation. 



Creatine is more readily prepared from meat or from urine than by 

 synthesis. 



(1) From meat. 



Finely minced meat is extracted several times with hot water. The 

 aqueous solution is boiled to remove coagulable proteins and filtered. The 

 filtrate is treated with lead acetate so long as a precipitate is formed and again 

 filtered. Excess of lead is removed from the solution by means of hydrogen 

 sulphide and the filtrate from lead sulphide is evaporated down to a small 

 volume. Creatine crystallises out as the solution stands. It is filtered off 

 and washed with 88 per cent, alcohol. 



(2) From urine. 



A solution containing chiefly creatinine is obtained from urine as described 

 on p. 169. Folin 1 has given the following method of preparing creatine 

 from it : 



The solution is evaporated to dryness on the water-bath and the residue 

 dissolved in 15-20 parts of boiling water. Twice as much 95 per cent, 

 alcohol is added to this boiling solution. Nearly the whole of the creatine 

 separates out in a few hours ; it is filtered off after standing in a cool place for 

 about 1 2- 1 6 hours and washed with dilute alcohol (i part water, 2 parts 

 alcohol). 



The filtrate and washings are placed in a large flask and kept in a water- 

 bath at 80-90 for a week. The creatinine is converted into creatine ; the 

 conversion of the creatinine can be controlled by removing samples and esti- 

 mating it (p. 171), but the weight of the flask and its contents must be known. 



The solution is evaporated to dryness; the residue is dissolved in boiling 

 water so as to make a 10 per cent, solution of the creatinine still present and 

 2 volumes of alcohol added as above. This procedure can be continued 

 until nearly the whole of the creatinine is converted into creatine. About 

 30 per cent, of material is lost, but a yield of creatine equal in weight to that 

 of the creatinine is obtained. 



l ]. BioL Chem., 1914, 17, 463. 



