488 V. CHEMISTRY OF PHOSPHATIDES AND CEREBROSIDES 



ml. of methyl alcohol containing 10% sulfuric acid (by weight) for 3 or 4 

 hours over the water bath. 



The hydrolysis of cerasine proceeds in a similar manner: 



C48H93NO8 + 2 H2O > C04H48O2 + C18H37NO2 + CeHisOe 



Cerasine Lignoceric Sphingosine, Galactose, 



acid, 45.4% 36.9% 22.2% 



The hydrolysis of cerasine proceeds most satisfactorily with methyl alcohol 

 containing 10% of sulfuric acid; however, a period of 7 or 8 hours is re- 

 quired to complete the hydrolysis. 



In the case of nervone, the hydrolysis results in the following reaction : 



C48H91NO8 + 2 H2O > C24H46O2 + C18H37NO2 + CeH.aOe 



Nervone Nervonic Sphingosine, Galactose, 



acid, 45.2% 37.0% 22.2% 



Details of the separation of the various components from the hydrolysis 

 mixture are reported b}' Thierf elder and Klenk.* 



Barium hydroxide is a poor hydrolyzing agent. When cerebrosides are 

 heated at boiling temperature with saturated barium hydroxide for several 

 hours, no decomposition of the cerebroside occurs.*-^ This resistance to 

 hydrolysis is made use of in the removal of phosphatide impurities by saponi- 

 fication. 



7. Chemistry and Properties of Hydrolysis Products of the 



Cerebrosides 



(1) Psychosine 



Thudichum^^^'"**^ first described a product of the incomplete hydrolysis of 

 phrenosine which was formed when the fatty acid was split from the cere- 

 broside molecule. This substance was called psychosine. Thudichum-^- 

 later obtained an impure preparation of this substance from cerasine as 

 well. These findings were later confirmed by Klenk,^*'' who showed that 

 psychosine could be prepared by hydrolysis of cerebrosides with barium 

 hydroxide. Psychosine can likewise be prepared from a mixture of cere- 

 brosides containing largely nervone and hydroxynervone.^^'' It would 

 therefore appear that the sugar-sphingosine complex, psychosine, is present 

 in all types of cerebrosides; in fact, the structure of the cerebrosides which 

 we now accept is, in all cases, based upon this type of structural relationship 

 of the sugar and sphingosine. In view of the new structure of sphingosine 

 established by Carter et a^.,^i"-^*^ the formula of galactopsychosine as postu- 



**^ J. L. Thudichum, Further Researches in Chemical Biology, Seventh Annual Report 

 of the Local Government Board, 1877-1878. Suppl. Abt. B, No. 2, containing Report of 

 the Medical Officer for 1877, London, pp. 281-301. 



'*■' E. Klenk, Z. physiol. Chem., 153, 74-82 (1926). 



«8 H. E. Carter, F. J. Glick, W. P. Norris, and G. E. Phillips, /. Biol. Chem., 170, 

 285-294 (1947). 



