HYDROLYSIS OF CEREBROSIDES 4S7 



of pentaacetA'lcerasinc is similar to that of the corresponding phrenosino 

 compound except that the former is less soluble in methyl alcohol. ^-^ 

 Pentaacetylcerasine melts at 54-56°C./" and has a specific rotation of 

 — 16.46°'*^^ at 20°C. in a 1:1 mixture of chloroform and methyl alcohol. 



Penlamethylcerasine originates on meth^/lation of the parent corapoimd 

 with methyl iodide and silver iodide. It is a white amorphous compound 

 melting at 73°C.'*" Benzoijlcerasine dissolves in cold methyl alcohol. 

 This reaction serves as a means of separation of cerasine from phrenosine, 

 since the corresponding cerasine derivative is insoluble in this solvent. 



The same non-specific chemical tests as those used for phrenosine, which 

 are based upon the presence of the galactose molecule, also serve equally 

 well for the detection of cerasine. 



(5) Nervone 



Nervone corresponds closely to the other cerebrosides as regards its 

 solubilities. Like cerasine, its solubility somewhat exceeds that of phreno- 

 sine. It behaves like cerasine under the polarization microscope and in the 

 selenite plate test. It melts at 180°C. but changes at a lower temperature 

 to a semiliquid state. It is levo-rotatory {[otf^ pyridine ^ —4.33°). 

 The iodine number is 62.7. 



The only known compound of nervone is the lead salt. This precipitates 

 when alcoholic lead acetate and ammonia are added to a hot alcoholic solu- 

 tion of the cerebroside.'*" 



6. Hydrolysis of the Cerebrosides 



On hydrolysis, the cerebrosides are split into sphingosine, a fatty acid, 

 and galactose or glucose. The hydrolysis of galactosidophrenosine pro- 

 ceeds as follows: 



C48H93NO9 + 2 H,0 > C24H48O3 + CsHstXO. + CeHi.Oe 



Phrenosine Cerebronic Sphingosine, Galactose, 



acjd, 46.4% 36.2% 21.7% 



The reaction can be brought about in aqueous solution, -''-•^^^•^^- and in ethyl 

 alcoholic sulfuric acid,^^--^^-"^^'* but the best results are obtained wi(li 

 methyl alcoholic sulfuric acid.^'*^-'*'*" In the latter case, one obtains the 

 methyl ester of cerebronic acid, methyl sphingosine, and methyl galacto- 

 side. For the hydrolysis, about 3 g. of the cerebroside is refluxed with 150 



*" P. A. Levene and C. J. West, J. Biol. Chem., SI, 635-647 (1917). 



"" P. A. Levene and G. M. Mever, J. Biol. Chem., 31, 627-6:34 (1917). 



*" H. Thierfelder, Z. physiol. Chem., 44, 366-:370 (1905). 



*** 0. Riesser and H. Thierfelder, Z. physiol. Chem., 77, 508-510 (1912). 



**^ J. L. W. Thudichum, Further Researches on the Chemical Constitution of the Brain. 

 Report of the Medical Officer, Privj' Council, Local Government Board, n..s., 8, 

 No, 6, London, 1876, pp. 117-150. 



