THE SPHINGOMYELINS ' 461 



lyzed ox liver. The product had a melting point of 156-157°C. and yielded 

 only sphingosine and lignoceric acid on hydrolysis. Moreover, it was 

 showTi that the conditions prevailing throughout the saponification of 

 sphingomyelin and the subsequent isolation of the ceramide were so mild 

 as to preclude the adventitious formation of ligiiocerylsphingosine. 



This ceramide has no free carboxyl group and is inactive toward nitrous 

 acid. This is taken to indicate that a NH — CO union exists between the 

 acid and the sphingosine. 



CH3{CH2),2CH=CHC-C-CH2 OH 



H NH 

 I 



CO 

 I 

 (CHjljj 



CHj 



Lignocerylsphiugosine 



Although palmitic acid was at first thought to be present in the molecule, 

 it was later shovm to be an impurity. Lignocerylsphiugosine is the only 

 ceramide which has as yet been identified as a hydrolysis product of sphin- 

 gomyelin. In contradistinction to the sphingomyelins, the ceramides are 

 soluble in ether; they can also be crystallized from acetone. ^*^ However, 

 in the case of the cerebrosides, not only lignocerylsphingosine has been pre- 

 pared, but also cerebronyl-.V-sphingosine. 



b. Sphingosine. Sphingosine was first prepared as the sulfate from 

 the cerebroside phrenosin by Tliudichum.-''^-^ The pioneer work in estab- 

 lishing its structure was done by Lapworth^'"^ and by Levene and West.^"-^^* 

 These investigators believed that sphingosine has an empirical formula of 

 C1-H35NO2 and a structural one of CH3(CH2)iiCH:CHCHOH-CHOH- 

 CH2NH2. Klenk^^^ was unable to confirm these earlier observations, since 

 he consistently obtained myristic and palmitic acids, respectively, on oxi- 

 dation of sphingosine and of dihydrosphingosine with chromic acid. Levene 

 and West had earlier identified these acids with the C13 (tridecylic) and C15 

 (pentadecylic) acids. Klenk further showed that the analyses of many 

 sphingosine derivatives were much more in harmony with an assumed com- 

 position of C18H37NO2 than with one of C17H35NO2. It was also pointed out 

 i)y Klenk that the earlier workers had based their opinions almost exclus- 

 i\'ely upon carbon and hydrogen analyses, while a better criterion to es- 



^^ J. L. \V. ThucUc-hum, Further Researches on the Chemical Coiislilulion of the Brain 

 and of the Organoplastic Substances, Xiiitli .Viinual Report of the Local Government 

 Board, 187i)-1880. Suppl. B, No. :], lieport ol the Medical Officer for 1879, London, 

 l)p. 14:i-20l>. 



"« A. Lapworth, J. Chem. Soc, 103, 102»)-U);i4 (1913). 



"' P. A. Levene and C. J. West, ./. Biol. Chem., 16, 549-553 (1913-1914). 



"8 P. A. Levene and C. J. West, ./. Biol. Chem., IS, 481-484 (1914). 



"' E. Klenk, Unpublished observations, cited from H. Thierfelder and E. Klenk, Die 

 Chemie der Cerebroside und Phosphatide, Springer, Berlin, 1930, p. 42. 



