LIPIDS PRESENT IN BRAIN AND NERVOUS TISSUE 747 



acid : aldehyde ratio of 20:1 in this fraction. On the other hand, Klenk, 

 Debuch, and Daun 237 reported that choline-containing acetal compounds 

 (lecithins) do not occur in the brain. 



The aldehyde components of the plasmalogens of the brain consist ex- 

 clusively of Cu, Cie, and Ci 8 compounds. 225 These have been identified as 

 follows 238 ' 239 : 



Saturated aldehydes: Tetradecanal (trace) 



Hexadecanal 



Octadecanal 

 Unsaturated aldehydes: Hexadecenal (trace) 



A 9 -Octadecenal 



A u -Octadecenal 



Thannhauser et al. 2i0 reported that the acetal a-phospholipids of brain do 

 not contain unsaturated aldehydes. Palmitic aldehyde was present in a 

 greater proportion than was stearyl aldehyde. 



b. Cerebrosides in the Brain. Cerebrosides were discovered by Thudi- 

 chum, 219 who coined the name because he prepared these substances from 

 the cerebrum. Although phrenosine and cerasine (kerasine) were the only 

 two types of cerebrosides originally described, two additional compounds, 

 namely nervone 241 and oxynervone, 242 have since been discovered. Klenk 

 and Faillard 243 demonstrated the presence of two new additional isomeric 

 unsaturated hydroxy acids in brain cerebrosides which had hitherto been 

 unrecognized. These acids were proved to be : 



A^-n-a-hydroxytetracosenoic acid, CH 3 (CH 2 ) 7 CH: CH(CH 2 ),2CHOHCOOH, 

 A^-n-a-hydroxytetracosenoic acid, CH 3 (CH 2 ) 5 CH : CH(CH 2 ) 14 CHOHCOOH. 



This brings to six the known varieties of cerebrosides, which vary only in 

 the composition of the C24-acid. 



In 1940, Halliday and co-workers 244 demonstrated that two general 

 classes of cerebrosides occur in animal tissues, one containing galactose as 

 the carbohydrate component — called galactolipids — and the second class 

 containing glucose and referred to as the glucolipids. Presumably each 



237 E. Klenk, H. Debuch, and H. Daun, Z. physiol. Chem., 292, 241-250 (1953). 



238 E. Klenk, Z. physiol. Chem., 282, 18-21 (1945). 



239 F. Leupold, Z. physiol. Chem., 285, 182-200 (1950). 



240 S. J. Thannhauser, N. F. Boncoddo, and G. Schmidt, J. Biol Chem., 188, 427-430 

 (1951). 



241 E. Klenk and R. Harle, Z. physiol. Chem., 189, 243-253 (1930). 



242 E. Klenk, Z. physiol. Chem., 157, 291-298 (1926). 



243 E. Klenk and H. Faillard, Z. phijsiol. Chem., 292, 268-275 (1953). 



244 N. Halliday, H. J. Deuel, Jr., L. J. Tragerman, and W. E. Ward, J. Biol. Chem., 

 132, 171-180 (1940). 



