420 V. CHEMISTRY OF PHOSPHATIDES AND CEREBROSIDES 



and Klenk* do not feel that these experiments offer absolute proof of this 

 hypothesis. No lecithin has been found which will not absorb iodine. ^^^ 



In the case of plant phosphatides, some instances are known in which both 

 component fatty acids are unsaturated. This would appear to be the case 

 with soybean lecithin, in which the principal unsaturated acids are linoleic, 

 linolenic, and oleic. Although palmitic and stearic acids are also present, 

 the higher proportion of unsaturated acids would seem to indicate that 

 some diunsaturated lecithins must necessarily be present. ^*^~^^^ On the 

 basis of the results of Daubney and Smedley-MacLean,^*^ it is calculated 

 that the lecithin of yeast is composed of a mixture of 75% palmito-oleo- 

 lecithin and 25% dioleolecithin. Phosphatidic acid with two unsaturated 

 acids has also been reported in cabbage. ^^^-^^^ 



b. Choline. The essential component in the lecithin molecule is the 

 quaternary ammonium base choline. This compound is likewise present 

 as one of the nitrogenous bases of sphingomyelin. It may be considered 

 to be hydroxy ethyltrimethylammonium hydroxide. It is also closely 

 related to betaine, which exerts the same qualitative physiologic effects 

 as does choline, although the quantitative relations may differ. Neurine, 

 with which choline was originally confused, is now known to differ from the 

 latter because of the vinyl side chain which replaces the hydroxy-ethyl 

 group. Muscarine, on the other hand, has an aldehyde group in place of the 

 alcohol on the ethyl side chain of choline. 



/CH3 /CH3 



HOCHeCHgN-CHj 0=CCH2N-CH3 



I^CHj '-O-'^CH, 

 OH 



Choline Betaine 



CHj=CH N-CHj HCCHjN-CHj 



I'^CH, I CH, 



OH OH ' 



Neurine Muscarine 



Choline has been referred to as sinkaline, amanitine, fagin, bilineurine, 

 as well as neurine. The term choline first appeared in the literature in 1862, 

 although Strecker, who named it, had reported its isolation from hog bile 

 13 years earlier. ^^^ Von Babo and Hirschbrunn^"*^ had also isolated the 



138 J. Cruikshank, J. Path. Bad., IS, 428-431 (1!)13 -1914). 



139 P. A. Levene aud I. P. Rolf, /. Biol. Chem., 62, 759-7t)tJ (1925). 

 i^» P. A. Levene and I. P. Rolf, J. Biol. Chem., 65, 545-549 (1925). 

 1*1 P. A. Levene and I. P. Rolf, /. Biol. Chem.. 68, 285-293 (1926). 



1*2 C. G. Daubney and L Smedley-MacLean, Biochem. J., 21, 373-385 (1927). 



1" A. C. Chibnall and PL J. Channon, Biochem. J., 21, 233-246 (1927). 



1*^ H. J. Channon and A. C. Chibnall, Biochem. J., 21, 1112-1120 (1927). 



'« A. Strecker, Ann., 70, 149-197 (1849). 



"» L. von Babo and M. Hirschbrunn, Ann., 84, 10-32 (1852). 



