40 THE SIMPLER NATURAL BASES 



trimethylamine. Some are so unstable that they cannot be formed by 

 the ordinary process of methylation. Thus aspartic acid, when treated 

 with methyl iodide and alkali, breaks up into trimethylamine and 

 fumaric acid. The same applies to tyrosine and it is noteworthy that 

 the betaines of tyrosine and of phenylalanine have never been found 

 in nature, whereas the corresponding unsaturated acids (p-cumaric and 

 cinnamic acids) are often met with in plants. The betaine of tryptophane 

 is somewhat more stable, and ergothioneine requires heating with 

 concentrated alkali to decompose it into trimethylamine and the un- 

 saturated acid. 



The free betaines when dried above 1 00 have a composition 

 corresponding to a cyclic anhydride (the second of the above formulae). 

 Salts are formed by direct addition of an acid, when the ring is broken 

 down. Most betaines crystallise with one molecule of water and in 

 this condition their constitution is probably illustrated by the for- 

 mula : 



/OH 

 (CH 3 ) 3 : N/ 



\CH 2 .COOH. 



The main physiological interest of betaines is derived from the question 

 whether they may re-enter the metabolism of plants or whether they 

 are merely waste products ; this question is further discussed in the 

 next section. Pharmacologically the a-betaines are inert, but y-butyro- 

 betaine is toxic to higher animals. 



Betaine, Trimethylglycine, (CH ) 3 : N/ 



X CH 



While searching for alkaloids in Solanacece^ Husemann and Marme 

 [1863, 1864] isolated a base from Lycium barbarum, which was 

 found to have the composition C 5 H n O 2 N and was named by them 

 lycine. Three years later Scheibler [1866] obtained from the sap 

 of the sugar beet (Beta vulgaris) and from beet molasses a " soluble 

 alkaloid" which he described in detail later [1869] and called 

 betaine. Soon afterwards Scheibler [1870] and Liebreich [1870] 

 showed the identity of betaine with oxyneurine, a base prepared by 

 Liebreich [1869, 2] by the oxidation of " bilineurine " ( = choline) and 

 also synthetically by the action of trimethylamine on mono-chloracetic 

 acid. Griess [1875] prepared betaine according to his general method, 

 by methylating glycine and Husemann [1875] proved the identity 

 of lycine with betaine ; the second (and later) name for this base has, 

 however, passed into general use. 



