ORIGIN IN THE PLANT 273 



Pictet is further of opinion that among the commonest 

 changes within the plant are the methylation of hydroxyl or 

 amino groups by formaldehyde, according to the equations 



ROH + CH 2 = ROCH 3 + O 

 and RNH + CH 2 O = RNCH 3 + O 



the resulting methylated compounds being then able to 

 undergo intramolecular transformation, by which the methyl 

 group can enter the ring, and so produce, for example, a 

 pyridine ring from methyl pyrrole, a reaction which he has 

 been able to effect in the laboratory by heat. 



CH 



CH CH CH CH / \ 



(i ({ M r^u r*u 



-> - CH CH 



CH CH CH CH 



\ / \ / CH CH 



NH NCH 3 \ ^ 



N 

 Pyrrole Pyridine 



Similar changes would also explain the formation of quin- 

 oline and isoquinoline, and it thus becomes possible to account 

 for the origin of the pyridine and quinoline rings which occur 

 in alkaloids, by assuming them to have been produced as 

 above from pyrrole or indole rings, which are the normal con- 

 stituents of protein (e.g. proline, histidine, tryptophane, etc.). 



In support of these views, Pictet states that he was able 

 to isolate by steam distillation from various leaves,* etc., 

 treated with sodium carbonate, a number of simple bases which 

 he calls proto-alkaloids ; these include pyrrolidine and methyl 

 pyrroline 



CH 2 CH 2 CH CH 



CHg CH,j CH 2 CH 2 



NH NCH 3 



Pyrrolidine Methyl pyrroline 



whose origin from the protein molecule is readily intelligible, 

 in view of the fact that a similar ring occurs in proline, the 

 cleavage product of a number of proteins. It is assumed that 

 these proto-alkaloids are subsequently methylated, rearranged 

 and condensed as described above to form the more complex 

 alkaloids. 



It has been suggested by Pictet that the secretion of 



* The leaves used were those of tobacco, carrot, parsley, and coco. 



18 



