ALKALOIDS 



161 



In contrast, many of the indole alkaloids such as strychnine 

 (see below) are quite complex. Sometimes it is impossible to deter- 

 mine whether certain of these alkaloids are reduced indole or reduced 

 isoquinoline derivatives (for example, some Erythrina alkaloids such 

 as erysopin). Therefore, the systematic distribution may provide clues 

 to the interpretation of the alkaloid's biosynthetic affinities. Rep- 

 resentative indole alkaloids are the following: 



H3CO 



CH, 





CH3 CH3 



harmine 



physostigmine 



H3COOC 



yohimbine 



HO 



rauwolfme 



H3COOC 



alstonine 



PYRIDINE ALKALOIDS 



This group includes alkaloids in which the pyridine nucleus 

 itself is preserved as well as those with a reduced pyridine, or piperi- 

 dine, nucleus. The alkaloids may be quite simple (pyridine itself is 

 found in Haplopappus hartwegii) or moderately complex. Simple 

 pyridine derivatives such as coniin are found in numerous families 

 among gymnosperms, monocots, and dicots. Since pyridine is a part 

 of the fundamental coenzyme complex involved in oxidative phos- 

 phorylation, repeated evolution of simple pyridine derivatives is not 

 surprising. Although the pyridine alkaloids are widely distributed 



