ALKALOIDS 



171 



(for example, Nymphaeaceae) do not contain isoquinoline alkaloids 

 but contain other types of alkaloids. Certain families (for example, 

 Ranunculaceae) may contain isoquinoline derivatives and in addition 

 other types of alkaloids. Most of the families hsted contain several 

 types of isoquinolines. The Magnoliaceae contain, in addition, proto- 

 alkaloids, the simplest group of alkaloids, which are also derived from 

 aromatic amino acid metabolism. 



General conclusions from the over-all distribution of iso- 

 quinoline alkaloids are that their wide occurrence among the Ranales 

 indicate phylogenetic interrelationship. Outside this group (for ex- 

 ample, in the Amaryllidaceae) they occur infrequently, and then the 

 specific mode of secondary ring closure differs, indicative of parallel 

 evolution. These Amaryllidaceae alkaloids, the lycorine types, have a 

 different type of linkage between the benzyl and heterocyclic 

 N-containing ring of the basic benzylisoquinoline. In the Leguminosae 

 the Erythrina alkaloids, regarded as possible isoquinoline derivatives, 

 may also be interpreted as indole derivatives. An exception is the 

 family Rutaceae wherein almost a full array of isoquinoline alkaloids 

 of the same types as occur in the Ranales are to be found. 



Gibbs (1954) has noted the striking parallelisms to be found 

 in the alkaloids of the sub-families Papaveroideae and Fumarioideae 

 of the Papaveraceae. (However, see Chapter 6 for the distribution of 

 6-acetylornithine in these sub-families.) These sub-families are con- 

 sidered to be separate families by some systematists. It is more than 

 a question of the common presence of isoquinolines which relates these 

 sub-families. The extent of alkaloid parallelism is striking. Proto- 

 berberines, aporphines, phthalideisoquinolines, and protopines occur 

 widely throughout both sub-families. Phthalideisoquinolines are rare 

 outside the Papaveraceae while protopine is found elsewhere only in 

 Nandina (Berberidaceae). Gibbs states: 



We must not let the finding of protopine in a plant outside the 

 Papaveraceae blind us to the very strong evidence from the work of 

 Manske and others that the Papaveroideae, Hypocoideae and Fumar- 

 ioideae are indeed very closely allied chemically. This work is one of 

 the best examples of the worth of comparative chemistry applied to 

 taxonomy. 



Actually, demonstration of alkaloid similarities in the sub- 

 families of Papaveraceae does not necessarily bear upon the question 

 of whether the two taxonomic groups should be considered as sub- 

 families or as families. The significant point is that they have been 

 closely linked. The taxonomic position, as long as such a link is 

 emphasized, is a matter of descretion. 



