Microbial alkaloids plant origin

In contrast to antibiotics of microbial origin that could be classified as alkaloids from a chemical point of view in many instances, and which often interfere with the biosynthesis or maintenance of the cell wall (mu-rein) (Table IV), such an interaction has not been described for plant-derived compounds. Since this topic has not been studied in detail it remains open whether this complex is another target for alkaloids. 

Among the alkaloids in this chapter derived from tryptophan, some do not retain the original nucleus of tryptophan, such as quinine, obtained from Cinchona plants (Rubiaceae), camptothecin, originally from Camptotheca acuminata (Cornaceae), and pyrrolnitrin of microbial origin. 

The biosynthesis of these alkaloids has been little studied. The origin of the various parts of the molecule has been suggested (Fig. 37.5). In general, the biosynthesis of ansa-mycin antibiotics of microbial origin and maytansanoids from higher plants are related (Smith and Powell, 1984). 

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