MISCELLANEOUS NITROGEN AND SULFUR COMPOUNDS 



295 



NITRO COMPOUNDS 



Only three nitro compounds have been isolated from higher plants, but their very 

 rarity contributes to their interest. Naturally occurring nitro compounds are reviewed 

 by Pailer (63). /3-nitropropionic acid (hiptagenic acid) occurs in a variety of unrelated 

 plants such as the violet (Viola odorata), creeping indigo (Indigofera endecaphylla), and 

 the fungus Aspergillus flavus. The toxic compounds karakin and hiptagin from Corynocar- 

 piis laevigata and Hiptage madablata respectively are glucose triesters of this acid. It is 

 of some economic importance since it is toxic to animals who may eat plants containing 

 it. 



Aristolochic acid found in Aristolochia clematitis is a nitrophenanthrene. 

 oil oi Aniba canellila contains 80?o l-nitro-2-phenylethane (64). 



The bark 



NOo 

 I ^ 

 CH2CH2COOH 



i3-nitropropionic acid 



CH2CH2NO2 



l-nitro-2-phenylethane 



OOH 



aristolochic acid 



Nothing is known regarding the physiological function or biosynthesis of these com- 

 pounds in higher plants. It has been shown (65) that in fungi /3-nitropropionic acid is syn- 

 thesized from aspartic acid. The alkaloids of Aristolochia are based on the aporphine 

 nucleus, which has almost the identical carbon-nitrogen structure as aristolochic acid: 



aporphine nucleus 



