CYANOGENETIC SUBSTANCES 1 85 



glycoside containing the carbohydrate component, primeverose 

 [6-(B-D-xylosido)-D-glucose]. 



^-0 



IfOH^ 



CH 



2 



HO 



OH 



r—f ^9t-o-ch2N=n+ch3 



macrozamin 



Macrozamin represents one of the few known occurrences of 

 linked nitrogen atoms in a natural product (see Chapter 6). Systemat- 

 ically it is interesting in that a "new" synthetic ability is associated 

 with a primitive plant. Although such a situation should not be un- 

 expected, it may appear to be paradoxical if one should suppose that 

 primitiveness necessarily implies evolutionary quiescence. It is not 

 likely that the ability of cycad species to form linked N is of recent 

 origin, however, since the compound is found in at kast three cycad 

 genera. The important theoretical point is that macrozamin could 

 represent a recently acquired synthetic ability even though the cycads 

 themselves are phylogenetically old. The other pseudo-cyanogenetic 

 compounds, hiptagin and karakin, differ from each other in the posi- 

 tion of fusion of the nitrogen-containing group (B-nitropropionic acid: 

 NO2— CH2— CH2— COOH). 



karakoside = 1:4:6 tri-(B-nitropropionyl)-D-glucopyranose 

 hiptaside = 1:5:6 tri-(B-nitropropionyl)-D-glucopyranose 



Relatively httle is known concerning the origin of cyano- 

 genetic glycosides. Butler and Butler (1960) reported that when 

 white clover was supplied with C^* labeled isoleucine and valine, 

 radioactivity appeared in the aglycone portion of lotaustralin and 

 linamarin respectively. However, radioactivity failed to appear when 

 C14 labeled glycine and vahne, labeled only in the 1-C, were supplied. 

 These results suggested that isoleucine and vahne are involved in the 

 metabolism of these cyanogenetic glycosides, and that the formation 

 of the cyanide grouping includes decarboxylation. 



The role of cyanogenetic substances is unknown. Ideas that 

 they represent protective agents, wastes, or reserve energy sources are 

 distinctive neither by virtue of originahty nor their susceptibihty to 

 direct experimentation. 



Distribution of cyanogenetic substances in the plant is rather 

 widespread although apparently the leaves are particularly rich. 

 Green fruits in some cases are richer in cyanogenetic compounds than 

 are the mature fruits (for example, in Nandina domestica). In some 

 genera (for example, Vicia) only the seeds are cyanogenetic, and in 



