MISCELLANEOUS NITROGEN AND SULFUR COMPOUNDS 287 



These two reactions are catalyzed by two separate enzymes, /3-glycosidase and oxynitri- 

 lase. The cyanide poisoning of livestock from eating such leaves as wild cherry is a 

 practical problem of some importance, but hydrocyanic acid as such does not exist in 

 plants. It is evolved according to the reaction outlined above when the plants are injured. 

 Table 3 lists the structures of some cyanogenic glycosides along with the carbonyl com- 

 pounds which are formed from them by the two-stage hydrolysis process. 



In addition to the cyanogenic glycosides of the structure shown above, it has been 

 noted in the previous section of this chapter that nitriles sometimes arise from hydrolysis 

 of typical mustard oil glucosides. Thus, small amounts of nitriles may be present in 

 some impure mustard oils. For example, enzymatic hydrolysis of glucotropaeolin may 

 produce benzyl cyanide as well as benzyl iscthiocyanate: 



a 



// 



NOSO3 



CHoCN 



CH2C 



S-GLUCOSE 



When a nitrile is formed by such a reaction, the sulfur atom appears as elemental suLfur- 

 the only example of the occurrence of this free element in higher plants. Presumably as 

 the result of analogous reactions allyl cyanide occurs along with allyl iso-thiocyanate in 

 black mustard oil and the nitrile corresponding to sulforaphene in radish oil. These ni- 

 triles are stable, volatile compounds and do not release hydrogen cyanide. To some ex- 

 tent they may be artifacts formed from unhydrolyzed glucoside during steam distillation, 

 but there is also evidence that at least in some cases they are true natural products. 

 Careful study of this obscure reaction is needed. 



A few other miscellaneous nitriles have been found in higher plants. Consumption 

 of seeds of the sweet pea (Lathyriis uduratits) by animals causes a disease known as 

 odoratism which is characterized by changes in bone and connective tissue structure. 

 The causative agent is y-glutamyl-jS-aminopropionitrile (33): 



NH9 



HOOCCHCH2CH2CNCH2CH2CN 



Another chronic human disease known as lathyrism has been rather common in parts of 

 India and Spain. Although it is caused by eating seeds of Lathyrus sativiis or contaminat- 

 ing seeds of Vicia spp. , the causative agent is not y-glutamyl-/3-aminopropionitrile; and 

 the chief symptom is paralysis caused by irreversible nerve damage. The poisonous 

 constituent in this case is probably /3-cyano-L-alanine, which might reasonably be related 

 biosynthetically to i3-aminopropionitrile (34). 



Isolation of the cyanogenic glycosides follows the general lines described for other 

 glycosides based on their solubility in water and lower alcohols and lack of solubility in 

 most fat solvents. They also show some solubility in ethyl acetate, and this property may 



