PRUSSIC ACID IN PLANTS 45 



then diminishes to zero. A number of the grasses have been 

 found not to contain any cyanogenetic compounds, notably 

 Cynodon Dactylon, Paspalum distichum, and sugar-cane tops 

 grown in Australia. Samples of young oats, wheat, and barley, 

 grown in Essex, have also been examined at the Imperial 

 Institute and found not to yield any prussic acid. 



Phaseolunatin. — This glucoside was isolated by Dunstan 

 and Henry l from the seeds of uncultivated plants of Phaseolus 

 lunatus grown in Mauritius, where the plant is used as a green 

 manure. It is widely cultivated in tropical and subtropical 

 countries, and yields beans which may vary in colour from 

 pale pink with purple spots (Rangoon beans) to pale cream 

 or white (Lima beans). The seeds from cultivated plants are 

 lighter in colour and less shrivelled than those produced by the 

 wild plant, and yield mere traces of prussic acid or none at all, 

 whereas the wild seed may yield as much as 0'i3 per cent, by 

 weight of the acid. 2 



Phaseolunatin is decomposed by hot dilute acids or by an 

 emulsin-like enzyme, which also occurs in the seeds, in accord- 

 ance with the following equation : 



C 10 H 17 O 6 N + H 2 = C 6 H„0 6 + HCN + (CH 3 ) 2 CO 



Phaseolunatin. Dextro-glucose. Prussic acid. Acetone. 



Phaseolunatin is therefore a glucose ether of acetonecyanhydrin. 



It is of interest to recall that in 1888 van Romburgh, 3 who 

 has been associated with Treub at Buitenzorg in the study of 

 cyanogenesis, recorded that in many plants in which cyano- 

 genesis occurs acetone is produced simultaneously with prussic 

 acid. It is probable that phaseolunatin or a similar acetone 

 glucoside is present in these plants. Among the species men- 

 tioned by van Romburgh are Ma, idiot utdissima (cassava), 

 M. Glaziovii (Ceara rubber plant), Hevea brasdiensis (Para 

 rubber plant), and Hevea Spruceana. More recently Jouck 4 has 

 shown that the glucoside isolated by Jorissen and Hairs 5 from 

 embryonic flax-plants when decomposed by acids yields acetone 

 and prussic acid. Van Itallie 6 observed that the same products 

 are yielded by the leaves of Thalictrum aqudegifoUum, and 

 suggested that phaseolunatin may be present in this plant. 



Gynocardin. — This glucoside was isolated by Power and 



1 Proc. Roy. Soc. 1903, 72, 285. 4 Jouck, loc. cit. 



2 Ibid. 5 Bull. Acad. roy. Belg. 1891 [iii.], 21, 529. 



3 Ann.jard. bot. Buit. 1899, 16, I. 6 Journ. pharm. chim. 1905, 22, 337. 



