ON THE CHEMICAL ASPECTS OF CYANOGENESIS IN PLANTS. 145 



jfVic Chemical Aspeds of Gi/anogenesiH in Plants. Bij Professor 

 Wykdham Dunstan, M.A., LL.D., F.lt.S., and T.A. Henry, 

 D.Sc. 



[Ordered by the General Committee to be printed in cxtenso.'] 



The production of prussic acid by a plant was recorded for the first time 

 by a Berlin pharmacist named Bolnn, ' who obtained it by distilling water, 

 which had been in contact with crushed bitter almonds. Since then the 

 formation of this highly poisonous substance, under conditions similar to 

 those noted by Bohm, has been observed by many investigators working 

 on widely difterent plants, and at the present time considerably more 

 than a hundred plants, belonging to twenty-two different natural orders, 

 have been observed to yield prussic acid. During recent years consider- 

 able progress has been made in the investigation of this phenomenon 

 (which may conveniently be referred to as ' cyanogenesis '), especially in 

 elucidating the nature of the immediate precursors of the acid in plants 

 and the processes by which it is liberated. 



'Natuke of 'Cyanogenesis.' 



In the great majority of cases in which the isolation of prussic acid 

 from a plant has been recorded no attempt has been made to ascertain 

 whether it occurs free or is produced by the decomposition of some more 

 complex primai-y substances occurring in the plant. Indeed, it has been 

 assumed that the acid occurs free in many of the plants in which it has 

 been found. 



In all plants in which ' cyanogenesis ' has been thoroughly investi- 

 gated it has been shown that although some free prussic acid may exist,^ 

 there is always present in addition a cyanogenetic glucoside, which is 

 readily decomposed by an associated enzyme, yielding the acid. 



Until quite recently only one of these cyanogenetic glucosides — viz., 

 amygdalin — was well known, but during the last few years, since our dis- 

 covery of lotusin in 1901, and of dhurrin in 1902, several additions have 

 been made to this class of substances. 



Amyfjdalin. 



This, the best-known member of the class, was isolated from bitter 

 almonds by Robiquet and Boutron-Charlard in 1830,^' and was first 

 thoroughly investigated by Liebig and Wohler.'' It has the formula 

 CjoH^jO, iN, and on hydrolysis by the enzyme emulsin, which occars botli 

 in sweet and bitter almonds, or by hot dilute mineral acids, yields a 

 molecule each of prussic acid and benzaldehyde and two molecules of 

 dextrose. 



C,„H„,0„N -t- 2H,0 = HCN + C'„H,CHO + 2C,H,,0, 

 Amygdalin. Prussic acid. Benzalde- Dextrose. 



hyde. 



' ^'eucs Allfjemehics Jour7ial der Chcmie, 1S03. 



■ Ann. Chim. Phys., 1830 (ii.), 44, 352. » Ann. Chcm. P/iarm., 1837, 22,:il. 



1906. L 



