2 58 GLUCOSIDES 



of pancreas.* The complexity of this enzymic mixture is 

 shown by the fact that its activity on the substrate amygdaUn 

 can be separated into two stages : — 



(1) C,oH2,NOu + H^O = Ci^H^NOe + CeH,,Oe 



Mandelonitrile 

 glucoside 



(2) Ci^H^NOe + H3O = QH5CHO + HCN + C^H^fi^ 



The first of these reactions is effected by the enzyme 

 amygdalase, whilst the second is produced by the enzyme 

 prunase. 



The two stages of the hydrolyses may be demonstrated 

 either by carefully controlling the reaction of emulsin on 

 amygdalin and stopping the reaction at the right moment, 

 before the prunase is able to decompose the mandelonitrile 

 glucoside, or else by hydrolysis by means of acids. f 



According to Giaja $ amygdalin is broken up under the 

 action of the gastric juice of the snail, Helix pomatia, into 

 benzaldehyde, hydrocyanic acid and a disaccharide which has 

 since been identified as gentiobiose. 



This disaccharide has not as yet been isolated from amyg- 

 dalin, but the fact of its presence there is proved by Campbell 

 and Haworth § and Kuhn and Sobotka || who synthesized 

 amygdahn from gentiobiose. The constitution of gentiobiose 

 having been determined by Haworth, Helfferich and other 

 as a jS-glucosido-^-glucose, the constitution of amygdalin 

 becomes — 



QHs 



CH2OH CH 



— O J . O ^ ^ 



(CHOH)3 . CH . O . CH2CH (CHOH)3 CH . O . CH 



CN 



Some confusion originally existed as to whether amygdalin 

 contained a- or jS-glucose residues. Thus yeast extract is 

 able to split off a molecule of glucose from amygdalin, giving 

 mandelonitrile glucoside ; this action was wrongly attributed 

 to maltase, the prototype of a-glucosidases ; actually this 



* Oppenheimer : " Lehrbuch der Enzyme," Leipzig, 1927, p. 271. 



t Caldwell and Courtauld : " J. Chem. Soc," 1907, 91, 666. 



X Giaja : " Compt. rend.," 1910, 150, 793. 



§ Campbell and Haworth : " J. Chem. Soc," 1924, 125, 1337. 



II Kuhn and Sobotka: " Ber. deut. chem. Gesells.," 1924, 57» B., 1767. 



