GLUCOSIDES 87 



A study of the hydrolysis reactions of amydalin shows that 

 there are three different linkages in the molecule which may be 

 broken by the simple interpolation of a single molecule of water 

 and a fourth which may be split by a different type of hydrolysis, 

 namely, the C=N linkage. These are indicated by the numbers 

 below the corresponding portion of the formula above. Most 

 hydrolyzing agents break the molecule first at (1), yielding one 

 molecule of glucose and one of mandelo nitrile glucoside (see page 

 77). The next step usually breaks the latter at the point indi- 

 cated by (2), yielding glucose and benzaldehyde cyanhydrin, or 

 mandelo nitrile. The latter in turn breaks down at (3) into ben- 

 zaldehyde and HCN. But when amygdalin is boiled with con- 

 centrated hydrochloric acid, the first change is the splitting off 

 at (4) of the nitrogen in the form of ammonia and the consequent 

 conversion of the CN group into a COOH group, producing amyg- 

 dalinic acid. On further hydrolysis, this breaks up in the same 

 order as before. Similarly, it is possible to convert mandelo 

 nitrile into mandelic acid by splitting off the nitrogen to form a 

 COOH group, instead of splitting off the HCN group leaving 

 benzaldehyde. 



The mandelo nitrile glucoside contains an asymmetric carbon 

 atom which is wholly outside its glucose group, thus CeHioOs O 

 CeHo-CH-CN. Hence, it may exist in dextro, levo, and racemic 

 forms. In the amygdalin molecule, it exists in the dextro form, 

 which has been named " prunasin." The levo form, known as 

 " sambunigrin," has been obtained by hydrolysis of a compound 

 isomeric with amygdalin, w r hose composition has not been def- 

 initely worked out; while the racemic form, known as " pru- 

 laurasin," has been prepared from isoamygdalin, by the action of 

 alkalies. Hence, all the possible compounds indicated by the 

 presence of the asymmetric carbon have been found and identified. 



The crude enzyme preparation which is obtained from almond 

 seeds, known as " emulsin," contains two enzymes, amygdalase, 

 which breaks the amygdalin molecule at linkage (1), and prunase, 

 which breaks it at (2). The action of amygdalase must always 

 precede that of prunase. In other words, it is never possible to 

 break off a disaccharide sugar from the molecule, either by the 

 action of prunase alone, or by means of any other hydrolytic agent. 



Dhurrin, Ci-iHiTOyN, is another glucoside of fairly general 

 occurrence in plants, which yields HCN as one of the products of 



