GLUCOSIDES 77 



Most of the common glucosides are derived from d-glucose. 

 Some are known, however, which are derivatives of galactose or 

 rhamnose; while in some cases the exact nature of the sugar which 

 is present has not vet been determined 



HYDROLYSIS OF THE NATURAL GLUCOSIDES 



All natural glucosides are hydrolyzed into a sugar and another 

 organic residue by boiling with mineral acids; although they vary 

 widely in the ease with which this hydrolysis is brought about. 



In most cases, the glucoside is easily hydrolyzed by an enzyme 

 which occurs in the same plant tissue, but in different cells than 

 those which contain the glucoside. Injury to the tissues, germina- 

 tion processes, and perhaps other physiological activities of the 

 cells, result in bringing the enzyme in contact with the glucoside 

 and the hydrolysis of the latter takes place. A large number of 

 such enzymes have been found in plants, many of which hydrolyze 

 only a single glucoside. Howe.ver, two enzymes, namely, the 

 emulsin of almond kernels, and myrosin of black mustard seeds, 

 each hydrolyze a considerable number of glucosides. In general, 

 emulsin will aid in the hydrolysis of any glucoside which is a 

 derivative of 0-glucose, and myrosin will help to split up any sulfur- 

 containing glucoside. Glucosides which are derivatives of rham- 

 nose require a special enzyme, known as rhamnase, for their 

 hydrolysis. 



The following reactions for the hydrolysis of arbutin and of 

 amygdalin are typical of this action, and will serve to illustrate 

 the general structure of these compounds: 



CH 2 OH-CHOH-CH-CHOH-CHOH-CH'O-C 6 H 4 OH + H 2 O 



Arbutin 



= C6Hi 2 O 6 -h HOCeKiOH 



Glucose Hydroquinone 



C 6 H 5 



(a) C 6 HiiO5-O.C 6 Hio04-O-CH + H 2 O 



Amygdalin 



CN 



+ C 6 Hi20 6 



Mandelo-nitrile I Glucose 



glucoside 



