158 



GLUCOSIDES 



[CH. 



the glucoside, the different sugar groups are removed separately b}^ 

 different enzymes (see later, emulsin, p. 160). 



The glucosides as a whole (except flavone, flavonol and anthocyan 

 pigments) are colourless crystalline substances. When extracting them 

 from the plant, it is usually necessary to destroy the accompanying 

 enzyme by dropping the material into boiling alcohol or some other 

 reagent (see autolysis, p. 20). 



In Chapter v it has already been mentioned that c?-glucose exists in 

 two stereoisomeric forms, the a and the /3 form. 



It was also pointed out that the glucosides can be classed either as 

 a- or y8- glucosides, according to whether the a or the yS form of glucose 

 combines with the non-glucose residue. 



RO— Cr- H H— C^^OR 



H 



HO 



H 



C— CH 



I 

 C— H 







I 

 H_C— OH 



I 



CH2OH CH2OH 



a-glucoside /3-glucoside 



Maltose, for instance, is regarded as an a-glucoside of cZ-glucose. It 

 has been further shown that the enzyme maltase can only hydrolyze 

 a-glucosides, whereas other enzymes, e.g. the prunase component of 

 emulsin, only act on yS-glucosides. 



The various glucosides considered in detail in this chapter together 

 with some others are grouped under the following headings (Arm- 

 strong, 3): 



Products of hydrolysis 



Alcohols 

 Glucose 4- coniferyl alcohol 



Glucose + saligenin + benzoic acid 

 Glucose + saligenin 

 Glucose + syringenin 



Aldehydes 

 Glucose -f benzaldehyde -|- prussic 



acid 

 Glucose 4- parahydroxy benzaldehyde 



4- prussic acid 

 Glucose -H acetone + prussic acid 



Glucoside 



Coniferin 



Populin 



Salicin 



Syringin 



Amygdalin 



Dhurrin 



Linamarin 



Plant in which commonly 

 found 



(Coniferae, Beta^ Asparagus^ 



Scorzonera) . 

 {Populus) 

 (Salix, Populus) 

 {Ligustrum, Syringa^ Jasmi- 



num) 



{Prunus^ Pyrus) 

 {Sorghum) 

 {Linum^ Phaseolus) 



