PHYSIOLOGY 243 



Similar methods * have been applied to the elucidation of 

 the constitution of other glucosides, and as a result many of 

 these have subsequently been synthesized. 



The synthesis of the glucosides of a number of alcohols 

 besides methyl and ethyl alcohols, was investigated by 

 Bourquelot f who by means of the enzyme emulsin produced 

 glucosides, galactosides, and mannosides of propyl- and iso- 

 propyl-alcohols, glycol, glycerol, and cinnamyl alcohol ; for 

 this purpose the sugar was dissolved in the corresponding 

 alcohol in the presence of a little water or acetone ; all these 

 were jS-glucosides ; with the use of maltase from yeast he was 

 also able to prepare a number of a-glucosides. 



It has been shown by Armstrong that enzymes can exert 

 their synthetic action without actually being in solution, 

 acting merely as colloids in virtue of their surface. Bour- 

 quelot, moreover, drew attention to the fact that in the 

 presence of enzymes, insoluble alcohols could be converted 

 into soluble glucosides by combination with glucose ; from 

 this he concluded that the plant has in the formation of 

 glucosides a very efficient mechanism for rendering insoluble 

 substances soluble. 



In some cases the natural glucosides have been chemically 

 synthesized ; thus salicin has been obtained by the reduction 

 of the corresponding aldehyde glucoside, helicin — ■ 



CeH„06 . O . CgH^CHO + 2H = CoHnOs . O . CgH^CH^OH 



the helicin itself having been synthesized from glucose and 

 salicylic aldehyde. 



PHYSIOLOGICAL SIGNIFICANCE OF GLUCOSIDES. 



In attempting to assign the part played by these sub- 

 stances in the economy of the plant, it must be remembered 

 that glucosides of natural occurrence are very numerous, 

 and, in some cases, of a diverse nature ; it is, therefore, 

 possible that the significance of the presence of one glu- 

 coside may be quite different to that of another, but even in 

 the case of glucosides of the same nature there is much 



* Macbeth and Pryde : " J. Chem. Soc," 1922, 121, 1660. 

 t Bourquelot : " Bull. Soc. Chim.," 1913. [iv], 13. i-xxviii. 



16* 



