236 



A. I. RIXGEK AND EMIL J. BAUMAXN 



They are usually prepared by extraction with water or alcohol, and 

 are mostly colorless, levorotatory, crystalline substances, with a bitter 

 . tasto. 



Most glucosides may be hydrolyzed by enzymes contained in the same 

 tissue, but in other cells of the same plant from which the glucoside is 

 obtained. These enzymes have the generic name of glucosidases. The 

 best known glucosidase is emulsin of almonds. It hydrolyzes only P-glu- 

 cosidcs, i. e., derivatives of p-glucose. Maltase hydrolyzes a-glueosides. 

 These specific reactions have proven very useful in the. elucidation of the 

 structure of many glucosides and polysaccharides. Myrosin, obtained 

 from black mustard seeds, is another enzyme of wide application. It 

 acts upon many glucosides, all of which contain sulphur, such as glucotro- 

 paolin, sinalbin and sinigrin. 



While d-glucose is found as a constituent of glucosides more often 

 than all other sugars, many other sugars may be found in glucoside com- 

 bination. Galactose is a constituent of a number of plant glucosides (solan- 

 in, digitonin, etc.) and of a group of substances found in nerve tissue, 

 called galactosides or cerebrosides. d-Ribose also forms important gluco- 

 sides, among which are the four nucleotides, which make up plant nucleic 

 acids. Glucosides of d-arabinose and 1-arabinose, 1-xylose and a number 

 of methyl pentoses are also known. 



TABLE V 

 SOME OF THE NATURAL GLUCOSIDES* 



Arranored after R. F. Armstrong, The Simple Carbohydrates and Glucosides, 

 Longmans, Green & Co., N. Y., 1912. 



