IX] GLUCOSIDE-SPLITTING ENZYMES 151 



Aesculin is characterized by giving in water solution a blue fluor- 

 escence which can be detected even in great dilution. The fluorescence 

 is increased in alkaline, and decreased in acid, solution. 



Expt. 149. Demonstration of the presence of aesculin in Aesculus bark. Strip oft' 

 the bark from .some young twigs oi Aesculus and boil in a little water in an evaporating 

 dish. Filter and i)our the filtrate into, exces.s of water in a large vessel. A blue 

 fluorescent .solution will be formed. 



Glucoside.s of Flavone, Flavonol and Anthocyan Pigments. 

 These substances have already been considered in Chapter vii. 



Glucoside.s of various Composition. 



Coniferin. This glucoside occurs in various members of the Coniferae 



and also in AsparcKjus. On hydrolysis with mineral acids or emulsin, it 



breaks up as: 



CH =CHCH,,OH 



A. 



C]„Ho,Os + H.,0 = C,;Hi20,, 

 Coniferin 



V 



0CH3 



OH 



Coniferyl alcohol 



Arbutin. This glucoside is found in the leaves of the Bearberry 

 {Arctostaphylos Uva-ursi), Pyrola, Vaccinium, and other Ericaceae and 

 also of the Pear (Pi/rus communis). 



On hydrolysis with acids arbutin yields hydroquinone and glucose: 

 CioHieO^ + H.,0 = CaHfiOo + CgHjoO,, 

 the same hydrolysis is brought about by the enzyme emulsin. 



It has been suggested that the darkening of leaves of the Pear 

 (Bourquelot and Fichtenholz, 11, 12, 13) either on autolysis or injury, or 

 at the fall of the leaf, is due to the hydrolysis of the arbutin by a gluco- 

 side-splitting enzyme in the leaf, and subsequent oxidation of the 

 h3i'droquinone so formed by an oxidase. 



Evpt. 150. Ex-traction of arbutin from leaves oj the Pear (Pyrus connnunis). 

 Weigh out 100 gms. of fresh leaves (without petioles). Tear the leaves into small 

 pieces and drop them as quickly as possible into about 500 c.c. of boiling 96-98 % 

 alcohol in a flask. Boil for about 20 mins., adding more alcohol if necessary. Then 

 filter off' the alcohol and pound uj) the leaf residue in a mortar and extract again with 



