150 GLUCOSIDES AND [ch. 



Pound about 5gms. of Black Mustard seed in 'a mortar and then boil with water. 

 Some mustard oil will be formed before the myrosin is destroyed, so that boiling 

 should be continued until no pungent odour can be detected. Then filter and cool 

 the solution and divide into two parts. To one add some myrosin solution. To the 

 other an equal quantity of boiled enzyme solution. After i hour the smell of ally! 

 isothiocyanate should be detected in the unboiled tube. 



Saponins. 



These substances are very widely distributed, being found in the 

 orders: Araliaceae, Caprifoliaceae, Combretaceae, Compositae, Cucurbi- 

 taceae, Graminaceae, Guttiferae, Lecythidaceae, Leguminosae, Liliaceae, 

 Loganiaceae, Magnoliaceae, Myrtaceae, Oleaceae, Piperaceae, Pitto- 

 sporaceae, Polemoniaceae, Polygalaceae, Primulaceae, Proteaceae, 

 Ranunculaceae, Rhamnaceae, Rosaceae, Rutaceae, Saxifragaceae, 

 Thymelaeaceae and the majority of the orders of the cohort Centro- 

 spermae. On hydrolysis with dilute mineral acids the saponins yield 

 various sugars — glucose, galactose, arabinose, rhamnose — together with 

 other substances termed sapogenins. 



The saponins are mostly amorphous substances readily soluble 

 in water (except in a few cases) giving colloidal solutions. These 

 solutions froth on shaking, and with oils and fats they produce very 

 stable emulsions. By virtue of this property they have been used as 

 substitutes for soap. The Soapwort {Saponaiia) owes its name to the 

 fact that the root contains a saponin. 



COUMARIN GlUCOSIDES. 



These substances are hydroxy derivatives of coumarin, which itself 

 may be represented as: 



Aesculin is one of the best known of these glucosides. It occurs in 

 the bark of the Horse Chestnut {Aesculus B ippocastanum). On hydro- 

 lysis with dilute acids it yields glucose and aesculetin, the latter being 

 represented as: 



^o 



:CH— CO 



OH 



