X] GLUCOSIDES 165 



Pound about 5 gms. 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 h hour the smell of allyl 

 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, Gramineae, 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 wdth oils and fats they produce very stable 

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

 for soap. The Soapwort (Saponaria) 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: 



CH=:CH— CO 



Ao I 



V . 



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

 the bark of the Horse Chestnut (Aesculus Hippocastanum). On hydro- 

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



represented as: 



CO 



J 



