264 GLUCOSIDES 



1. Aqueous extracts readily form a froth when shaken up. 



2. Concentrated sulphuric acid gives with all saponins, 

 either in the cold or on warming, a violet or red colour. 



3. Concentrated sulphuric acid containing a little ferric 

 chloride gives with many saponins a blue or bluish-green 

 colour or fluorescence. 



4. The haemolytic action described below may be tried. 

 Although the above reactions are best carried out in the 



test tube, numbers 2 and 3 may be made use of in micro- 

 chemical work. 



Physiological Action. 



The saponins are characterized by their strongly marked 

 toxic properties. Fishes, particularly, are very sensitive to 

 saponins, being killed by a solution of i part in 100,000 

 parts of water, a fact which is made use of by fishermen in 

 the East, as the fish killed by these means are not unfit for 

 human consumption. 



Saponins have a powerful solvent action on blood cor- 

 puscles, a property which is known as haemolysis. This 

 property may be connected with their tendency to combine 

 with cholesterol,* which substance they abstract from the 

 blood corpuscles thereby effecting haemolysis. 



The action may be illustrated by adding a small quantity 

 of a solution of a saponin f in 0-9 per cent sodium chloride to 

 I c.c. of a solution made by dissolving i c.c. of defibrinated 

 blood in 100 c.c. of 0-9 per cent sodium chloride ; after a 

 short time the blood corpuscles will have dissolved leaving 

 a clear solution. 



The haemolytic action may be destroyed by shaking up 

 some of the saponin solution with an ethereal solution of 

 cholesterol and then warming for some hours at 36° C. ; this 

 treatment causes the saponin to combine with cholesterol to 

 produce an inactive compound which has no haemolytic action. 



* They also combine with phj^tosterol. 



+ The saponins of Guajacum officinale and Bulnesia Sarmienti have 

 hardly any haemolytic action, and hence are only slightly toxic. 



