CHEMISTRY OF SAPONINS 185 



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 one 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 rendering them soluble. 



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 solvent action on 

 blood corpuscles. 



Chemistry of the Saponins. 



As already stated, the majority of saponins are neutral 

 substances, while a few have feebly acid properties. Only a 

 single saponin, namely, Solanin, has basic properties ; this 

 substance, which occurs in Solanum nigrum, S. dulcamara and 

 in the fruit of potatoes, owes its basic property to the presence 

 of a nitrogen atom (see Nitrogen Bases, p. 263), and appears 

 to form a connecting link between the saponins and the 

 alkaloids. 



The neutral saponins are precipitated from solution by 

 basic lead acetate, while acid saponins are precipitated by lead 



* They also combine with phytosterol. 



+ The saponins of Guajacum officinale and Bulnesia Sarmienti have hardly 

 any haemolytic action, and hence are only slightly toxic, 



