The Nature and Origin of the Poison of Lotus arabicus. 375 



Egyptian vetch is due to the prussic acid which is formed when the 

 plant is crushed with water, owing to the hydrolytic action of an 

 enzyme, lotase, on a glucoside, lotusin, which is broken up into hydro- 

 cyanic acid, dextrose, and lotoflavin, a yellow colouring matter. 



The authors have continued the investigation with the object of 

 ascertaining the properties and chemical constitution of lotoflavin and 

 of lotusin, and also of studying the properties of lotase in relation to 

 those of other hydrolytic enzymes. 



Lotusin. 



Lotusin can be separated from an alcoholic extract of the plant 

 by a tedious process giving a very small yield, about 0*025 per cent. 



Lotusin is a yellow crystalline glucoside, more soluble in alcohol 

 than in water. When heated it gradually decomposes without 

 exhibiting any fixed melting point. Combustions of specially purified 

 material gave numbers agreeing with those deduced from the formula 

 C2SH31NO16. 



In the preliminary notice the formula C22H19NO10 was provisionally 

 assigned to lotusin on the assumption that one molecule of dextrose is 

 formed by its hydrolysis. The formula given above, as the result of 

 ultimate analysis, is confirmed by the observation that two molecules 

 of dextrose are produced by acid hydrolysis, which is therefore repre- 

 sented by the equation — 



C 28 H 31 N0 16 + 2H 2 = 2C 6 H 12 6 + HON + CmHioO,. 



Lotusin. Dextrose. Prussic Lotoflavm. 



acid. 



When a solution of lotusin is warmed with dilute hydrochloric acid, 

 hydrolysis readily occurs. The liquid acquires a strong odour of 

 hydrocyanic acid and a yellow crystalline precipitate of lotoflavin is 

 thrown down, whilst the solution strongly reduces Fehling's solution. 

 Dilute sulphuric acid only very slowly effects the hydrolysis of 

 lotusin. 



When warmed with aqueous alkalis, lotusin is gradually decomposed, 

 ammonia being evolved and an acid formed to which the name lotusinic 

 acid has been given. 



C23H 3 i0 lt3 + 2H 2 = C2sH 3 20 ls + NH 3 . 



Lotusinic acid is a monobasic acid furnishing yellow crystalline 

 salts. It is readily hydrolysed by dilute acids forming lotoflavin, 

 dextrose and heptogluconic acid (dextrose-carboxylic acid) : 



Ci 5 HioO(5 + CeH^Oe + C7H14OS. 

 Lotoflavin. Dextrose. Heptogluconic 

 acid. 



2 D 



C2 8 H 3 20 1S + 2H20 = 



Lotusinic 

 acid. 



VOL. LXVIII. 



