

PHYSOSTIGMA 



325 



tigmine (eserine), which occurs in the embryo to the extent of 0.1 

 to .25 per cent. It crystallizes in rhombohedra (Fig. 147), which 

 are colored red with solutions of the alkalies and yellow with sul- 

 phuric or nitric acid. With the latter reagent the solution changes 

 to olive-green. The aqueous solutions of physostigmine are alkaline 

 and easily decomposed, with the separation of a reddish-colored sub- 

 stance, rubreserine. The salicylate and sulphate of physostigmine 

 are official, the solutions of the former being more stable. Physo- 

 stigma also contains eseridine (isophysostigmine), an alkaloid resem- 

 bling physostigmine in its physiological action; a liquid alkaloid, 



FIG. 147! Physostigmine salicylate: orthorhombic crystals from a solution in 



chloroform. 



calabarine, which is physiologically antagonistic to physostigmine, 

 and a crystalline alkaloid, eseramine, which is inactive. 



In addition a new alkaloid, physovenine, has been isolated by 

 Power (Jour. Chem. Soc., 1912, p. 978; 1913, p. 351 and p. 1988). 

 Also the following constituents: stigmasterol; sitosterol; several 

 phytosterol glucosides; a mixture of fatty acids; sugar; and resinous 

 material. 



Allied Plants. The seeds of P. cylindrospermum have been 

 substituted for Calabar bean; they are nearly cylindrical and are 

 said also to contain physostigmine. 



