198 NUCLEIC ACIDS AND THE NITROGENOUS BASES 



it is therefore, a methylamine and also a dihydroxybenzene derivative. 

 The structure of adrenaline may be compared with that of tyrosine: 



COH 



/\ 



HC CH 



HC CH 



\/ : 



c 



CH 2 



CH(NH 2 )COOH 

 Tyrosine. 



from which it will be evident that adrenaline and tyrosine contain the 

 same skeleton of carbon atoms. 



The immense physiological importance of the suprarenal gland was 

 first demonstrated by Addison, in 1849, when he showed that the 

 disease now named after him, was connected with degenerative changes 

 of the suprarenal bodies. A few years later it was also discovered 

 that the suprarenal glands contain a " chromogenic substance" which 

 yields a vivid green color with ferric chloride and a red color with 

 iodine. Strangely enough, however, the remarkable effect of suprarenal 

 extracts upon blood-pressure was not discovered until 1894, and the 

 positive identification of the pressor-substances with the " chromogenic 

 substance" was not established until some years later. 



Pure adrenaline crystallizes in colorless spherules; it is sparingly 

 soluble in water and almost insoluble in most organic solvents, it will 

 however, dissolve in glacial acetic acid, ethyl oxalate or benzaldehyde. 



Adrenaline may be prepared from fresh suprarenal glands by extract- 

 ing the minced tissue with water, coagulating the proteins by heat or 

 trichloracetic acid, concentrating the extract and adding ammonia 

 which causes the adrenaline to separate out. 



The readily oxidizable catechol (orthodihydrobenzol) nucleus in 

 adrenaline is responsible for a variety of color reactions which it yields. 

 The following are among the most characteristic: 



Ferric Chloride Reaction. In neutral or faintly acid solutions adrena- 

 line yields with ferric chloride a vivid grass-green color, which changes 

 to violet, reddish violet and red on rendering the solution alkaline. 

 This will detect about one part of adrenaline in thirty thousand, but 

 the addition of Sulphanilic Acid, while changing the color to reddish 

 brown, also renders the test much^more sensitive. 



Iodine Reaction. With iodine or iodic acid adrenaline yields a red 

 color. The excess of iodine may be removed by shaking up the mixture 

 with ether. 



Mercuric Chloride. With mercuric chloride, in the presence of 

 Calcium Salts, which act as catalyzers, solutions of adrenaline yield a 

 red color. 



