268 NITROGEN BASES 



NH CO N(CH3)— CO 



II II 



CO C— N(CH3) CO C— N(CH3) 



/'" I 1 ^'^^ 



NfCHs) — C— N N(CH3)— C— N 



3 : 7 Dimethyl Xanthine or 1:3:7 Trimethyl Xanthine 



Theobromine or Caffeine 



Xanthine is widely distributed among plants, notably in 

 sprouting seedlings, and occurs also in tea leaves and in the 

 juice of the beetroot. 



Theobromine occurs chiefly in the fruit of Theobroma Cacao 

 (l"5-2"4 percent), and a small quantity also occurs in kola nut 

 and in tea leaves, but not in coffee ; it acts as a powerful 

 diuretic and has a stimulating effect on the central nervous 

 system, but is less powerful in this respect than caffeine. 



Caffeine occurs to the extent of about 1-2 per cent in kola 

 nuts, -i-'S per cent in cocoa beans, from 2-5 per cent in tea 

 leaves, from 0"8-i'7 per cent in coffee beans, and from 2"5-3 

 per cent in the fruit of PauUinia cupana ; the latter substance 

 ground up into a paste is consumed in South America under 

 the name of guarana. The so-called Mate or Paraguay tea, 

 the dried leaves of Ilex paraguensis^ contains about o-2-i"6 

 per cent of caffeine. 



Caffeine is a powerful cerebral stimulant, but also acts 

 somewhat on the heart ; it is furthermore a powerful diuretic. 



Three further purine bases deserve mention, namely, 

 Adenine, Hypoxanthine and Guanine, the formulae of which 

 are as follows : — 



N=CNH„ NH— CO NH— CO 



II 11 II 



CH C— NH CH C— NH NH2C C— NH 



^r-'T-T \rT-f \pH 



II II ^ II II ^ II II /- 



N— C N N C N N C N 



6 Aminopurine or 6 Oxypurine or 2 Amino 6 oxypurine or 



Adenine Hypoxanthine Guanine 



All three substances have been obtained by the hydrolysis 

 of nucleo-proteins from plants (see p. 316) and of nucleic acids 

 from yeast* and from Triticum sativum.^ 



*Schittenhelm and Schroter : " Zeit. physiol. Chem.," 1904, 41, 290. 

 + Osborne and Harris: /</., 1902, 36, ^5 ; Osborne: " Amer. Journ. Pharm.," 

 1903, 9, 69. 



