METHYLATED PURIN DERIVATIVES 



167 



CAFFEIN 



CH, NH CO 



/ /CH, 



CO C N<^ 



CH,-NH C-N/ 



PARAXANTHIN 



CH.-N CO 

 CO C-N-CH, 

 Vd-N> CO 



1-MONOMETHYL- 

 XANTHIN 



CH 8 N CO 

 CO 



THEOBROMIN 

 N CO 



/ \ /CH, 

 CO C N< 



\ >CO 



CH, N C N/ 



THEOPHYLLIN 

 CH, N CO 



CO C Nv 

 CH, N-C-N/ 



7 MONOMETHYLX AN- 

 THIN ( = HETEROXANTfflN) 



N CO 



CO 





C- 



N-CH, 



3 MONOMETHYL- 

 XANTHIN 



N CO 



CO C N x 



\ I >CO. 

 CH, N C N/ 



It is possible apparently that the demethylation, how- 

 ever, can proceed further and may in the end lead to the pro- 

 duction of uric acid and allantoin, for which reason the 

 prohibition of coffee, tea and chocolate is probably always 

 advisable in prescribing diet for a case of gout 58 ; although 

 the methylxanthins are likely to increase the purins sooner 

 than the uric acid in the urine. The methyl derivatives 

 of xanthin are entirely absent from the urine of an individual 

 who has abstained completely from coffee and tea ; but this 



is not true of epiguanin [ (NH)C X 



N CO 

 ' I /CH 3 \ 



C N<^ 1 a guamn de- 



rivative which cannot originate from any of the known 

 purins of coffee and tea. 59 It is possible that we are here 

 dealing with an example of the methylation processes in 

 the body which have been previously considered (v. supra, 

 p. 132). Demethylation of methylated xanthin deriva- 



58 A. Schittenhelm, Therap. Monatsch., 1910, 113; P. Fauval, Compt. Med., 

 142, 1428, 1906; 148, 1541, 1909. 



w M. Kriiger, Biochem. Zeitschr., 15, 361, 1909. 



