280 LECTURE XIII. 



The transformation of uric acid into allantoine by oxidation is very 

 important: NH CH NH 



oo ( i ;co. 



X NH CO NH/ 



Allantoine 



There are a large number of compounds important to the biologist which 

 are very closely related to uric acid. We have mentioned that the nucleic 

 acids, when decomposed, produced purine bases; in fact, the following: 

 xanthine, hypo-xanthine, adenine, and guanine. Their structural formulae 

 are as follows : 



HN CO HN CO HN CO 



COC NH COC NH. HC C NH v 



HN C NH HN C N N C N 



Uric acid = Xanthine = Hypoxanthine 



2, 6, 8-trioxypurine 2, 6-dioxypurine 6-oxypurine 



NH CO N = C NH 2 



I I II 



NHa.C C NH HC C NH 



N C NT N C N 



Guanine = Adenine = 



2-amino-6-oxypurine 6-aminopurine 



In this connection we will add that substances closely related to the 

 purines have also been separated from the vegetable kingdom. These are 

 caffeine, theobromine, and theophylline. The first two are found in table 

 accessories, caffeine being present in coffee and tea, while theobromine is 

 a constituent of cocoa. The relation of these three compounds to one 

 another is indicated by their formulae: 



CH 3 .N CO HN CO 



I I /CH 3 | | CHs 



CO C N^ CO C N^ 



I ii ^r<"pr I ii x 



/s^ n yfrPTT 



CH 3 . N C N f CH 3 . N C N f l 



Caffeine = Theobromine = 



1, 3, 7-trimethyl-2, 6-dioxypurine 3, 7-dimethyl-2, 6-dioxypurine 



CH 3 . N CO 



C NH 



I II VH 



CH 3 .N C N^ C 

 Theophylline = 

 1, 3-dimethyl-2, 6-dioxypurine 



