1,3,8-Trimethylallantoin: a major caffeine metabolite formed by rat liver

: The formation of 1,3,8-trimethylallantoin from caffeine is demonstrated for the first time in vitro in rat liver slices. This compound constitutes 15% of total in vitro metabolites. With this identification, all the metabolic pathways of caffeine shown in vivo (N-demethylation, oxidation to uric acids and formation of uracil and allantoin derivatives) are demonstrated in vitro.