On the decomposition of caffeine in the liver. 1

The earlier workers on the metabolism of caffeine and theobromine maintained that these substances may undergo partial or complete transformation in the body with the loss of one or more of the methyl groups. Investigations carried out recently seemed to indicate that this was due to specific enzymes. Schittenhelm, Brugsch and Pincussohn 2 claimed to have found an enzyme in the lungs of the horse capable of splitting off the methyl groups of caffeine. Kotake 3 came to similar conclusions as a result of studies on the decomposition of caffeine in beef livers. He added varying amounts of caffeine to aqueous extracts of the liver which he allowed to digest under antiseptic precautions at body temperature in the thermostat for four days. Liver extracts without caffeine, similarly treated, were used as controls. At the end of each period the purin bodies were precipitated and total nitrogen determined. He found in every case much larger amounts of total nitrogen in the extract containing caffeine than in the control, from which he concluded that the increase of purin substances was due to the reduction of caffeine to non-methyllated purins.

The work of Fuijitani 4 has shown that caffeine stimulates peptic digestion in vitro. The possibility of a stimulating action of caffeine on intra-cellular enzymes is therefore not to be excluded, and might explain the results of Kotake. Moreover, in Kotake's experiments no separation of the alkaloid was attempted.