The Individual Purines

Caffeine or Theine.

These two names are applied to a well known purine discovered in 182o in tea leaves by Ferdinand Runge. Caffeine is found only in vegetable matter, occurring to the extent of 0.8-1.7% in coffee beans, o• 1–o.8% in cocoa beans, 1-2% in Kola nuts, 2-5% in tea leaves, and 2.5-5% in guarana, the roasted fruit of Paullinia, which is eaten in South America. It is this purine, along with theobromine and theophylline, which gives the stimulating effects to drinks made from the above sources.

Caffeine has the notable effect of stimulating the central nervous system. In addition it is a cardiac tonic, and, in common with nearly all purines, has a strong diuretic action. In the body it is oxidized to uric acid and excreted as such. There is a tendency among many medical practitioners to warn patients to do without tea and coffee. In certain cases there are undoubtedly very good reasons why caffeine is harmful. For example, in the case of a person suffering with gout, everything must be done to lower purine ingestion, and thus to lessen the load on the already over burdened kidneys. Specially prepared brands of tea or coffee are available from which caffeine has been removed without any alteration of taste. In the case of tea this is done by extracting the leaves with light petroleum to remove the volatile oils which are responsible for the flavour. The caffeine is then removed by

extraction with chloroform, after which the original petroleum extract is added to the leaves and the solvent allowed to evaporate, thus restoring to the tea its original flavour. Green coffee beans are treated with live steam and ammonia gas to swell them, the caffeine is then chloroform processed, and the beans subsequently roasted.

Theobromine.

This purine is unfortunately named, for it is devoid of bromine. It was noted first by A. Woskresensky, in 1842, in an extract of cocoa beans, where it occurs to the extent of 1.5-2.4%. This bean is the seed of the plant Theobroma Cacao hence the name theobromine. As in the case of caffeine and theophylline, it occurs only in plant matter, being present in the kola nut and in tea leaves, but not in coffee beans. It is a powerful diuretic, and in the body is oxidized to and excreted as uric acid.

Theophylline.

In 1888 A. Kossel discovered very small traces of this purine in tea extract.

Paraxanthine, Heteroxanthine, 1-Methylxanthine and Epiguanine have all at one time or another been isolated from human urine. They are regarded as secondary products, arising from the action of the body on caffeine (see p. 78o).