The structure of xanthine.

Xanthines are a group of alkaloids that are commonly used for their effects as mild stimulants and as bronchodilators, notably in treating the symptoms of asthma. They include caffeine, theophylline, theobromine (found mainly in chocolate).

The core compound, xanthine, is a product on the pathway of purine degradation and is converted to uric acid by the action of xanthine oxidase.

Xanthines are purine derivatives and found very rarely in constituents of nucleic acids.