Methylxanthines are chemical compounds which are derivatives of xanthine with one or more methyl groups, including:
One methyl group: 1-Methylxanthine 3-Methylxanthine 7-Methylxanthine
Two methyl groups: Theophylline (1,3-dimethylxanthine) Paraxanthine (1,7-dimethylxanthine) Theobromine (3,7-dimethylxanthine)
Three methyl groups: Caffeine (1,3,7-trimethylxanthine)
General references