It is classified as a xanthine alkaloid (more specifically, a methylxanthine), others of which include theophylline and caffeine. Caffeine differs from these compounds in that it has an extra methyl group (see under Pharmacology section).<unk>  is a slightly water-soluble (330 mg/L), crystalline, bitter powder.<unk>  is white or colourless, but commercial samples can be yellowish. It has an effect similar to, but lesser than, that of caffeine in the human nervous system, making it a lesser homologue.<unk>  is an isomer of theophylline, as well as paraxanthine.<unk>  is categorized as a dimethyl xanthine.
Theobromine
Phosphene
Benzoctamine
Cromoglicic acid
Chlorotrianisene
Magnetophosphene
Adapromine
Lepromin