Purine alkaloids occur in various parts of the world and are used in stimulant beverages as it consists of caffeine, a CNS stimulant principle. Various plants like tea, coffee, cola, cocoa, guavana and mate contains the derivatives of xanthine, they are called purine alkaloids.
Purine alkaloids mainly includes caffeine, theobromine and theophylline.
These alkaloids contain purine base, which is a fusion of an imidazole and pyrimidine rings. Purine base is derived into xanthine and this to caffeine (1,3,7 trimethyl xanthine), theobromine (3,7 dimethyl xanthine), theophylline (1,3 dimethyl xanthine). Xanthine does not occur free in nature.
Although they are known as alkaloids, they do not respond to common alkaloidal reagents. They give a positive murexide colour reaction. They are sublimatary in nature.
All these 3 alkaloids have stimulant and diuretic properties. Caffeine has mainly stimulating effect and theobromine has diuretic effects. Theophylline has both the above activities and mainly smooth muscle relaxant properties.
