4 Purine alkaloids The purines are consisting of

4. Purine alkaloids • The purines are consisting of a six-membered pyrimidine ring fused to a five-membered imidazole ring. • three well-known examples are : • Caffeine (1, 3, 7 -trimethylxanthine), • Theophylline (1, 3 -dimethylxanthine) • Theobromine (3, 7 -dimethylxanthine).

• Biological sources: • Coffea arabica • Cola nitida Theobroma Cocoa seeds • Tea leaves (camillia sinensis)

• 1. Caffeine: • 1, 3, 7 -trimethyl xanthine occur in coffee, tea, cacao and kola usually prepared from tea or recovered from coffee roasters. CNS stimulant activity: Enhances alertness, Facilitates thought formation, Decreases the sensation of fatigue. Cardiovascular activity: Positive inotropic action, tacchycardia, slight peripheral dilation, mild diuretic action

• In combinations with antipyretics and analgesics, cold and flu medication. To increases the intestinal absorption of some of these drugs; or to counteract drowsiness. • • Side effects of caffeine Sinus tacchycardia Epigastric pain Nausea Vomiting Nervousness Insomnia tremors

Theophylline or 1, 3, -dimethyl xanthine. Pharmacological Action of Theophylline: Bronchial smooth muscle relaxant Stimulates respiratory center in the brain stem by increasing sensitivity to CO 2. CNS stimulating Slightly inotropic. Diuretic activity is stronger than that of caffeine.

Uses: Theophylline utilized principally as smooth muscle relaxants for : The symptomatic relief or prevention of bronchial asthma. Treatment bronchospasm associated with chronic bronchitis , Cough & reversible bronchospasm (chronic obstructive pulmonary disease)

• 3. Theobromine • 3, 7 -dimethyl xanthine obtained from dried ripe seed of theobroma cacao ( strerculiaceae ). Uses • Cocoa has nutritive, stimulant and diuretic properties. • Theobromine is used as a diuretic. • It has less action on the CNS than caffeine. • Oil of theobroma is used in pharmacy chiefly as a suppository base.