Caffeine

Caffeine is a crystalline xanthine alkaloid and a stimulant drug. It is found in seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants or as enhancing the reward memory of pollinators. It is most commonly consumed by humans in infusions extracted from the seed of the coffee plant and the leaves of the tea bush. Some other sources are guarana, guayusa and yerba maté.