caffeine

Caffeine is a bitter, white crystalline xanthine alkaloid that is a stimulant drug. It is found in the leaves and seeds of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants. It is most commonly consumed by humans in infusions extracted from the seed of the coffee plant and the leaves of the tea bush, as well as from various foods and drinks containing products derived from the kola nut. Other sources include yerba mate, guarana berries, guayusa, and the yaupon holly.