Caffeine is a xanthine alkaloid compound that acts as a stimulant in humans. Caffeine is sometimes called guaranine when found in guarana,mateine when found in mate,and theine when found in tea. It is found in the leaves and beans of the coffee plant, in tea, yerba mate, guarana berries, and in small quantities in cocoa, the kola nut and the Yaupon Holly. Overall, caffeine is found in the beans, leaves, and fruit of over 60 plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding upon them. Its name is derived from the Italian caff� ("coffee") plus the alkaloid suffix -ine.