Paullinia cupana

Guaraná ( from the Portuguese guaraná [ɡʷaɾɐˈna]; Paullinia cupana, syns. P. crysan, P. sorbilis) is a climbing plant in the family Sapindaceae, native to the Amazon basin and especially common in Brazil. Guaraná has large leaves and clusters of flowers, and is best known for the seeds from its beans, which are about the size of a coffee bean. Guaraná is common in soft drinks in Brazil, and is a major source of caffeine for many South Americans. Products containing guaraná can be effective stimulants: the seeds can be up to about 6% caffeine. For comparison, green coffee beans are about 1–3% caffeine. As an additive, it has gained notoriety for being used in energy drinks. As with other plants producing caffeine, the high concentration of caffeine is a defensive toxin that repels insects from the berry and seeds. The color of the fruit ranges from brown to red and it contains black seeds that are partly covered by white arils. The color contrast when the fruit is split open has been co......read more on Wikipedia.