Approximately 100 species of plants and herbs contain caffeine. Caffeine is less commonly found in fruits, but the kola nut contains caffeine, as do the seeds from the fruit of the Guarana plant and the cacao tree.
Guarana plants produce small fruits that have seeds with a higher concentration of caffeine than coffee beans. Some species of the coffea plant produce edible red and purple fruits called cherries. These cherries contain seeds which have caffeine. Lemon, grapefruit and orange plants contain caffeine in their leaves and flowers, but not in the fruits themselves.
Most fruits that come from flowering plants do not contain caffeine. Naturally occurring caffeine found in plants and seeds often acts as a defense mechanism to discourage herbivores from eating the plant.