commonly known as the Dragon's Eyes, Eyeball tree, is a tropical tree species that produces edible fruit. It is one of the better-known tropical members of the soapberry family Sapindaceae
, to which the lychee
also belong. The fruit of the longan is similar to that of the lychee, but less aromatic in taste. It is native to tropical Asia and China.
The longan, is so named because it resembles an eyeball when its fruit is shelled (the black seed shows through the translucent flesh like a pupil/iris). The seed is small, round and hard, and of an enamel-like, lacquered black. The fully ripened, freshly harvested fruit has a bark-like shell, thin, and firm, making the fruit easy to peel by squeezing the pulp out as if one were "cracking" a sunflower seed. When the shell has more moisture content and is more tender, the fruit becomes less convenient to shell. The tenderness of the shell varies due to either premature harvest, variety, weather conditions, or transport/storage conditions.
Dragon's Eyes is a large tree, up to 15 m tall, with a dense, symmetrical crown and rough bark. Alternate, compound leaves are up to 30 cm in length, with 6-9 pairs of leaflets. Flowers are staminate, pistillate and hermaphroditic, small, whitish, produced in panicles in leaf axils or at ends of branches. Fruits are round, 1-2.5 cm in diameter, with a rough, light brown peel. One peeling, what emerges is a translucent, whitish ball of pulp with a smooth black seed inside. This is probably what inspired the name Dragon's Eyes and Eyeball tree. Dragon's Eyes is found in Indomalaysia and throughout the Western Ghats.
The flesh of the fruit is administered as a stomachic, febrifuge and vermifuge, and is regarded as an antidote for poison. A decoction of the dried flesh is taken as a tonic and treatment for insomnia and neurasthenic neurosis.
In both North and South Vietnam, the 'eye' of the longan seed is pressed against a snakebite in the belief that it will absorb the venom. Leaves and flowers are sold in Chinese herb markets but are not a part of ancient traditional medicine. The leaves contain quercetin and quercitrin. The seeds are administered to counteract heavy sweating and the pulverized kernel, which contains saponin, tannin and fat, serves as a styptic.