The olive tree is an evergreen native to the Mediterranean region and naturalized in many warm or tropical climates throughout the world. Growing to heights of 25 feet or more, the tree has a gnarled trunk with hard, yellow wood covered by greenish-gray bark. The leaves have a leathery texture and are elliptical, oblong, or spear-shaped. The top side of the leaf is dark green, while the underside is covered with silvery scales. The round, oblong fruit and the oil pressed from it are used as food. Extracts from the leaves are used for health promoting purposes.
The primary active component in olive leaves is a bitter compound called oleuropein, which the body converts into various active constituents including elenolic acid, alglycone, and calcium elenolate. Olive leaves also contain a variety of other flavonoids and phenolic compounds that may exert biological activity.
Olive leaf extract has no known toxicity, and doses of 1,600 mg per day (divided into four 400 mg doses) have been administered with no significant side effects.