Obtained from the leaves of the olive tree (Olea europaea); these contain oleuropein, which is the main active principle of the olive tree. The use of this traditional herb dates to the early 1800s, when it was used as a remedy for various ailments. This compound has been recognized for several health-boosting benefits throughout the years. In the early 1900s, oleuropein was determined to be part of the olive tree's powerful disease-resistant structure. Other European research determined this compound to have strong antioxidant capabilities as well. Biochemists have determined that the extract has multiple natural iridoids, flavonoids, and esters; and that the synergy of these working together is the reason for the wide-spectrum effect.

Olive leaf extract has been used clinically in its present form for years. Living up to its promising background, it has demonstrated considerable therapeutic action against free radicals.