Olive leaf is the leaf of the olive tree (Olea europaea). Although olive oil is well known for its flavor and health benefits, the leaf has been used medicinally in various times and places. Olive leaf and olive leaf extracts (OLE), are now marketed as anti-aging, immunostimulator, antioxidant, anti-inflammatory and antibiotic agents. Though there is some laboratory evidence for these effects in biological standardization experiments (i.e., bioassays), clinical evidence in humans is inconclusive.
Clinical evidence has been conflicting regarding any blood pressure lowering effect of carefully extracted olive leaf extracts. Bioassays support its antibacterial, antifungal, and anti-inflammatory effects at a laboratory level. A liquid extract made directly from fresh olive leaves gained international attention when it was shown to have an antioxidant capacity almost double green tea extract and 400% higher than vitamin C.
The silvery green leaves are oblong, measuring 4–10 centimetres (1.6–3.9 in) long and 1–3 centimetres (0.39–1.2 in) wide.
The primary active compounds in unprocessed olive leaf are believed to be the antioxidants oleuropein and hydroxytyrosol, as well as several other polyphenols and flavonoids, including oleocanthal. Elenolic acid is a component of olive oil and olive leaf extract. It can be considered as a marker for maturation of olives. Oleuropein, together with other closely related compounds such as 10-hydroxyoleuropein, ligstroside and 10-hydroxyligstroside, are tyrosol esters of elenolic acid.
Soaps and cosmetics
Olive leaf extracts are sometimes used in skin creams and other cosmetics for application to the skin or other body surfaces. Olive leaf extract has been shown to provide antioxidant and antibacterial effects that can prolong the shelf life of cosmetic preparations. 
- Kilham, Chris, Healing Power of Olive Leaf, January 23, 2013, FoxNews.com
- Perrinjaquet-Moccetti et al. Food Supplementation with an Olive (Olea europaea L.) Leaf Extract Reduces Blood Pressure in Borderline Hypertensive Monozygotic Twins, 2008.
- Somova et al. Antihypertensive, antiatherosclerotic and antioxidant activity of triterpenoids isolated from Olea europaea, subspecies africana leaves, 2003.
- Khayyal et al. Blood pressure lowering effect of an olive leaf extract (Olea europaea) in L-NAME induced hypertension in rats, 2002.
- Zarzuelo et al. Vasodilator effect of olive leaf, 1991.
- Natural Antioxidants, Antibacterials From Olive Leaf Extracts Used In Cosmetics, Pharmaceutical, And Food Industries Fuad Al-rimawi, Prof., Imad Odeh, Abdallah Bisher, Hiba Yateem, and Mohammad Taraweh Qatar Foundation Annual Research Conference Proceedings 2014, HBPP0116. http://www.qscience.com/doi/abs/10.5339/qfarc.2014.HBPP0116