Oleuropein is a phenylethanoid, a type of phenolic compound found in olive leaf from the olive tree together with other closely related compounds such as 10-hydroxyoleuropein, ligstroside, and 10-hydroxyligstroside. All these compounds are tyrosol esters of elenolic acid that are further hydroxylated and glycosylated. It is one of the main natural phenols found in argan oil. It is also found in the leaves of privet. Oleuropein and its metabolite hydroxytyrosol have powerful antioxidant activity both in vivo and in vitro and give extra-virgin olive oil its bitter, pungent taste. Oleuropein preparations have been claimed for several pharmacological effects among them strengthening of the immune system. A study in rats suggests oleuropein enhances thermogenesis by increasing the thermogenin content in brown adipose tissue and the secretion of noradrenaline and adrenaline.
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