Hydroxytyrosol is a phenylethanoid, a type of phenolic phytochemical with antioxidant properties in vitro. In nature, hydroxytyrosol is found in olive leaf and olive oil, in the form of its elenolic acid ester oleuropein and, especially after degradation, in its plain form. Hydroxytyrosol itself in pure form is a colorless, odorless liquid. The olives, leaves and olive pulp contain large amounts of hydroxytyrosol (compared to olive oil), most of which can be recovered to produce hydroxytyrosol extracts. However, it was found that black olives, such as common canned variety, containing iron(II) gluconate contained very little of the original hydroxytyrosol, as iron salts are catalysts for its oxidation. Hydroxytyrosol can also be produced endogenously as it is a product of dopamine oxidative metabolism known as DOPET (3,4-dihydroxyphenylethanol). Hydroxytyrosol is mentioned by the scientific committee of the European Food Safety Authority as one of several olive oil polyphenols that may contribute to protecting blood lipids against oxidation.