oleuropein

Oleuropein is a naturally occurring secoiridoid glycoside and a major phenolic compound found in the olive tree (Olea europaea). It is most abundant in olive leaves and in unripe olives, and is responsible for much of the characteristic bitterness of raw olives.

Chemistry and metabolism: Oleuropein consists of a hydroxytyrosol moiety linked to elenolic acid by a glycosidic bond; upon hydrolysis, oleuropein yields hydroxytyrosol and elenolic acid, and oleuropein aglycone is formed when the glycosidic bond is removed.

Occurrence and biosynthesis: It is produced by the olive tree as part of its defense chemistry and is one of the most studied phenolics in the olive family. Levels vary with cultivar, maturity, and plant tissue.

Processing and sensory: In olive processing, oleuropein contributes bitterness; during fermentation or debittering, enzymatic hydrolysis reduces levels, yielding milder olives and olive oil with lower oleuropein.

Biological activities: Oleuropein and its hydrolysis products exhibit antioxidant, antimicrobial, and anti-inflammatory properties in laboratory studies, and may contribute to the health effects associated with the Mediterranean diet. Clinical evidence is limited and results are inconsistent.

Uses and significance: It is used as a chemical marker for olive oil authenticity and quality; olive leaf extracts rich in oleuropein are sold as dietary supplements. Safety: Generally regarded as safe in food contexts, but high intake can cause gastrointestinal discomfort in some individuals.