Oleuropein is a secoiridoid glycoside and a methyl ester of 3,4-dihydro-2H-pyran-5-carboxylic acid, substituted at positions 2, 3, and 4 with hydroxy, ethylidene, and carboxymethyl groups, respectively. The anomeric hydroxy group at position 2 is converted into a beta-D-glucoside, and the carboxylic acid of the carboxymethyl group is converted to a 3,4-dihydroxyphenethyl ester (2S,3E,4S stereoisomer). It is the most important phenolic compound in olive cultivars, acting as a plant metabolite, radical scavenger, anti-inflammatory agent, antineoplastic agent, antihypertensive agent, NF-kappaB inhibitor, apoptosis inducer, antioxidant, and nutraceutical. It is also a member of catechols, diesters, and pyrans.
