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