Oleuropein related compounds

Several minor oleuropein related compounds were isolated in olive, reported in Figure 8. Compound 21, demethyl-oleuropein, is a hydrolysis product of conjugated methyl ester present in oleuropein. The presence of this compound increases during the olive ripening [6-9],... 

Soler-Rivas C, Espin JC and Wichers HJ. 2000. Oleuropein and related compounds. J Sci Food Agric 80(7) 1013-1023. 

Oleuropein and its metabolites are terpenoids present in all parts of plant and represent the chemotaxonomic markers of O. europaea. Tyrosol, hydroxy-tyrosol and related compounds represent the main characteristic phenolic fraction of O. europaea and are recognised as very powerful anti-oxidising agents. 

Oleuropein antioxidant activity was evaluated "ex vivo", in rats treated with 100 mg/kg of the compound [96]. Plasma and bile were collected and assayed for chemiluminescence reaction. The addition of a solution of antioxidant to a glowing steady-state chemiluminescent reaction temporarily interrupts the light output. The light emission is restored after a time interval that is related to the amount of anti-oxidant added [97]. Bile was collected at 30 min interval for 2 hrs plasma was collected before sacrifice. No difference of light emission was measured with plasma from controls and treated animals. Bile samples of treated animals showed a significant inhibition (90%) of the light emission compared with bile samples from control animals (60%). 

ABSTRACT This review summarises the chemistry of Olea europaea, in particular of hydrophilic components, which are seen as the key compounds responsible for several properties, identified as the organoleptic characteristics of foods derived from O. europaea and as the biological properties attributed to this plant, like ipotensive, anti-oxidising, etc. In fact, two groups of polar compounds can be identified in O. europaea terpenenoids, as oleuropein phenols, as hydroxy-phenyl ethanol derivatives and compounds related to these two categories. 

The chemistry of oleuropein and of other phenolic components of O. europaea is described, in relation also with the biological activity of these compounds. O. europaea represents, in fact, a key plant in the economy of Mediterranean region, and olives are the key component of Mediterranean diet. Olives, olive oil in particular, represent a unique food in the scenario of Mediterranean region and they certainly have contributed to the evolution of civilisation of this part of the world. 

In the olive, there are two main compounds, besides that reported in the literature. The first one is oleuropein, the first secoiridoid isolated in 1960 by Panizzi in Roma, as mentioned above. The second one is the comoside that is a hemiquinone glucoside, structurally and biogenetically related to hydroxy-tyrosol that is the principal free phenol in the olive. It should be remembered that, depending on the olive cultivar, the oleuropein can be prevalent against the comoside, or it could be the contrary, until reaching the equality. 

Pharmacological studies were mainly focussed on oleuropein that represents die key phenolic compound in O. europaea, and on related phenolic compounds such as tyrosol and hydroxy-tyrosol. Therefore, the following discussion will be focussed on reported biological activity of these compounds. 

---