Oleuropein structure

Oleuropein structure was determined by Panizzi et ah [2] on the basis of the results obtained from an accurate degradation of this compound. Only the absolute configurations of C-l and C-5 remained undetermined, as the cis/trans configuration of C-8/C-9 double bond. 

Oleuropein (81), which may be isolated from several species of Oleaceae, has a role in the increase of a 50% of the coronary blood flew, and shows spasmolitic and antiarritmic effects [110]. On the other hand, it is known that elenolic acid, obtained by hydrolysis of the extracts of olive-tree leaves, has hypertensive properties. All this suggests that the glucoside ring and the 3,4-dihydroxyphenylethanol moieties, both talcing part of the oleuropein structure, but absent in the elenolic acid, are not responsible for the hypotensive activity. 

Secoiridoids are complex phenols produced from the secondary metabolism of terpenes as precursors of several indole alkaloids (Soler-Rivas and others 2000). They are characterized by the presence of elenolic acid, in its glucosidic or aglyconic form, in their molecular structure. Oleuropein, the best-known secoiridoid, is a heterosidic ester of elenolic acid and 3,4- dihydroxyphenylethanol containing a molecule of glucose, the hydrolysis of which yields elenolic acid and hydroxytyrosol (Soler-Rivas and others 2000). 

Fig. (2). Structure of the dialdehydic forms of elenolic acid linked to (3,4-dihydroxyphenyl)-ethanol (compound 1) and to (p-hydroxyphenyl)-ethanol (compound 2). Compound 3 is an isomer of oleuropein aglycone.

Before 1960, one of main components of olive, the oleuropein, was studied in Roma. Panizzi s research group established the structure of this monoterpene glucoside, die leader of the group, that only several years later was identified as secoiridoids. Panizzi s group has isolated two other compounds the oleuropeic acid that is a monocyclic monoterpene, and its saccharose derivative. 

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. 

Oleuropein 1 is the first secoiridoid whose structure was recognised in 1958-65[1-3], but only several years later it was classified as secoiridoid, when this class of monoterpenoids was constituted. 

In compound 24, oleuroside, a modification at the level of monoterpenoid unit is present. In fact, the C-8/C-9 double bond of oleuropein is shifted to C-8/C-10 position, as in the secologanin. The occurrence of 24 in O. europaea seems to be in contrast with the biogenetic trend of this plant that appears to be devoted to the a molecular structure that was classified as oleuropein-type [26,27],... 

Enzymatic hydrolysis of gfucosidic function allows to free aglycon that exists in different forms, which we revealed by following the hydrolysis of oleuropein 1 in NMR tube [42-43]. The hemiacetalic 35a structure (see Figure 17) is formed as a consequence of the hydrolysis of glucose that appeared to be in equilibrium with the dihaldeidic structure 35b. In the... 

The interaction observed between oleuropein and DMPC liposomes may be due to the introduction of lipophilic molecules into the ordered structure of the lipid bilayer [55]. 

The tables 1 - 7 contain the structures of the iridoids and secoiridoids from Oleaceae. The reference and the natural origin correspond to the first cite in which the compound has been named. In any case, secoiridoids such as oleuropein (81), ligustroside (82) and many others can be obtained from several species. 

Rios JJ, Gil MJ, Gutierrez-Rosales F (2005) Solid-phase extraction gas chrranatography-ion trap-mass spectrometry qualitative method for evaluation of phenolic compounds in virgin olive oil and structural confirmation of oleuropein and ligstroside aglyctnis and their oxidation products. J Chromatogr A 1093 167-176... 

Chemical Structure, Biosynthesis, and Enzymatic Degradation of Oleuropein. .. 3609... 

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