10-Hydroxy-oleuropein

Acetonyl-7-hydroxy-5-methyl-6-sophorosylchromone, in A-20020 10-Hydroxy oleuropein, in 0-10033... 

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. 

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. 

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. 

Compound 22, ligstroside, is very similar to oleuropein from which it differs for the presence of a tyrosol unit instead of hydroxy-tyrosol [24]. 

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. 

Oleuropein and hydroxy-tyrosol, derived from oleuropein hydrolysis [46], possess several biological properties certainly mediated by their antioxidant and free radical-scavenging ability (antimicrobial, hypotensive, vasodilatator and hypoglycaemic activities) [47],... 

The antioxidative effect of oleuropein and hydroxy-tyrosol (see Fig 20) was investigated by Saija et al. [51], in a model system consisting of dipalmitoyl-phosphatidyl-eholine/Unoleic acid unilamellar vesicles and a water-soluble azo-compound as a free radical generator. 

Oleuropein appears to interfere with some biological processes such as lipoprotein oxidation, platelet aggregation, platelet and leukocyte eicosanoid production and cardiovascular control too. As previously described, oleuropein and hydroxy-tyrosol are characterised by a catechol moiety that appears to be needed for their scavenger and antioxidant activities. In fact, it was demonstrated that these compounds prevent thermally initiated autoxidation of methyl linoleate in homogenous solutions [56], protect LDL from oxidation [57] and inhibit production of... 

The free radical-scavenging capacity of oleuropein and hydroxy-tyrosol was tested, using some radical generators. As a radical initiator, AAPH 2,2 -azobis (2-amidinopropane)-hydrochloride) was used for peroxyl radicals generation, because it is a common free radical found in the body [59] and has often been used in several antioxidant activity assays [60]. It appears to be slightly less reactive than OH-radical [61]. 

Other experimental studies carried out with a different radical, DPPH (7, l-diphenyl-2-picrylhydrazyl radical), revealed that oleuropein and hydroxy-tyrosol elicit a good, concentration-dependent, scavenging effect... 

Incubation of DPPC/LA idipalmitoylphosphatidylcholine/linoleic acid) LUV with AAPH increased the accumulation of LOOH (linoleic peroxy acid) formed from LA peroxidation. When the tested biphenols were added, a reduction in the amount of LOOH formed was observed and thus oleuropein proved more effective than hydroxy-tyrosol [62]. 

The cited works demonstrated that oleuropein and hydroxy-tyrosol are potent antioxidants against lipid peroxidation in phospholipid bilayers, induced by aqueous oxygen radicals. These results may be very interesting, because biphenols could have important applications in human diseases caused by free radical damage. 

These results showed that oleuropein has a good antioxidative activity. The beneficial health effects of Mediterranean diet are probably related to non-nutrient components present in foods, such as olive oil, as well as wine and others. In fact, oleuropein and hydroxy-tyrosol, both green and black tea components and gallic acid inhibit androstenedione 6-p-hydroxylase activity. 

Some results evidenced that human CYP3A have a very good capacity to generate reactive oxygen species therefore, there were interesting results in examining the effects of dietary phenols, such as oleuropein and hydroxy-tyrosol, known CYP3 A inhibitors [69],... 

Hydroxy-tyrosol (DPE 3,4-dihydroxyphenylethanol) is a liposoluble and hydrosoluble compound present in high concentration in extra virgin olive oil, in free or esterified form, such as oleuropein aglycone [42-43]. 

LLE Hexane 60% aqueous MeOH MeOH/H O (1 1 v/v) Tyrosol, 2.3-dihydroxyphenylethanol, oleuropein glycoside, hydroxytyrosol, dihydrocaffeic acid, cinnamic acid, 4-hydroxy-phenylacetic acid, gentisic acid, taxifolin, syringic acid, ferulic acid, luteolin, o-coumaric acid, p-coumaric acid, quercetin, vanillic acid, 4-hydroxy-benzoic acid, caffeic acid, 3,4-dihydroxyphenylacetic acid, gallic acid, and protocatechuic acid UV-vis (200 nm) ESI-MSD CZE-DAD HPLC... 

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