The Mediterranean Sea basin is the main olive-producing region all over the world. Greece constitutes one of the most important countries in olive culture, accounting for 13% and 5.3% of the global olive oil and table olive production, respectively (International Olive Oil Council, 2011). There are ≈60 olive tree cultivars originating from Greece, some of which are cultivated globally (i.e., ‘Koroneiki’, ‘Kalamon’), whereas most of them are found in local areas.
Phenolic compounds are secondary metabolites with a great structural diversity and a wide phylogenetic distribution (Harborne, 1989). Phenolic compounds influence the organoleptic properties of olive fruits and virgin olive oils and are important markers for studying fruit characteristics of different cultivars and controlling olive production processes. Their antioxidant effect is correlated to the high stability of virgin olive oil against heat oxidation and autoxidation processes overtime (Romani et al., 1999). Besides fruits, some studies considered the phenol fraction present in olive leaves (Briante et al., 2002b; Ranalli et al., 2006). Olive leaves are endowed with the most potent free radical scavenging power among the different parts of olive trees and provide considerable amounts of high added-value compounds (Japón-Luján et al., 2006). Olive leaves have phenol composition similar to that of olive fruit with oleuropein constituting the main phenolic compound followed by other phenol glycosides (Benavente-García et al., 2000).
Oleuropein is a heterosidic ester of β-glucosylated elenolic acid and hydroxytyrosol and can be easily transformed by endogenous or exogenous supply of the enzyme β-glucosidase into glucose and oleuropein aglycon (Ranalli et al., 2006). It is also the most abundant phenolic compound in olive leaves and fruits and is considered as the main responsible factor for the characteristic bitterness of olive fruit and the browning that occurs in green table olives either after impact and wounding during harvesting or during subsequent technological treatments (Malik and Bradford, 2006; Soler-Rivas et al., 2000; Therios, 2009). Health benefits of oleuropein have been extensively investigated. Specifically, it has been reported that oleuropein and other related phenolic compounds such as hydroxytyrosol, tyrosol, verbascoside, ligustroside, and demethyloleuropein act as antioxidants that contribute to a lower risk of coronary diseases (Beauchamp et al., 2005; Visioli et al., 1998; Wiseman et al., 1996) and several types of cancers (Owen et al., 2000; Tripoli et al., 2005). Furthermore, these compounds present antimicrobial and antiviral activity (Bisingnano et al., 1999; Uccella, 2001).
The chemical and biochemical composition of olives relies on some agronomical factors, one of which is the cultivar. Because phenolic compounds play an important role in olive fruit and virgin olive oil quality and present several health benefits, the aim of the present study was to determine the phenolic content and fruit antioxidant activity of 11 Greek olive cultivars. This is of great importance to explore phenolic concentration of the previously mentioned cultivars and identify those with high values to use them commercially for oleuropein production.
BeauchampG.K.KeastR.S.J.MorelD.LinJ.PikaJ.HanQ.LeeC.H.SmithA.B.BreslinP.A.S.2005Phytochemistry: Ibuprofen-like activity in extra-virgin olive oilNature4374546
Benavente-GarcíaO.CastilloJ.LorenteJ.OrtuñoA.Del RioJ.A.2000Antioxidant activity of phenolics extracted from Olea europaea L. leavesFood Chem.68457462
BenzieI.StrainJ.1996The ferric reducing ability of plasma (FRAP) as a measure of ‘antioxidant power’: The FRAP assayAnal. Biochem.2397076
BisingnanoG.TomainoA.Lo CascioR.CrisafiG.UccellaN.SaijaA.1999On the in vitro antimicrobial activity of oleuropein and hydroxytyrosolJ. Pharm. Pharmacol.51971974
BouazizM.JemaiH.KhabouW.SayadiS.2010Oil content, phenolic profiling and antioxidant potential of Tunisian olive drupesJ. Sci. Food Agr.9017501758
BrianteR.LacaraF.FebbraioF.PatumiM.NucciR.2002aBioactive derivatives from oleuropein by a biotransformation on Olea europaea leaf extractsJ. Biotechnol.93109119
BrianteR.PatumiM.LimongelliS.FebbraioF.VaccaroC.Di SaleA.La CaraF.NucciR.2002bChanges in phenolic and enzymatic activities content during fruit ripening in two Italian cultivars of Olea europaea LPlant Sci.162791798
DamakN.BouazizM.AyadiM.SayadiS.DamakM.2008Effect of the maturation process on the phenolic fractions, fatty acids, and antioxidant activity of the Chétoui olive fruit cultivarJ. Agr. Food Chem.5615601566
HarborneJ.B.1989General procedures and measurement of total phenolics p. 2–9. In: Dey P.M. and J.B. Harborne (eds.). Methods in plant phenolics. Academic Press London UK.
International Olive Oil Council2011Olive oil figures. 9 Nov. 2011. <http://www.internationaloliveoil.org/>.
Japón-LujánR.Ruise-JiménezJ.Luque De CastroM.D.2006Discrimination and classification of olive tree varieties and cultivation zones by biophenol contentsJ. Agr. Food Chem.5497069712
MalikN.S.A.BradfordJ.M.2006Changes in oleuropein levels during differentiation and development of floral buds in ‘Arbequina’ olivesSci. Hort.110274278
MorellóJ.R.RomeroM.P.MotilvaM.J.2004Effect of the maturation process of the olive fruit on the phenolic fraction of drupes and oils from Arbequina, Farga, and Morrut cultivarsJ. Agr. Food Chem.5260026009
Ortega-GarcíaF.PeragónJ.2009Phenylalanine ammonia-lyase, polyphenol oxidase, and phenol concentration in fruits of Olea europaea L. cv. Picual, Verdial, Arbequina, and Frantoio during ripeningJ. Agr. Food Chem.571033110340
OwenR.W.GiacosaA.HullW.E.HaubnerR.SpiegelhalderB.BartschH.2000The antioxidant/anticancer potential of phenolic compounds isolated from olive oilEur. J. Cancer3612351247
RanalliA.ContentoS.LuceraL.Di FeboM.MarchegianiD.Di FonzoV.2006Factors affecting the contents of iridoid oleuropein in olive leaves (Olea europaea L.)J. Agr. Food Chem.54434440
RanalliA.GomesT.DelcuratoloD.ContentoS.LuceraL.2003Improving virgin olive oil quality by means of innovative extracting biotechnologiesJ. Agr. Food Chem.5125972602
RanalliA.LuceraL.ContentoS.SimoneN.Del ReP.2004Bioactive constituents, flavors and aromas of virgin olive oils obtained by processing olives with a natural enzyme extractEur. J. Lipid Sci. Technol.106187197
RanalliA.MarchegianiD.ContentoS.GirardiF.NicolosiM.P.BrulloM.D.2009Variations of iridoid oleuropein in Italian olive varieties during growth and maturationEur. J. Lipid Sci. Technol.111678687
RomaniA.MulinacciN.PinelliP.VincieriF.F.CimatoA.1999Polyphenolic content in five Tuscany cultivars of Olea europaea LJ. Agr. Food Chem.47964967
ŠkergetM.KotnikP.HadolinM.Rižner HrašA.SimoničM.KnezŽ.2005Phenols, proanthocyanidins, flavones and flavonols in some plant materials and their antioxidant activitiesFood Chem.89191198
TheriosI.N.2009Olives. Crop Production Science in Horticulture Series. CABI UK. p. 409.
TripoliE.GiammancoM.TabacchiG.Di MajoD.GiammancoS.La GuardiaM.2005The phenolic compounds of olive oil: Structure, biological activity and beneficial effects on human healthNutr. Res. Rev.1898112
UccellaN.2001Olive biophenols: Biomolecular characterization, distribution and phytoalexin histochemical localization in the drupesTrends Food Sci. Technol.11315327
VignaA.F.FerreresF.SilvaB.M.ValentãoP.GonçalvesA.PereiraJ.A.OliveiraM.B.SeabraR.M.AndradeP.B.2005Phenolic profiles of Portuguese olive fruits (Olea europaea L.): Influences of cultivar and geographical originFood Chem.89561568
VisioliS.A.BellostaS.GalliC.1998Oleuropein, the bitter principle of olives, enhances nitric oxide production by mouse macrophagesLife Sci.62541546
WisemanS.A.MathotJ.De FouwN.J.TijburgL.B.M.1996Dietary non-tocopherol antioxidants present in extra virgin olive oil increase the resistance of low density lipoproteins to oxidation in rabbitsAtherosclerosis12012