Journal of Food Bioactives, ISSN 2637-8752 print, 2637-8779 online
Journal website www.isnff-jfb.com

Review

Volume 11, September 2020, pages 31-56

A review of the evolution in the research of antioxidants in olives and olive oil during the last four decades

Figures

Figure 1.
Figure 1. Unsaponifiable fraction of olive oil (Kiritsakis, 1998).
Figure 2.
Figure 2. Main phenolic substances in olive oil.
Figure 3.
Figure 3. Oleocanthal, oleacein, oleuropein aglycon, ligstroside aglycon, oleocanthal + oleacein (D3) and total phenolic secoiridoids of olive oil enriched by replacing water in a three-phase decanter system with 0 (control), 50 or 100% OMWW (values within the same letter are not significantly different at 0.05) (Kiritsakis et al., 2017b).
Figure 4.
Figure 4. 1H NMR spectrum of the aldehydic region of Mission olive oil extract sample (a: up) and typical Koroneiki (b: down) showing the peaks corresponding to compounds 3–10 (Melliou et al., 2015, 2017).
Figure 5.
Figure 5. Changes in tomato sauce phenolics from VOO addition over time, using two different concentrations of VOO (5 and 10%) (Tresserra-Rimbau and Lamuela-Raventós, 2017).
Figure 6.
Figure 6. Polyphenols activities in human bodies. Source: Kindly granted by Luigi Iorio, E. (2020)

Tables

Table 1. Most important classes of phenolic compounds in olive fruits
 
Phenolic groupCompounds
Source: Adapted from Ghanbari et al. (2012).
AnthocyaninsCyanidin-3-glycoside, cyanidin-3-rutinoside, cyanidin-3-caffeyglycoside, cyanidin-3-caffeylrutinoside, delphinidin 3-rhamosylglycoside-7-xyloside
Flavonols and flavonesApigenin-7-glycoside, luteolin-7-rutinoside, luteolin-7-glycoside, luteolin-5-glycoside, quercetin-3-rutinoside
Phenolic acidsChlorogenic acid, caffeic acid, p-hydroxybenzoic acid, protocatechuic acid, vanillic acid, syringic acid, p-coumaric acid, o-coumaric acid, ferulic acid, sinapic acid, benzoic acid, cinnamic acid, gallic acid
Phenolic alcohols(3,4-Dihydroxyphenyl) ethanol (3,4-DHPEA), (p-hydroxyphenyl) ethanol (p-HPEA)
SecoiridoidsOleuropein, demethyloleuropein, ligstroside, nuzhenide hydroxycinnamic acid derivatives verbascoside

 

Table 2. Concentration of different polyphenol classes measured in olives and olive oil (mg/kg)
 
Olives and Olive Oil samplesPolyphenol Class
FlavonoidsLignansPhenolic acidsOther polyphenols
“Refined” oils are deodorized, neutralized and degummed. Concentrations expressed as mg/kg (mean ± standard deviation). *Chromatography after hydrolysis. Data from www.phenol-explorer.eu (accessed Nov. 18th 2019).
Black olives, raw1,598 ± 25000.7 ± 00.1*3,075 ± 199*2,658 ± 340
Green olives, raw05.6 ± 03.100.4 ± 00.1*2,205 ± 134*2,110 ± 260
Extra virgin olive oil15.3 ± 05.710.8 ± 01.703.1 ± 00.2595 ± 80
Virgin olive oil02.3 ± 00.228.1 ± 13.605.3 ± 00.4541 ± 44
Refined olive oil01.5 ± 00.631.6 ± 11.7n.d.336 ± 39

 

Table 3. Phenolic compounds of olive oil
 
Phenolic GroupCompounds
Source: Adapted from Romani et al. (2019).
Benzoic acid and Derivatives3-Hydroxybenzoic acid; p-Hydroxybenzoic acid; 3,4-Dihydroxybenzoic acid; Gentisic acid; Vanillic acid; Gallic acid; Siringic acid
Cinnamic acid and Derivativeso-Coumaric acid; p-Coumaric acid; Caffeic acid; Ferulic acid; Sinapinic acid
Other Phenolic Acids and Derivativesp-Hydroxyphenylacetic acid; 3,4-Dihydroxyphenylacetic acid; 4-Hydroxy-3-methoxyphenylacetic acid; 3-(3,4-Dihydroxyphenyl)propanoic acid
Phenyl Ethyl AlcoholsTyrosol [(p-hydroxyphenyl)ethanol] or p-HPEA; Hydroxytyrosol [(3,4-dihydroxyphenyl)ethanol] or 3,4-DHPEA
Aglycons SecoiridoidsOleuropein aglycon or 3,4-DHPEA-EA; Ligstroside aglycon or p-HPEA-EA; Aldehydic form of oleuropein aglycon; Aldehydic form of ligstroside aglycon
Dialdehydic Forms of SecoiridoidsDecarboxymethyl ligstroside aglycon (3,4-DHPEA-EDA); Decarboxymethyl oleuropein aglycon (p-HPEA-EDA)
Flavonols(+)-taxifolin
FlavonsApigenin; Luteolin
Lignans(+)-Pinoresinol; (+)-1-Acetoxypinoresinol; (+)-1-Hydroxypinoresinol
Hydroxyisochromans1-Phenyl-6,7-dihydroxy-isochroman; 1-(3′Methoxy-4′hydroxy)phenyl-6,7-dihydroxy-isochroman

 

Table 4. Animal studies regarding the bioavailability of olive and olive oil phenolics in humans
 
TreatmentSubjectsDose of phenolicsDesignResultsReference
4 VOO (A, B, C, D)6 male healthy volunteers (27–33 years)50 mL samples, A: 487.5 mg/L, B: 975 mg/L, C: 1,462.5 mg/L, D: 1,950 mg/L4 single doses, urine sampling for 24 hHT and T were dose-dependently absorbed and excreted in urine mainly as glucuronide conjugates. Only 30–60% of HT and 20–22% of T excreted in urine. Urinary excretion of HT metabolites, homovanillic alcohol and homovanillic acid, correlated with the dose of administered HTVisioli et al., 2000; Caruso et al., 2001
EVOO8 healthy volunteers (3 women and 5 men, 25–52 years)50 mL sample, 1,650 μg T/50 mLSingle dose, urine sampling for 24 hT was excreted mainly in its conjugated form. Only 6–11% of T in urine was in its free form. Recovery of T at 24 h was 17–43%Miro-Casas et al., 2001a
VOO11 healthy volunteers (6 women and 5 men, 25–65 years)50 mL sample, 1,055 μg HT/50 mL, 655 μg T/50 mLSingle dose, urine sampling for 24 hHT and T are mainly excreted in conjugated form; only 5.9% of HT and 13.8% of T were in free form. Recovery of HT and T at 24 h was 32–98 and 12–32%, respectivelyMiro-Casas et al., 2001b
3 supplements containing olive oil phenolics20 healthy volunteers (12 women and 8 men, 20–75 years)100 mg of samples with HT, L, OE, T3 single doses, ileostomy effluent and urine sampling for 24 h55–66% of ingested olive oil phenolics are absorbed, and 5–16% is excreted as HT and T in urineVissers et al., 2002
VOO6 healthy volunteers (3 women and 3 men, 25–47 years)25 mL sample, 49.3 mg HT/LSingle dose, plasma sampling for 8 h and urine sampling for 12 h≈98% of HT was present in plasma and urine in conjugated forms, mainly glucuronoconjugatesMiro-Casas et al., 2003
3 VOO (L, M, H)12 male healthy volunteers (20–22 years)40 mL samples, L: 10 mg/kg, M: 133 mg/kg; H: 486 mg/kg3 single doses, urine sampling for 24 hHT and T were dose-dependently absorbedWeinbrenner et al., 2003
3 VOO (L, M, H)12 male healthy volunteers (20–22 years)40 mL samples, L: 2.7 mg/kg, M: 164 mg/kg; H: 366 mg/kg3 single doses, plasma sampling for 24 hHT and T were dose-dependently absorbedCovas et al., 2006
2 EVOO (L, H)10 postmenopausal Women (47–67 years)50 g samples, L: 147 mg/kg, H: 592 mg/kg8 weeks crossover 50 g per day Urine sampling for 24 hUrinary excretion of HT and its metabolite homovanillyl alcohol were significantly increased in subjects consuming high EVOOSalvini et al., 2006
20 olives8 male healthy volunteers (30–40 years)≈100 g sample, 76.73 mg HT/100 g, 19.48 mg T/100 gSingle dose, blood sampling for 4 h, urine sampling for 24 hHT and T appeared in plasma and urine, mainly as glucuronidesKountouri et al., 2007
EVOO10 healthy volunteers (5 women and 5 men, 24–35 years)50 mL sampleSingle dose, urine sampling for 6 hTentative identification of more than 60 metabolites of olive oil polyphenols was achievedGarcia-Villalba et al., 2010
HT supplement10 healthy volunteers (2 women and 8 men, 22–34 years)2.5 mg HT/kg weightSingle dose, blood sampling for 120 min, urine sampling for 24 hHVA was detected in plasma. The main metabolites in urine were HVA (31%), DHPA glucuronide (22.7%), and 5% free or conjugated HTGonzalez-Santiago et al., 2010
VOO11 healthy volunteers (5 women and 6 men, 20–44 years)50 mL sample, 21.96 μmol HT/50 mL, 15.20 μmol T/50 mL, 0.27 μmol HVA/50 mLSingle dose, plasma and urine, sampling for 24 h13% of the olive oil polyphenols were recovered in urine, where 75% of them were glucuronides and 25% as free compoundsKhymenets et al., 2011
VOO vs. PEVOO13 healthy volunteers (6 women and 7 men, 25–69 years)30 mL samples, VOO: 288.89 mg/kg, PEVOO: 961.17 mg/kg2 single doses, blood sampling for 300 min24 compounds detected, mostly secoiridoids and phenol alcohol groups in sulfated and glucuronidated forms. 14 out of 24 compounds were higher in samples of PEVOO compared to VOOSuarez et al., 2011
3 PEVOO (L, M,
H)		12 healthy volunteers (6 women and 6 men, 22–60 years)30 mL samples, L: 250 mg/kg, M: 500 mg/kg, H: 750 mg/kg3 single doses, plasma sampling for 360 minDose-dependent responses of phenol conjugates were obtained in plasma. Hydroxytyrosol acetate sulfate was identified as the main biological metabolite of HT from olive oil ingestionRubio et al., 2012a; 2012b
EVOO45 healthy volunteers (34 women and 11 men, 21–45 years)50 mL sample, 509.72 mg/L30 days crossover, twice (30+20 mL)/day, blood sampling on days 0 and 30.HT and its 3 metabolites, and T and its 2 metabolites, were identified in the plasmaOliveras-Lopez et al., 2014
Ordinary olive oil vs. EVOOA healthy male volunteer25 mL sample, ordinary: 19.7 mmol HT/oil, EVOO: 398.2 mmol HT/oilSingle dose, blood sampling for 4 hHigher HT levels were detected in EVOO, whereas HT levels in ordinary olive oil were undetectable. 0.3% of the administered dose of free HT was detected in plasmaPastor et al., 2016
HT capsules (A, B, C)21 male volunteersA: 25 mg HT/day, B: 5 mg HT/day, C: Placebo7 days treatment and 1 week wash-out, cross-over, urine sampling for 24 h21–28% of the HT and its metabolites (mainly HT-glucuronide 3′, 16.6–23.6%) were recovered in the urine. Interindividual variability was 10%Khymenets et al., 2016
Olive oil extract3 healthy volunteers (25–30 years)50 mL sample, 120 mg HT+OEBlood sampling for 120 min3 metabolites, namely HT-3-O-sulphate, HT acetate sulphate and homovanillic alcohol sulphate were idemtified in collected samplesLopez de las Hazas et al., 2016
EVOO9 healthy volunteers (6 women & 3 men, 24–61 years)50 mL sample, 322 mg phenolics/kg + 6 mg HT and derivatives/20 gSingle dose, plasma sampling for 6 h, urine sampling for 24 hPlasma and urinary secoiridoid compounds (oleuropein and ligstroside derivatives) were selected as biomarkersSilva et al., 2018