Antioxidant effect of phenolic compounds, alpha-tocopherol, and other minor components in virgin olive oil.
The effect of acidity, squalene, hydroxytyrosol, aldehydic form of oleuropein aglycon, hydroxytyrosyl acetate, tyrosol, homovanillic acid, luteolin, apigenin, alpha-tocopherol, and the mixtures hydroxytyrosol/hydroxytyrosyl acetate, hydroxytyrosol/tyrosol, and hydroxytyrosol/alpha-tocopherol on the oxidative stability of an olive oil matrix was evaluated. A purified olive oil was spiked with several concentrations of these compounds and, then, subjected to an accelerated oxidation in a Rancimat apparatus at 100 degrees C. Acidity, squalene, homovanillic acid, and apigenin showed negligible effect. At the same millimolar concentrations, the different o-diphenolic compounds yielded similar and significant increases of the induction time, alpha-tocopherol a lesser increase, and tyrosol a scarce one. At low concentrations of o-diphenols and alpha-tocopherol, a linear relationship between induction time and concentration was found, but at high concentrations the induction time tended toward constant values. To explain this behavior, a kinetic model was applied. The effect of the mixtures hydroxytyrosol/hydroxytyrosyl acetate was similar to that of a single o-diphenol at millimolar concentration equal to the sum of millimolar concentrations of both compounds. Concentrations of tyrosol >0.3 mmol/kg increase the induction time by 3 h. The mixtures hydroxytyrosol/alpha-tocopherol showed opposite effects depending on the relative concentrations of both antioxidants; so, at hydroxytyrosol concentrations <0.2 mmol/kg, the addition of alpha-tocopherol increased the induction time, whereas at higher hydroxytyrosol concentrations, the alpha-tocopherol diminished the stability.
Mateos
Raquel
R
Instituto de la Grasa (CSIC), Avenida Padre García Tejero 4, E-41012 Seville, Spain.
Domínguez
Manuel M
MM
Espartero
José Luis
JL
Cert
Arturo
A
D000975:Antioxidants / Q000494:pharmacology*; D004355:Drug Stability; D005227:Fatty Acids / Q000032:analysis; D005419:Flavonoids / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D019301:Oleic Acid / Q000494:pharmacology; D000069463:Olive Oil; D010084:Oxidation-Reduction; D010636:Phenols / Q000494:pharmacology*; D010938:Plant Oils / Q000737:chemistry*; D013185:Squalene / Q000494:pharmacology; D024502:alpha-Tocopherol / Q000494:pharmacology*
D000975:Antioxidants; D005227:Fatty Acids; D005419:Flavonoids; D000069463:Olive Oil; D010636:Phenols; D010938:Plant Oils; D019301:Oleic Acid; D013185:Squalene; D024502:alpha-Tocopherol