Comparison of the antioxidant activities of extra virgin olive oils.
The phenol content and antioxidant activity of extra virgin olive oils (EVOOs) differing in their origins and degradation degrees were studied. The o-diphenolic compounds typical of olive oil, namely, the oleuropein derivatives hydroxytyrosol (3',4'-dihydroxyphenylethanol, 3',4'-DHPEA), the dialdehydic form of elenolic acid linked to 3',4'-DHPEA (3',4'-DHPEA-EDA), and an isomer of oleuropein aglycon (3',4'-DHPEA-EA), were analyzed by HPLC. The antioxidant activity was studied by (a) the xanthine oxidase (XOD)/xanthine system, which generates superoxide radical and hydrogen peroxide; (b) the diaphorase (DIA)/NADH/juglone system, which generates superoxide radical and semiquinonic radical; and (c) the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) test. Results showed that EVOOs with a low degradation level (as evaluated by acidity, peroxide number, and spectroscopic indices K(232), K(270), and deltaK according to the EU Regulation) had a higher content of 3',4'-DHPEA-EDA and a lower content of 3',4'-DHPEA than oils having intermediate and advanced degradation levels. EVOOs with a low degradation degree were 3-5 times more efficient as DPPH scavengers and 2 times more efficient as inhibitors of the XOD-catalyzed reaction than oils with intermediate and advanced degradation levels. The DIA-catalyzed reaction was inhibited by EVOOs having low or intermediate degradation levels but not by the most degraded oils.
Lavelli
Vera
V
DISTAM, Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Universitá degli Studi di Milano, via Celoria 2, I-20133 Milano, Italy. vera.lavelli@unimi.it
D000975:Antioxidants / Q000032:analysis* / Q000494:pharmacology; D016227:Benzoquinones / Q000737:chemistry; D001713:Biphenyl Compounds; D002851:Chromatography, High Pressure Liquid; D008058:Dihydrolipoamide Dehydrogenase; D006861:Hydrogen Peroxide / Q000737:chemistry; D009285:Naphthoquinones; D000069463:Olive Oil; D010636:Phenols / Q000032:analysis / Q000494:pharmacology; D010851:Picrates / Q000737:chemistry; D010938:Plant Oils / Q000737:chemistry*; D013481:Superoxides / Q000737:chemistry; D019820:Xanthine; D014969:Xanthine Oxidase
D000975:Antioxidants; D016227:Benzoquinones; D001713:Biphenyl Compounds; D009285:Naphthoquinones; D000069463:Olive Oil; D010636:Phenols; D010851:Picrates; D010938:Plant Oils; D013481:Superoxides; D019820:Xanthine; C025232:semiquinone radicals; D006861:Hydrogen Peroxide; C004931:1,1-diphenyl-2-picrylhydrazyl; D014969:Xanthine Oxidase; D008058:Dihydrolipoamide Dehydrogenase; C005134:juglone