title: Activity and location of olive oil phenolic antioxidants in liposomes.
abstract: The antioxidant activity of hydroxytyrosol, hydroxytyrosol acetate, oleuropein, 3,4-dihydroxyphenylelenolic acid (3,4-DHPEA-EA) and 3,4-dihydroxyphenylelenolic acid dialdehyde (3,4-DHPEA-EDA) towards oxidation initiated by 2,2'-azobis(2-amidinopropane) hydrochloride in a soybean phospholipid liposome system was studied. The antioxidant activity of these olive oil phenols was similar and the duration of the lag phase was almost twice that of alpha-tocopherol. Trolox, a water-soluble analogue of alpha-tocopherol, showed the worst antioxidant activity. However, oxidation before the end of the lag phase was inhibited less effectively by the olive oil phenols than by alpha-tocopherol and Trolox. Synergistic effects (11-20% increase in lag phase) were observed in the antioxidant activity of combinations of alpha-tocopherol with olive oil phenols both with and without ascorbic acid. Fluorescence anisotropy of probes and fluorescence quenching studies showed that the olive oil phenols did not penetrate into the membrane, but their effectiveness as antioxidants showed they were associated with the surface of the phospholipid bilayer.
authors.affiliation: Departamento de Química, Centro de Investigação em Química, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, no 687, 4169-007 Porto, Portugal. mpmartin@fc.up.pt
authors.forename: Fátima
authors.initials: F
authors.lastname: Paiva-Martins
authors.forename: Michael H
authors.initials: MH
authors.lastname: Gordon
authors.forename: Paula
authors.initials: P
authors.lastname: Gameiro
mesh_terms: D000578:Amidines / Q000737:chemistry; D000975:Antioxidants / Q000032:analysis* / Q000737:chemistry; D001205:Ascorbic Acid / Q000032:analysis / Q000737:chemistry; D052160:Benzothiazoles; D002839:Chromans / Q000032:analysis / Q000737:chemistry; D005454:Fluorescence Polarization; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry*; D008560:Membrane Fluidity; D000069463:Olive Oil; D010084:Oxidation-Reduction; D010636:Phenols / Q000032:analysis / Q000737:chemistry*; D010938:Plant Oils / Q000032:analysis / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry; D013451:Sulfonic Acids / Q000032:analysis / Q000737:chemistry; D024502:alpha-Tocopherol / Q000032:analysis / Q000737:chemistry
chemical_list: D000578:Amidines; D000975:Antioxidants; D052160:Benzothiazoles; D002839:Chromans; D008081:Liposomes; D000069463:Olive Oil; D010636:Phenols; D010938:Plant Oils; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C046728:2,2'-azobis(2-amidinopropane); D024502:alpha-Tocopherol; D001205:Ascorbic Acid; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid