title: Inhibition of the metmyoglobin-induced peroxidation of linoleic acid by dietary antioxidants: Action in the aqueous vs. lipid phase.
abstract: The gastric digestion of food containing oxidizable lipids and iron catalysts for peroxide decomposition such as (met)myoglobin from muscle meat can be accompanied by an extensive formation of potentially toxic lipid hydroperoxides. An early protective action by dietary antioxidants in the gastro-intestinal tract is plausible, especially for poorly bioavailable antioxidants such as polyphenols. Hence, the ability of antioxidants to inhibit lipid peroxidation initiated by dietary iron in mildly acidic emulsions is a valuable and general model. In this work, the ability of some ubiquitous dietary antioxidants representative of the main antioxidant classes (alpha-tocopherol, the flavonol quercetin, beta-carotene) to inhibit the metmyoglobin-induced peroxidation of linoleic acid is investigated by UV-visible spectroscopy and HPLC in mildly acidic emulsions. The phenolic antioxidants quercetin and alpha-tocopherol come up as the most efficient peroxidation inhibitors. Inhibition by quercetin essentially proceeds in the aqueous phase via a fast reduction of an unidentified activated iron species (with a partially degraded heme) produced by reaction of metmyoglobin with the lipid hydroperoxides. This reaction is faster by, at least, a factor 40 than the reduction of ferrylmyoglobin (independently prepared by reacting metmyoglobin with hydrogen peroxide) by quercetin. By contrast, alpha-tocopherol mainly acts in the lipid phase by reducing the propagating lipid peroxyl radicals. The poorer inhibition afforded by beta-carotene may be related to both its slower reaction with the lipid peroxyl radicals and its competitive degradation by autoxidation and/or photo-oxidation.
authors.affiliation: UMR A 408 INRA-University of Avignon, Safety and Quality of Plant Products, Site Agroparc, Domaine St-Paul, 84914 Avignon Cedex 9, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Vulcain
authors.forename: Pascale
authors.initials: P
authors.lastname: Goupy
authors.forename: Catherine
authors.initials: C
authors.lastname: Caris-Veyrat
authors.forename: Olivier
authors.initials: O
authors.lastname: Dangles
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D004032:Diet; D006736:Horses; D006863:Hydrogen-Ion Concentration; D019787:Linoleic Acid / Q000378:metabolism*; D015227:Lipid Peroxidation / Q000187:drug effects*; D008786:Metmyoglobin / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D010084:Oxidation-Reduction; D011794:Quercetin / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism; D013057:Spectrum Analysis; D024502:alpha-Tocopherol / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D017382:Reactive Oxygen Species; D008786:Metmyoglobin; D011794:Quercetin; D019787:Linoleic Acid; D024502:alpha-Tocopherol