title: Antioxidant synergy and regeneration effect of quercetin, (-)-epicatechin, and (+)-catechin on alpha-tocopherol in homogeneous solutions of peroxidating methyl linoleate.
abstract: Antioxidant interactions between flavonoids and alpha-tocopherol have been demonstrated by oximetry (oxygen concentration measured by ESR signal line width). In tert-butyl alcohol, a solvent in which flavonoids are weak retarders of peroxidation of methyl linoleate when initiated by alpha,alpha'-azoisobutyronitrile, quercetin and (-)-epicatechin were found to act synergistically with the chain-breaking antioxidant alpha-tocopherol. In chlorobenzene, a solvent in which flavonoids are chain-breaking antioxidants, quercetin and (+)-catechin each regenerated alpha-tocopherol, resulting in a co-antioxidant effect. The stoichiometric factor of the flavonoids as chain-breaking antioxidants in 1:1 mixtures with alpha-tocopherol was measured to be close to 1 for quercetin and slightly smaller for the catechins. The apparent inhibition rate constant, k(inh), for the mixture quercetin/alpha-tocopherol was measured to be 4.1 x 10(5) and 2.6 x 10(6) M(-1) s(-1) in tert-butyl alcohol and chlorobenzene, respectively, at 50 degrees C. A k(inh) of 4.4 x 10(5) M(-1) s(-1) was measured for (+)-catechin alone in chlorobenzene at 50 degrees C.
authors.affiliation: Food Chemistry, Department of Dairy and Food Science, Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark. pap@kvl.dk
authors.forename: Pamela
authors.initials: P
authors.lastname: Pedrielli
authors.forename: Leif H
authors.initials: LH
authors.lastname: Skibsted
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology*; D002392:Catechin / Q000737:chemistry / Q000494:pharmacology*; D002722:Chlorobenzenes; D004357:Drug Synergism; D004578:Electron Spin Resonance Spectroscopy; D008041:Linoleic Acids / Q000737:chemistry*; D010084:Oxidation-Reduction; D011794:Quercetin / Q000737:chemistry / Q000494:pharmacology*; D012996:Solutions; D012997:Solvents; D024502:alpha-Tocopherol / Q000737:chemistry / Q000494:pharmacology*; D020002:tert-Butyl Alcohol
chemical_list: D000975:Antioxidants; D002722:Chlorobenzenes; D008041:Linoleic Acids; D012996:Solutions; D012997:Solvents; C005575:methyl linoleate; D002392:Catechin; D011794:Quercetin; D024502:alpha-Tocopherol; C031294:chlorobenzene; D020002:tert-Butyl Alcohol