title: Finding of synergistic and cancel effects on the aroxyl radical-scavenging rate and suppression of prooxidant effect for coexistence of α-tocopherol with β-, γ-, and δ-tocopherols (or -tocotrienols).
abstract: Measurements of aroxyl radical (ArO•)-scavenging rate constants (k(s)(AOH)) of antioxidants (AOHs) [α-, β-, γ-, and δ-tocopherols (TocHs) and -tocotrienols (Toc-3Hs)] were performed in ethanol solution via stopped-flow spectrophotometry. k(s)(AOH) values of α-, β-, γ-, and δ-Toc-3Hs showed good agreement with those of the corresponding α-, β-, γ-, and δ- TocHs. k(s)(AOH) values were measured not only for each antioxidant but also for mixtures of two antioxidants: (i) α-TocH with β-, γ-, or δ-TocH and (ii) α-TocH with α-, β-, γ-, or δ-Toc-3H. A synergistic effect in which the k(s)(AOH) value increases by 12% for γ-TocH (or by 12% for γ-Toc-3H) was observed for solutions including α-TocH and γ-TocH (or γ-Toc-3H). On the other hand, a cancel effect in which the k(s)(AOH) value decreases (a) by 7% for β-TocH (or 11% for β-Toc-3H) and (b) by 24% for δ-TocH (or 25% for δ-Toc-3H) was observed for solutions including two kinds of antioxidants. However, only a synergistic effect may function in edible oils, because contents of β- and δ-TocHs (and β- and δ-Toc-3Hs) are much less than those of α- and γ-TocHs (and α- and γ-Toc-3Hs) in many edible oils. UV-vis absorption of α-Toc•, which was produced by reaction of α-TocH with ArO•, decreased remarkably for coexistence of α-TocH with β-, γ-, or δ-TocH (or β-, γ-, or δ-Toc-3H), indicating that the prooxidant effect of α-Toc• is suppressed by the coexistence of other TocHs and Toc-3Hs.
authors: Department of Chemistry, Faculty of Science, Ehime University , Matsuyama 790-8577, Japan.
authors: Aya
authors: A
authors: Ouchi
authors: Shin-ichi
authors: S
authors: Nagaoka
authors: Tomomi
authors: T
authors: Suzuki
authors: Katsuhiro
authors: K
authors: Izumisawa
authors: Taisuke
authors: T
authors: Koike
authors: Kazuo
authors: K
authors: Mukai
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology*; D004336:Drug Antagonism; D004357:Drug Synergism; D000431:Ethanol / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry / Q000494:pharmacology*; D007700:Kinetics; D009994:Osmolar Concentration; D016877:Oxidants / Q000819:agonists / Q000037:antagonists & inhibitors / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry; D013237:Stereoisomerism; D024505:Tocopherols / Q000819:agonists / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D024508:Tocotrienols / Q000819:agonists / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D016877:Oxidants; D017382:Reactive Oxygen Species; D012997:Solvents; D024508:Tocotrienols; D000431:Ethanol; D024505:Tocopherols