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Kinetic study of quenching reactions of singlet oxygen and scavenging reactions of free radicals by α‐, β‐, λ‐ and σ‐tocopheramines in ethanol solution and micellar dispersion
Author(s) -
Itoh Shingo,
Nagaoka Shinichi,
Mukai Kazuo,
Ikesu Satoru,
Kaneko Yutaka
Publication year - 1994
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02536703
Subject(s) - chemistry , singlet oxygen , quenching (fluorescence) , radical , photochemistry , scavenging , oxygen , singlet state , phenols , antioxidant , organic chemistry , fluorescence , excited state , physics , nuclear physics , quantum mechanics
Quenching reactions of singlet oxygen and scavenging reactions of free radicals by α‐, β‐, λ‐ and σ‐tocopheramines (Toc‐amines) were investigated spectrophotometrically in ethanol and Triton X‐100 micellar dispersions. The rate constants of quenching of singlet oxygen ( k Q ) by α‐, β‐, λ‐ and σ‐Toc‐amines increased as the total electron donating capacity of the methyl groups at the aromatic ring increased. A plot of log k Q vs. peak oxidation potential ( E p ) was found to be linear and the slope was negative. Similar results were obtained for scavenging of a phenoxyl radical (PhO.). The results suggest that charge transfer plays an important role in these reactions. The k Q values were found to be 1.30–2.57 times as large as k Q for α‐tocopherol (α‐Toc). Although α‐Toc has the highest antioxidant activity among natural tocopherols and related phenols, Toc‐amines also can serve as antioxidants.