Kinetic study of quenching reactions of singlet oxygen and scavenging reactions of free radicals by alpha-, beta-, gamma- and delta- tocopheramines in ethanol solution and micellar dispersion.
Quenching reactions of singlet oxygen and scavenging reactions of free radicals by alpha-, beta-, gamma- and delta-tocopheramines (Toc-amines) were investigated spectrophotometrically in ethanol and Triton X-100 micellar dispersions. The rate constants of quenching of singlet oxygen (kQ) by alpha-, beta-, gamma- and delta-Toc-amines increased as the total electron donating capacity of the methyl groups at the aromatic ring increased. A plot of logkQ vs. peak oxidation potential (Ep) 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 kQ values were found to be 1.30-2.57 times as large as kQ for alpha-tocopherol (alpha-Toc). Although alpha-Toc has the highest antioxidant activity among natural tocopherols and related phenols, Toc-amines also can serve as antioxidants.
Itoh
S
S
Department of Chemistry, Faculty of Science, Ehime University, Matsuyama, Japan.
Nagaoka
S
S
Mukai
K
K
Ikesu
S
S
Kaneko
Y
Y
D000975:Antioxidants; D000431:Ethanol / Q000737:chemistry; D016166:Free Radical Scavengers; D007700:Kinetics; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D026082:Singlet Oxygen; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism
D000975:Antioxidants; D016166:Free Radical Scavengers; C092254:gamma-tocopheramine; D014810:Vitamin E; D026082:Singlet Oxygen; C092255:delta-tocopheramine; D000431:Ethanol; D011092:Polyethylene Glycols; C092253:beta-tocopheramine; C092252:alpha-tocopheramine; D010100:Oxygen