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

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 logk _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. Thek _Q values were found to be 1.30–2.57 times as large ask _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.