76673-35-3Relevant articles and documents
Chemical Sources of Singlet Oxygen. 3. Peroxidation of Water-Soluble Singlet Oxygen Carriers with the Hydrogen Peroxide-Molybdate System
Aubry, J. M.,Cazin, B.,Duprat, F.
, p. 726 - 728 (1989)
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Kinetic study of the quenching reaction of singlet oxygen by flavonoids in ethanol solution
Nagai, Souichi,Ohara, Keishi,Mukai, Kazuo
, p. 4234 - 4240 (2005)
The quenching rate of singlet oxygen (1O2) by seven kinds of flavonoids (flavone, flavonol, chrysin, apigenin, rutin, quercetin, and myricetin) with 2,3-double bonds has been measured spectrophotometrically in ethanol at 35°C. The overall rate constants kQ (=kq + kt, physical quenching + chemical reaction) increased as the number of OH groups substituted to the flavone skeleton (that is, the total electron-donating capacity of flavonoids) increases. The existence of catechol or pyrogallol structure in the B-ring is essential for the 1O 2 quenching of flavonoids. Log kQ was found to correlate with their peak oxidation potentials, EP; the flavonoids that have smaller EP values show higher reactivities. Similarly, log k Q values of flavonoids correlate with the energy level of the highest occupied molecular orbital (EHOMO), calculated by the PM3 MO method, and the longest wavelength ππ* excitation energy (Eex). The contribution of the chemical reaction (kr) was found to be negligible in these flavonoids. The kQ values of rutin, quercetin, and myricetin [(1.21-5.12) × 108 M-1 s-1] were found to be larger than those of lipids [(0.9-6.4) × 104 M-1 s-1], amino acids (7 M-1 s-1), and DNA (5.1 × 105 M -1s-1). The result suggests that these flavonoids may contribute to the protection of oxidative damage in foods and plants, by quenching 1O2.
Formation of Superoxide Ion via One-Electron Transfer from Electron Donors to Singlet Oxygen
Saito, Isao,Matsuura, Teruo,Inoue, Kenzo
, p. 3200 - 3206 (2007/10/02)
The formation of superoxide ion (O2-.) via one-electron transfer from substituted N,N-dimethylanilines to singlet oxygen (1O2) was examined in phosphate buffer by employing a water-soluble oxygen source and a combination of p-nitrotetrazolium blue (NBT) and superoxide dismutase (SOD) as a detecting reagent for O2-..When a solution of an electron-donor-substituted N,N-dimethylaniline, NBT, and 3-(1,4-epidioxy-4-methyl-1,4-dihydro-1-naphthyl)propionic acid in phosphate buffer at pH 7.5 was incubated at 35 deg C, NBT was reduced to formazan.The inhibition of the reduction of NBT to formazan by SOD indicated the formation of O2-..Control experiments demonstrated that O2-. is produced by a direct reaction between 1O2 and the amine.Both the yield of O2-. and the quenching rate constants of 1O2 are well correlated with the oxidation potentials of these amines.Tetramethyl-p-phenylenediamine having a quenching rate constant close to a diffusion-controlled limit is the most effective for the generation of O2-. A plot of the log of the quenching rate constant of 1O2 by the amines against the calculated free-energy change (ΔG) for full electron transfer showed a linear relationship with a slope of -0.19 +/- 0.05 mol/kcal.The correlation of the log of the relative yield of O2-. against ΔG strongly supports the electron-transfer mechanism for the formation of O2-..It was demonstrated that an electron-transfer reaction giving rise to O2-. is only possible for aromatic amines with oxidation potentials less than ca. 0.5 V vs.SCE in aqueous media.
