61540-96-3Relevant academic research and scientific papers
The chain-breaking antioxidant activity of phenolic compounds with different numbers of O-H groups as determined during the oxidation of styrene
Tikhonov, Ivan,Roginsky, Vitaly,Pliss, Evgeny
, p. 92 - 100 (2009)
The technique based on monitoring oxygen, consumption was applied to test 18 polyphenols (PP) and model phenolics as a chain-breaking antioxidant during the oxidation of styrene initiated by 2,2′-azobis(2,4- dimethylvaleronitril) at 37°C. The chain-breaking capability of PP was characterized by two parameters: the rate constant k1 for the reaction of antioxidants with the peroxy radical produced from styrene and the stoichiometric coefficient of inhibition, f, which shows how many kinetic chains are terminated by one molecule of PP. Rate constants k1 × 105 (in M-1 s-1) were found to be 10 (catechol), 27 (pyrogallol), 34 (3,6-di-tert-Bucatechol), 4.3 (protocatechic acid), 12 (gallic acid), 15 (caffeic acid), 1 increases when going from one to two and three adjacent O-H groups in a benzene ring (catechol and pyrogallol derivatives, respectively). At the same time, two O-H. groups in metaposition in a A-ring of flavonoids actually do not participate in the inhibition. For the majority of PP, f is near to 2 independent of the number of OH groups. The correlation of k1 with the structure of PP and the O-H bond dissociation enthalpy has been discussed.
A kinetic study of the reactions of sulfate and dihydrogen phosphate radicals with epicatechin, epicatechingallate, and epigalocatechingallate
Villata, Laura S.,Gonzalez, Monica C.,Martire, Daniel O.
, p. 391 - 396 (2010)
The bimolecular rate constants for the reactions of sulfate radicals with epicatechin (EC), epicatechingallate (ECG), and epigallocatechingallate (EGCG) were found to be (1.46 ± 0.06) × 109, (1.20 ± 0.08) × 109, and (1.04 ± 0.07) × 109, respectively. The activation energy [EA = 9 ± 3 kJ mol -1] and preexponential factor [A = (4.8 ± 0.6) × 10 10] for the reaction of EC with the sulfate radical were measured in the temperature range 288-303 K. The phenoxyl radicals of EC (λmax = 310 nm) were obtained both by the reaction of this flavonoid with the sulfate radicals and by photoionization. The measured bimolecular rate constants for the reactions of the dihydrogen phosphate radicals with EC, ECG, and EGCG were (7.8 ± 0.9) × 108, (8.5 ± 0.4) × 108, and (6.8 ± 0.4) × 108, respectively.
