Effect of Monosaccharide Additives on the Kinetics and Mechanism of Antiradical Action of Natural Carboxyl-Containing Phenols in Aquatic Environments

Using the activated chemiluminescence method, it was found that in the presence of monosaccharide additives, the antiradical activity of phenolic carboxylic and hydroxycinnamic acids in the reaction with 2-amidinoisopropane-2-peroxyls in an aqueous medium at pH 2 increases significantly. The found synergistic effect is most pronounced (over 90%) at a phenolic acid : monosaccharide ratio in solution of 7 : 3 (with a total mixture concentration of 8 × 10–5 mol/L) for binary mixtures of sinapic, gentisic, and ferulic acids with galactose, mannose and glucose. The mechanism of the synergistic action of the compositions in the reaction with peroxyl radicals consists in the formation of an intermolecular hydrogen-bonded complex of the acid with the reduced and oxidized forms of the monosaccharide. The transition states and activation parameters of the synergistic reactions were calculated using the DFT method. It has been established that participation in the reaction with peroxy radicals of ferulic acid in the composition of complexes with galactose and the corresponding galactonic acid contributes to a decrease in the enthalpy of activation of the reaction by 14–21 kJ/mol (compared to the reaction without the addition of monosaccharide) and the manifestation of experimentally established synergistic effects.