Tetrahydroquinolines as inhibitors of radical chain oxidation of organic compounds: kinetics and mechanism of action

The effectiveness and mechanism of the antioxidant action of a number of biologically active polysubstituted tetrahydroquinolines in a model reaction of liquid-phase oxidation of 1,4-dioxane have been studied. The research into the properties of these substances in the field of pharmacology is becoming increasingly important due to their ability to act as inhibitors of radical chain oxidation of organic compounds. The fact is that the manifestation of the antioxidant properties of biologically active compounds leads to an increase in the therapeutic effect of potential drugs. In this case, the drug, simultaneously with the function of treating the target disease, additionally slows down the rate of the undesirable process of lipid peroxidation of cell membranes. The oxidation reaction has been observed at 348 K using a manometric technique, measuring the change in the concentration of absorbed oxygen in the gas phase under different initial conditions of the studied antioxidants over time. In the presence of tetrahydroquinoline (THQ) additives, the kinetic curves of oxygen absorption exhibit an induction period (τ) when the rate of oxygen absorption is immeasurably low. The dependence of τ and the rate of inhibited oxidation on the concentration of THQ has been studied and the reaction mechanism formulated, including the stage of regeneration of the inhibitor at the stage of chain termination. Using the method of mathematical modeling, the adequacy of the mechanism to the obtained experimental data has been substantiated, the rate constants of the key stages and parameters of the efficiency of inhibitor f regeneration have been found. When comparing the results of this article with previously published data, it has been found that the mechanism and antioxidant efficiency of tetrahydroquinolines depend on their structure and the nature of the active site of inhibition.