2-2--azino-di-(3-ethylbenzothiazoline)-6-sulfonic-acid and 1-4-dihydropyridine

A series of eight commercial C-4 substituted 1,4-dihydropyridines and other synthesized related compounds were tested for direct potential scavenger effect towards alkylperoxyl radicals and ABTS radical cation in aqueous Britton-Robinson buffer pH7.4. A direct quenching radical species was established. The tested 1,4-dihydropyridines were 8.3-fold more reactive towards alkylperoxyl radicals than ABTS cation radical, expressed by their corresponding kinetic rate constants. Furthermore, NPD a photolyte of nifedipine and the C-4 unsubstituted 1,4-DHP were the most reactive derivatives towards alkylperoxyl radicals. The pyridine derivative was confirmed by GC/MS technique as the final product of reaction. In consequence, the reduction of alkylperoxyl and ABTS radicals by 1,4-dihydropyridines involved an electron transfer process. Also, the participation of the hydrogen of the 1-position appears as relevant on the reactivity. Results of reactivity were compared with Trolox.

Topics: Benzothiazoles; Cations; Dihydropyridines; Free Radicals; Mass Spectrometry; Peroxides; Spectrophotometry, Ultraviolet; Sulfonic Acids

In the present paper, a direct quenching of radical species by a number of synthesized nitrosoaryl 1,4-dihydropyridines and their parent nitroaryl 1,4-dihydropyridines was determined in aqueous media at pH 7.4. These two series of compounds were compared with the C-4 unsubstituted 1,4-dihydropyridines derivatives and the corresponding C-4 aryl substituted 1,4-dihydropyridines derivatives. Kinetic rate constants were assessed by UV-Vis spectroscopy. Nitrosoaryl derivatives were more reactive than the parent nitroaryl 1,4-dihydropyridines. Our results strongly support the assumption that the reactivity between the synthesized 1,4-dihydropyridines derivatives with alkylperoxyl radicals involves electron transfer reactions, which is documented by the presence of pyridine as final product of reaction and the complete oxidation of the nitroso group to give rise the nitro group in the case of the nitrosoaryl 1,4-dihydropyridines derivatives.

Topics: Benzothiazoles; Cations; Chromatography, High Pressure Liquid; Dihydropyridines; Free Radicals; Gas Chromatography-Mass Spectrometry; Molecular Structure; Nitro Compounds; Peroxides; Sulfonic Acids

A series of C4-substituted 1,4-dihydropyridines (DHP) with either secondary or tertiary nitrogen in the dihydropyridine ring were synthesized. All of these compounds together with some commercial DHP derivatives were tested for potential scavenger effects toward alkyl, alkylperoxyl radicals, and ABTS radical cation in aqueous media at pH 7.4. Kinetic rate constants were assessed either by UV/vis spectroscopy or GC/MS techniques. Tested compounds reacted faster toward alkylperoxyl radicals and ABTS radical cation than alkyl ones. N-Ethyl-substituted DHPs showed the lowest reactivity. Kinetic results were compared with either trolox or nisoldipine. Using deuterium kinetic isotope effect studies, we have proved that the hydrogen of the 1-position of the DHP ring is involved in the proposed mechanism. This fact is mostly noticeable in the case of alkyl radicals. In all cases, the respective pyridine derivative was detected as the main product of the reaction.

Topics: Benzothiazoles; Cations; Chromans; Dihydropyridines; Free Radical Scavengers; Free Radicals; Gas Chromatography-Mass Spectrometry; Hydrogen-Ion Concentration; Kinetics; Nisoldipine; Peroxides; Spectrophotometry, Ultraviolet; Sulfonic Acids; Vitamin E