Potentiometry as a method of antioxidant activity investigation.

Problems of terminology applied for antioxidant properties of substances are being discussed. Selection of the term 'Antioxidant Activity' is being proved. New method of the determination of this index is offered, where electrode potential shift as a result of redox chemical reaction between substance to be determined and oxidized form of mediator system serves as a source of information. Good correlation is fixed between data obtained by potentiometric method and known chemiluminescent, Randox methods, and photometric method with the use of stable radical 2,2-diphenyl-1-picrylhydrasyl. Accuracy and reliability of the results, simplicity of the analysis procedure and its self-descriptiveness make the method offered to become good alternative to the known methods of antioxidant activity determination.

Superoxide dismutase: determination of activity by inhibition of photosensitized chemiluminescence of glycyltryptophan.

A technique for quantitative determination of superoxide dismutase (SOD) in biological material is described. The technique is based on the riboflavin-photosensitized oxidation of Gly-Trp, which is accompanied by chemiluminescence. Formation of the luminescent product is inhibited by SOD. The dependence of SOD activity on reciprocal intensity of chemiluminescence is linear. The concentration for 50% inhibition is 7.5 ng/ml, and the minimum reliably determined concentration is about 2 ng/ml. The reaction is not sensitive to high concentrations of cyanide, which allows the separate determination of Cu,Zn- and Mn-SOD in mixtures.

Changes in superoxide production rate and in superoxide dismutase and glutathione peroxidase activities in subcellular organelles in mouse liver under exposure to low doses of low-intensity radiation.

The functioning of the antioxidant system in mouse liver at increased stationary concentration of active oxygen species induced by whole-body chronic exposure of mice to gamma-irradiation (137Cs, 0.6 cGy/day, 9 days) was studied. Synchronous changes (growth with an extreme) in activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) are found that may be considered as evidence in favor of maintenance of regulatory links in the antioxidant system of liver. The superoxide production rate in microsomes and nuclei also changed with an extreme with the rise in accumulated radiation dose. In microsomes the superoxide production rate reached a maximum at lower doses than the activity of Cu,Zn-SOD did. In nuclei the increase in superoxide production rate was not compensated by the rise in Cu,Zn-SOD activity within the studied dose range. The findings indicate some imbalance between production and consumption of superoxide radicals in microsomes and nuclei; in mitochondria these processes are balanced, leading to more resistance to low-dose irradiation.

Photoprotector and antioxidant properties of histamine-containing peptidomimetics in the photooxidation of glycyltryptophan.

The natural imidazole-containing dipeptide carnosine in vitro exhibits several antioxidant properties; however, in vivo its activity is limited due to enzymatic hydrolysis. A family of original histamine-containing peptidomimetics, i.e., carcinine (beta-alanylhistamine), N-acetylcarcinine (N-acetyl-beta-alanylhistamine), and L-prolylhistamine, which exhibit significant resistance to dipeptidases and retain antioxidant activity, was synthesized. The effect of these compounds on chemiluminescence of glycyltryptophan (Gly-Trp) associated with its photooxidation at the wavelengths over 280 nm and oxidation photosensitized by riboflavin and Rose Bengal was studied. It is shown that all three peptidomimetics efficiently react with singlet oxygen with the rate constant 9.107 M-1.sec-1, exhibit free-radical scavenging activity in the course of riboflavin-sensitized Gly-Trp oxidation (C50% = 8-15 mM), and quench the photoexcited triplet states of the molecules. Unlike these peptidomimetics, carnosine does not react with superoxide generated during the photooxidation of Gly-Trp in the used test system. The data demonstrate photoprotector and antioxidant properties of histamine-containing peptidomimetics in the photooxidation of biological molecules.