Nitrones: not only extraordinary spin traps, but also good nitric oxide sources in vivo.

Free radicals are involved in the development of reperfusion injuries. Using a spin trap, the intensity of such lesions can be reduced. Nitrones (effective in vivo spin traps) were tried in this work as in vivo nitric oxide donors. Nitrite and nitrate concentration values (rabbit blood) were used as biomarkers of nitric oxide production. Most nitrones did not increase plasma concentrations of nitrite and nitrate; on the contrary, reduced plasma concentrations of these indicators were noted. However, glyoxal isopropyldinitrone, in a dose of 50 mg kg-1, was highly effective in increasing nitric oxide production. At the same time, nitrones do not react with hepatic homogenates, proving that the release of nitric oxide takes place in the tissues and is not related to hepatic metabolism. Before using nitrones in vivo, they were tested in vitro for the ability to release nitric oxide following a reaction with the hydroxyl radical.

Nitrones are able to release nitric oxide in aqueous environment under hydroxyl free radical attack.

Importance of a nitric oxide donor that can act as a spin trap might bring some new therapeutic possibilities regarding the treatment of ischemic diseases by reducing the intensity of free radical produced reperfusion lesions. These substances might be also used as a new type of photo protectors since they can absorb UV radiation, capture free radicals formed by interaction of UV radiation with tissue constituents, and tanning of the skin will be permitted due to nitric oxide release. The purpose of this work was to measure the ability of nitrones to release nitric oxide and how different factors (temperature, nitrone concentration, and free radicals) influence the releasing ability. Mostly, indirect determination of nitric oxide was carried out, by measuring nitrite and nitrate amounts (as decomposition products of nitric oxide), all nitrones proved to release significant amounts of nitric oxide. Nitrite measurements were made based on an HPLC-VIS method that uses pre-column derivatization of nitrite by forming an azo dye (limit of quantification: 5ng/ml). No good correlation was found between the amount of nitric oxide and temperature for most studied nitrones but between the formation of nitric oxide and nitrone concentration an asymptotic correlation was found. Fenton reagent also yielded formation of nitric oxide from nitrones and formed amounts were not different from those recorded for UV irradiation. Most of the nitrones effectively released about 0.5% of the maximum amount of nitric oxide that is chemically possible and estimated concentrations of 0.1µM were present in the solutions during decomposition.

Structural studies on the chiral selector capacity of cyclodextrin derivatives.

Chromatographic separation of enantiomers to assure or enhance chiral purity is of considerable importance and can be achieved by the use of selectors of great structural variety. Cyclodextrins are an important and frequently used class, and they are multimodal selectors since multiple chiral interactions are possible by very different mechanisms. Here, the results of a preliminary examination on the possible value of computational molecular modeling approaches for the predictability of cyclodextrin selector effects for compounds that possess both geometrical and optical isomerism are presented. Interactions between various cyclodextrins and pyrethroic acids are modeled, interpreted, and compared to experimental capillary electrophoresis data.

The quantitative characterization of free radical sources and traps by electromigration applications.

Nowadays, very diverse human activities generate urgent demands for fast, sensitive reliable innovative tools capable of detecting major industrial, military, and other dangerous products. An important part of these compounds are free radicals. Capillary electrophoresis (CE), especially in its miniaturized format (lab-on-a-chip), and other electromigration methods offer special possibilities to resolve this problem. These measurements have a great opportuness because of very wide chemical and biological role of free radicals. Several compounds, e.g. monomers and some biologically important groups (as are nitrones) oppose oxidative challenges by virtue of their trap very rapidly oxygen- or carbon-centered radicals and generating other radical species which are stable and biochemically less harmful than the original ones. In many cases, conventionally, the relative trap capacity is measured against tert.-butylhydroperoxide (TBH). In this lecture are presented numerous important free radical species (active oxygen-, nitrogen- and carbon-centered ones, as HO, NO etc) and their adequate in vitro and in vivo applied bioanalytical methods, including liquid chromatography with electrochemical detection and mass spectrometry, gas chromatography with mass spectrometry, capillary electrophoresis, electron spin resonance and chemiluminescence analysis. A simple and highly sensitive method is the capillary zone electrophoresis with amperometric detection (CZE-AD); It was introduced to determine indirectly OH by analysing its reaction products with salicylic and dihydroxybenzoic acids. Hydroxylated radical products of these acids are often used as a relative measurement in free radical research. Accurate determination of pK(a) values is important for proper characterization of newly synthesized molecules. CZE method was used for determination of their values. Are initiated new research fields as Fenton-, electro-Fenton and photoelectro-Fenton chemistry and foreseen their perspectives. Nitric oxide is an important cell signaling molecule in physiology and pathophysiology. An indirect method for monitoring nitric oxide (NO) by determining nitrate and nitrite by microchip capillary electrophoresis (CE) with electrochemical (EC) detection has been developed. The amount of nitrite formed in this reaction (analyzed by capillary electrophoresis) was compared with the amount of oxygen consumed (measured by polarography). Were observed a linear relationship between the amount of consumed oxygen and the amount of nitrite formed in the measured range. These results demonstrate that polarographic measurements of the amount of oxygen consumed in the reaction with NO could be used to estimate the concentration of dissolved NO in authentic media. Polarography is an adequate method also to quantitative kinetic study of the free radical activity and of the trapping capacity of different compounds. This method is based on measure of the catalytic polarografic current of Fe(III) in the presence of free radical sources (TBH, hydrogen-peroxydes), and their traps. Personal contribution of the authors in this field is discussed.