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Relevant academic research and scientific papers

Esters of 5-carboxyl-5-methyl-1-pyrroline N-oxide: A family of spin traps for superoxide

Apparent rate constants, at acidic pH and neutral pH for the reaction of a family of ester-containing 5-carboxyl-5-methyl-1-pyrroline N-oxides with superoxide (O2.-) were estimated, using ferricytochrome c as a competitive inhibitor. It was of interest to note that the rate constants were similar among the different nitrones and not that significantly different from that found for 5-(diethoxyphosphoryl)-5-dimethyl-1-pyrroline N-oxide. At acidic pH, the rate constant for spin trapping O2.- 3-fold greater than that at physiological pH. Subsequent experiments determined the half-life of aminoxyls, derived from the reaction of these nitrones with O2.-. The EPR spectra were modeled by using a global analysis method. The results clearly demonstrated that EPR spectra of all the aminoxyls were inconsistent with a model that included a single γ-hydrogen splitting. A better interpretation modeled them as two diastereomers with identical nitrogen splittings and slightly different β-hydrogen splittings. Detailed line width analyses slightly favored an equal line width-unequal population ratio for the two diastereomers.

Inclusion complexes of EMPO derivatives with 2,6-di-O-methyl-β- cyclodextrin: Synthesis, NMR and EPR investigations for enhanced superoxide detection

The free radical trapping properties of eight 5-alkoxycarbonyl-5-methyl-1- pyrroline N-oxide (EMPO) type nitrones and those of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) were evaluated for trapping of superoxide anion radicals in the presence of 2,6-di-O-methyl-β-cyclodextrin (DM-β-CD). 1H-NMR titrations were performed to determine both stoichiometries and binding constants for the diamagnetic nitrone-DM-β-CD equilibria. EPR titrations were then performed and analyzed using a two-dimensional EPR simulation program affording 1: 1 and 1: 2 stoichiometries for the nitroxide spin adducts with DM-β-CD and the associated binding constants after spin trapping. The nitroxide spin adducts associate more strongly with DM-β-CD than the nitrones. The ability of the nitrones to trap superoxide, the enhancement of the EPR signal intensity and the supramolecular protection by DM-β-CD against sodium l-ascorbate reduction were evaluated. The Royal Society of Chemistry 2006.

Spin trapping of Superoxide by diester-nitrones

The nitrone N[(1-oxidopyridin-1-ium-4-yl)-methylidene]-1,1- bis(ethoxycarbonyl)ethylamine N-oxide (DEEPyON) was synthesized and used as a spin trapping agent. The kinetic aspects of the Superoxide detection by this new spin trap and by two other diester-nitrones, i.e. 2,2-diethoxycarbonyl-3,4- dihydro-2H-pyrrole-1-oxide (DEPO) and N-benzylidene-1,1- bisCethoxycarbonyOethylamine N-oxide (DEEPN), were examined by determining the rate constants for the trapping reaction and for the spin adduct decay at pH 7.2. Comparing the results obtained to those given by analogous monoester-nitrones showed that both the spin trapping and the adduct decay reactions were faster in the presence of a second ester group in the cyclic nitrone series, while the Superoxide trapping capacities of linear diester-nitrones were found to be dramatically weak. It follows from this study that DEPO and 2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide (EMPO) are superior when it comes to Superoxide detection. Below 0.005 mol dm -3, DEPO is to date the only nitrone capable of clearly detecting Superoxide, while EMPO should be preferred at higher spin trap concentration. The Royal Society of Chemistry 2005.