5.5- Dimethyl-pyrroline-N-oxide

The use of nitrone scavengers was precedented by the work of Iwamura and Inamoto (1967), who had used esr spectroscopy to detect the nitroxide formed by addition of cyanopropyl radicals to the cyclic nitrone, 5,5-dimethyl-pyrroline-N-oxide (DMPO) [2], and had actually isolated the cyanopropyl radical adduct of the nitrone [3]. 

Uric acid is present in human plasma at much higher levels than those encountered in other primates because the enzyme urate oxidase is absent from human tissues (Cutler 1984). it has therefor e been proposed that uric acid is an important antioxidant for humans (Ames et al. 1981). Urate reacts with peroxynitrite with an apparent second order rate constant of 4.8 x 10 M s in a complex process, which is accompanied by oxygen consumption and formation of allantoin, alloxan, and urate derived radicals (Santos et al. 1999). The main radical was identified as the aminocarbonyl radical by the electrospray mass spectra of its 5,5-dimethyl-/-pyrroline-N-oxide adduct. Mechanistic studies suggested that urate reacts with peroxynitrous acid and with the radicals generated from its decomposition to form products that can further react with peroxynitrite anion. 

Kamibayashi M, Oowada S, Kameda H et al (2006) Synthesis and characterization of a practically better DEPMPO-type spin trap, 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-l-pyrroline N-oxide (CYPMPO). Free Radio Res 40 1166-1172... 

In related work, the reactions of hydrogen peroxide with iron(II) complexes, including Feu(edta), were examined.3 Some experiments were carried out with added 5.5"-dimethyl-1-pyrroline-N-oxide (DMPO) as a trapping reagent fa so-called spin trap) for HO. These experiments were done to learn whether HO was truly as free as it is when generated photochemically. The hydroxyl radical adduct was indeed detected. but for some (not all) iron complexes evidence was obtained for an additional oxidizing intermediate, presumably an oxo-iron complex. 

Recendy, PEN, a-4-pyridyl-oxide-N-t-butyl nitrone (POEN) or 5-5,dimethyl-1, pyrroline-N-oxide (DMPO) were evaluated in models of experimental shock (endo-toxic, traumatic and mesenteric artery occlusion in rats). All three nitrones, when given prior to the insult intraperitoneally, were protective. When the nitrone s spin trapping ability was inactivated by exposure to solar light and air, they were no longer efficacious (Novelli, 1992). 

Duchenne muscular dystrophy dimethyl formamide 5,5-dimethyl-1 -pyrroline-1 -oxide deoxynucleic acid diphenylene iodonium endothelium-derived relaxing factor epidermal growth factor early growth phase response gene ethyleneglycol- bis- (p- aminoethyl)-N,N,N, N -tetraacetic acid... 

As a means of identifying the potent oxidant another approach was made. By the use of certain organic compounds one can infer the presence of a free radical by converting a highly unstable one such as OH to a much more stable compound which can accumulate in solution, rendering its detection by electron spin resonance possible. To measure the presence of OH the compound DMPO (5,5-dimethyl l-pyrroline-N-oxide) has been used The characteristic adduct of OH with... 

Oxidation of 2,4,4-trimethyl - A1 -py rroline V-oxide with selenium dioxide, followed by treatment with hydrogen chloride, causes ringopening and reclosure to 2,3,4,5-tetrahydro-3,3-dimethyl-5-oxo-pyridine N-oxide (111). Clemmensen reduction of 111 forms 2,4,4-trimethyl-d 1-pyrroline (112) by ring-contraction.334... 

The reaction of 5,5-dimethyl-l-pyrroline 1-oxide with dimethylketene N-phenylimine leading to pyrrolo[l,2-a]imidazol-2(3H)-ones (190) proceeds via initial formation of zwitterion (188). Subsequent sigmatropic rearrangement of (188) gives zwitterion (189), capable of undergoing ring closure to (190) (79JOC4543). 

ESR (Electron Spin Resonance) spectrum (Fig. 1.2) recorded during electrolysis of DMPO (5.5 dimethyl-1-pyrroline-N-oxide) solution on BDD confirms the formation of OH during anodic polarization of diamond electrodes. It has been reported that the BDD-hydroxyl radical interaction is so weak (no free p or d orbitals on BDD) that the OH can even be considered as quasi-free. These quasi-ffee hydroxyl... 

The EPR spin-trapping techniques were used to obtain evidence for the formation of a radical intermediate in the biomimetic Fe(n)-induced degradation of arteflene 194 in the presence of sodium 3,5-dibromo-4-nitrosobenzene-sulfonate (DBNBS) and 5,5-dimethyl-l-pyrroline /V-oxide (DMPO) <2000JOC1578>. 

The existence of free hydroxyl radicals in photo-initiated AOPs can be proven by applying a well-established method, the so-called spin trapping technique. The diamagnetic spin trap 5,5 -dimethyl-1-pyrroline N-oxide (DMPO) forms a stable paramagnetic spin-adduct with OH radicals. Its formation can be detected by electron paramagnetic resonance (EPR) spectroscopy. The underlying chemistry of... 

C6H11CI 4-chloro-2-hexene 6734-98-1 396.15 34.967 1,2 8112 C6H11NO 5,5-dimethyl-1-pyrroline N-oxide 3317-61-1 474.25 41.416 2... 

A new spin-trap, 5-(diethoxyphosphorylmethyl)-5-methyl-4,5-dihydro-3H-pyrrole N-oxide (48), " and its hydroxyl- and superoxide-spin adducts, have been compared with the analogues obtained with 5-(diethoxyphosphoryl)-5-methyl-4,5-dihydro-3H-pyrrole N-oxide (49 DEPMPO) and with 5,5-dimethyl-1-pyrroline N-oxide (50 DMPO), and overall the spin trapping behaviour of 48 was found to be more similar to that of DMPO than DEPMPO. 

CuZnSOD has been demonstrated to act as a peroxidase, oxidizing various substrates, among them nitrite (to NO2) [57] and relatively bulky molecules such as 5,5-dimethyl- 1-pyrroline N-oxide (DMPO to DMPO-OH), tyrosine (to dityrosine) or 2,2 -azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS to a cation radical). However, the enzyme becomes inactivated in the presence of H2O2. Apparently, hydrogen peroxide reduces Cu- at the active site of the enzyme. Subsequent reaction of H2O2 with Cu generates a potent oxidant (Cu+-0 or Cu + CH) that can attack the adjacent histidine residue and thus inactivate the enzyme, or oxidize an alternative substrate [3]. Most authors assume that the mechanism of the peroxidative action of CuZnSOD, significantly accelerated in the presence of bicarbonate, consists in oxidation of bicarbonate to a carbonate radical anion able to oxidize other substrates [58,59] ... 

Britigan, B. E., and Hamill, D. R. (1989). The interaction of 5,5-dimethyl-l-pyrroline-N-oxide with human myeloperoxidase and its potential impact on spin trapping of neutrophil-derived free radicals. Arch. Biochem. Biophys. 275, 72-81. 

HO radicals to inflammatory processes in synovial fluids from patients with RA has been recently proven by ESR (electron spin resonance) as well as using spin traps such as 5,5-dimethyl-1-pyrroline-N-oxide to convert the highly reactive, short-lived HO radicals into a more stable, more simple detectable compound [74],... 

Spin-traps DMPO (5,5-dimethyl-l- pyrroline-N-oxide), MNP (2-methyl-2-nitroso-propane, dimer), dG (2 -deoxyguanosine monophosphate), 8-HOdG standard (8-hydroxy-2 -deoxyguanosine) and deferoxamine mesylate were purchased from Sigma phosphate buffer (pH 7.4), hydrogen peroxide (H2O2) (30%), were purchased from Merck. All other chemicals used were of analytical quality. 

Note Values were taken from A. B. Ross, NDRL/NIST Solution Kinetics Database, v. 2.0, Standard Reference Data, NIST, Gaithersburg, MD 20899, USA (http //allen.rad.nd.edu), also found in Ref. 32. DMPO stands for 5,5-dimethyl-l-pyrroline N-oxide. 

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