NMR spin trapping: Detection of free radical reactions using a phosphorus-containing nitrone spin trap

• Published in: Magnetic resonance in medicine 1999-08, Vol.42 (2), p.228-234
• Main Authors: Khramtsov, Valery, Berliner, Lawrence J., Clanton, Thomas L.
• Format: Article
• Language: English
• Subjects: 31P-NMR; 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide; Biological and medical sciences; Cyclic N-Oxides - chemistry; electron paramagnetic resonance; Electron Spin Resonance Spectroscopy; Free Radicals; Humans; Investigative techniques, diagnostic techniques (general aspects); Magnetic Resonance Spectroscopy - methods; Medical sciences; Miscellaneous. Technology; Molecular Structure; Neutrophils - metabolism; Radiodiagnosis. Nmr imagery. Nmr spectrometry; reactive oxygen; Spin Trapping
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/(SICI)1522-2594(199908)42:2<228::AID-MRM3>3.0.CO;2-T

This study employs 31P‐nuclear magnetic resonance (NMR) to probe for changes in molecular structure arising from reactions between free radicals and a phosphorus‐containing nitrone spin trap, 5‐diethoxyphosphoryl‐5‐methyl‐1‐pyrroline‐N‐oxide (DEPMPO). A number of biologically relevant free radical reactions were detected: a) reactions of DEPMPO with ⋅OH resulted in a new 31P‐NMR resonance at 27.05 ppm (shifted from the parent compound at 23.67 ppm); evidence suggests that this species is a diamagnetic hydroxy‐pyrrolidone reduction product; b) 31P‐NMR spectra of DEPMPO/⋅CH3 reactions resulted in peaks at 24.54, 30.83, and 32.31 ppm, while DEPMPO/⋅CH2OH produced peaks at 24.05, 30.80 and 32.52 ppm; in the presence of excess ascorbate, only resonances between 30 and 32 ppm were evident, which we have tentatively assigned to the hydroxylamine isomers of their respective adducts; and c) reaction of DEPMPO with O2⋅−, produced by xanthine/xanthine oxidase or stimulated neutrophils, resulted in a single line, indistinguishable from DEPMPO/⋅OH reaction products. We conclude that NMR spin trapping is a useful approach for detecting free radical reaction pathways. It may have future applications for human free radical biology and imaging. Magn Reson Med 42:228–234, 1999. © 1999 Wiley‐Liss, Inc.