title: The hydrolytic autoxidation of 1,4-naphthoquinone-2-potassium sulphonate: implications for 1,4-naphthoquinone-2-potassium sulphonate-induced oxidative stress in the red blood cell.
abstract: 1,4-Naphthoquinone-2-potassium sulphonate (NQKS) undergoes an autoxidation reaction in aqueous solution under physiological conditions to produce 3-hydroxy-1,4-naphthoquinone-2-potassium sulphonate (NQKS-OH). Intermediates of dioxygen reduction, superoxide radicals, hydrogen peroxide and hydroxyl radicals, are also detected. The kinetics of the autoxidation of NQKS show a first order dependence on NQKS and hydroxide ion concentration and a zeroth order dependence on oxygen concentration. For the rate equation r = -d[O2]/dt = kappa obs., [NQKS] [-OH], kappa obs. = (6.4 +/- 0.6) X 10(2) M-1s-1 at 37 degrees C. Hydroxide ion attack on NQKS appears to be the rate determining step. The reaction may be conveniently described as a 'hydrolytic autoxidation'. The hydrolytic autoxidation of NQKS occurs in NQKS-treated red blood cells; the hydroxylated quinone NQKS-OH is produced and hydroxyl radical formation is stimulated. The importance of this reaction in NQKS-induced oxidative stress in red blood cells is discussed. The hydrolytic autoxidation of quinones bearing one or more unsubstituted (hydrogen) positions on the quinone centre is a novel mechanism by which such quinones may induce oxidative stress in cellular systems.
mesh_terms: D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005609:Free Radicals; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008706:Methemoglobin; D009285:Naphthoquinones / Q000097:blood / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010100:Oxygen; D010108:Oxyhemoglobins; D011809:Quinones / Q000097:blood; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013113:Spin Labels
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; D009285:Naphthoquinones; D010108:Oxyhemoglobins; D011809:Quinones; D012996:Solutions; D013113:Spin Labels; C019020:1,4-naphthoquinone-2-sulfonate; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D008706:Methemoglobin; D010100:Oxygen