The lactate-dependent enhancement of hydroxyl radical generation by the Fenton reaction

M. Aktar Ali, Fumihiko Yasui, Seiichi Matsugo, Tetsuya Konishi

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

The effect of lactic acid (lactate) on Fenton based hydroxyl radical (·OH) production was studied by spin trapping, ESR, and fluorescence methods using DMPO and coumarin-3-carboxylic acid (3-CCA) as the ·OH traps respectively. The ·OH adduct formation was inhibited by lactate up to 0.4 mM (lactate/iron stoichiometry = 2) in both experiments, but markedly enhanced with increasing concentrations of lactate above this critical concentration. When the H2O2 dependence was examined, the DMPO-OH signal was increased linearly with H2O2 concentration up to 1 mM and then saturated in the absence of lactate. In the presence of lactate, however, the DMPO-OH signal was increased further with higher H2O2 concentration than 1 mM, and the saturation level was also increased dependent on lactate concentration. Spectroscopic studies revealed that lactate forms a stable colored complex with Fe3+ at lactate/Fe3+ stoichiometry of 2, and the complex formation was strictly related to the DMPO-OH formation. The complex formation did not promote the H2O2 mediated Fe3+ reduction. When the Fe3+-lactate (1: 2) complex was reacted with H2O2, the initial rate of hydroxylated 3-CCA formation was linearly increased with H2O2 concentrations. All the data obtained in the present experiments suggested that the Fe3+-lactate (1:2) complex formed in the Fenton reaction system reacts directly with H2O2 to produce additional ·OH in the Fenton reaction by other mechanisms than lactate or lactate/Fe3+ mediated promotion of Fe3+/Fe2+ redox cycling.

Original languageEnglish (US)
Pages (from-to)429-438
Number of pages10
JournalFree Radical Research
Volume32
Issue number5
DOIs
StatePublished - 2000

Keywords

  • Fe-lactate complex
  • Fenton reaction
  • Generation
  • Lactic acid
  • Spin trapping ESR
  • ·OH
  • ·OH enhancement

ASJC Scopus subject areas

  • Biochemistry

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