Analysis of Novel Hydroperoxides and Other Metabolites of Oleic, Linoleic, and Linolenic Acids by Liquid Chromatography-Mass Spectrometry With Ion Trap MSn

Lipids. 1998 Sep;33(9):843-52. doi: 10.1007/s11745-998-0280-0.

Abstract

Linoleate is oxygenated by manganese-lipoxygenase (Mn-LO) to 11S-hydroperoxylinoleic acid and 13R-hydroperoxyoctadeca-9Z,11E-dienoic acid, whereas linoleate diol synthase (LDS) converts linoleate sequentially to 8R-hydroperoxylinoleate, through an 8-dioxygenase by insertion of molecular oxygen, and to 7S,8S-dihydroxylinoleate, through a hydroperoxide isomerase by intramolecular oxygen transfer. We have used liquid chromatography-mass spectrometry (LC-MS) with an ion trap mass spectrometer to study the MSn mass spectra of the main metabolites of oleic, linoleic, alpha-linolenic and gamma-linolenic acids, which are formed by Mn-LO and by LDS. The enzymes were purified from the culture broth (Mn-LO) and mycelium (LDS) of the fungus Gaeumannomyces graminis. MS3 analysis of hydroperoxides and MS2 analysis of dihydroxy- and monohydroxy metabolites yielded many fragments with information on the position of oxygenated carbons. Mn-LO oxygenated C-11 and C-13 of 18:2n-6, 18:3n-3, and 18:3n-6 in a ratio of approximately 1:1-3 at high substrate concentrations. 8-Hydroxy-9(10)epoxystearate was identified as a novel metabolite of LDS and oleic acid by LC-MS and by gas chromatography-MS. We conclude that LC-MS with MSn is a convenient tool for detection and identification of hydroperoxy fatty acids and other metabolites of these enzymes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Liquid / methods*
  • Fatty Acids, Unsaturated / analysis*
  • Fatty Acids, Unsaturated / metabolism
  • Hydrogen Peroxide / analysis*
  • Hydrogen Peroxide / metabolism
  • Intramolecular Oxidoreductases / metabolism
  • Linoleic Acids / analysis
  • Linoleic Acids / metabolism
  • Linolenic Acids / analysis
  • Linolenic Acids / metabolism
  • Mass Spectrometry / methods*
  • Oleic Acids / analysis*
  • Oleic Acids / metabolism

Substances

  • Fatty Acids, Unsaturated
  • Linoleic Acids
  • Linolenic Acids
  • Oleic Acids
  • Hydrogen Peroxide
  • Intramolecular Oxidoreductases
  • hydroperoxide isomerase