Linoleic acid oxidation in the presence of amino compounds produces pyrroles by carbonyl amine reactions.

The reactions of 13-hydroperoxy-9(Z),11(E)-octadecadienoic acid (13-LOOH) and its degradation product 4,5(E)-epoxy-2(E)-decenal with butylamine and lysine were studied to determine whether pyrrole derivatives isolated in model reactions were produced in complex systems involving hydroperoxides. Incubated reaction mixtures were studied by gas chromatography coupled with mass spectrometry or high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS), and some compounds were isolated by column chromatography or semipreparative HPLC, and identified by 1H- and 13C-nuclear magnetic resonance spectroscopy and MS. The reaction of epoxyalkenals with amino groups produced two types of pyrrole derivatives: 1-substituted 2-(1'-hydroxyalkyl)pyrroles and 1-substituted pyrroles. 1-Substituted 2-(1'-hydroxyalkyl)pyrroles were responsible for the development of color and fluorescence by a polymerization reaction, which implied the formation of dipyrrylmethanes and dipyrrylmethenes. 1-Substituted pyrroles were final products in these reactions and their determination might be used as an index of oxidative stress. The above reactions were also observed between 13-LOOH and amino compounds, and suggested that the pyrrole polymerization mechanism plays a role in the fluorescence observed by reaction of hydroperoxides and amino groups.