Mass spectrometric identification of N-phenyllinoleamide metabolites in mouse peritoneal macrophages.

N-Phenyllinoleamide (NPLA), the anilide of linoleic acid, has been regarded as a marker of the case oils associated with toxic oil syndrome, but the mechanisms of toxic injury remain enigmatic. Experimental data have related an increased systemic toxic effect of heated linoleic anilides to chemical structural modifications that might also be possible by in vivo metabolism; however, little is known about their metabolism. Taking into account that NPLA is a derivative of linoleic acid, a fatty acid that can be metabolized by lipoxygenase activity to a vast array of derivatives possessing biological activity, the objective has been to elucidate the oxidative metabolism of NPLA by mouse peritoneal macrophages, a cellular model with high lipoxygenase activity. Cells were incubated with 0.1 mM NPLA spiked with N-phenyl[1-14C]linoleamide. The metabolites were separated by high-performance liquid chromatography and individually collected prior to GC/MS analysis. Identification of trihydroxy-, monohydroxy- and epoxy-derivatives of NPLA, suggests that this xenobiotic can be metabolized via the same oxidative processes as for linoleic acid. Furthermore, identification of the non-amidated monohydroxylated and trihydroxylated derivatives of linoleic acid arising from NPLA suggests an amidase-like activity with release of aniline and the free fatty acid. These results provide information about possible biological structures arising from NPLA, and open the way to evaluate the biological significance of these metabolites in the inflammatory reactions associated with toxic oil syndrome.