In May 1981, a massive food-borne intoxication occurred in Spain. The so-called toxic oil syndrome (TOS) was associated with the consumption of aniline-denatured and refined rapeseed oil that was illegally sold as edible olive oil. Fatty acid anilides and fatty acid derivatives of 3-(phenylamino)propane-1,2-diol were detected in oils and implicated as potential toxic agents and markers of toxic oil batches. Epidemiological evidence points to 3-(phenylamino)propane-1,2-diol derivatives as the putative toxic agents, which were generated during the refining process at the ITH refinery. Here we present the biotransformation and clearance of 3-(phenylamino)propane-1,2-diol (PAP) administered intraperitoneally to A/J and C57BL/6 mice that have been proposed as a murine model for the immunological features of TOS. Mice eliminated 6 microCi of [U-(14)C]PAP during a 24 h period, mostly in urine. Animals exhibited urine elimination rates of 70 and 36% in A/J and C57BL/6 strains, respectively. A/J mice exhibited no increase in the elimination rate when induced with beta-naphthoflavone, whereas C57BL/6 did increase the rate of elimination to 57%. Feces contributed to a lesser extent to the elimination rate (0.6 and 3.3% in A/J and C57BL/6 mice, respectively). Radioactivity remaining in organ tissues was lower than 1% (liver, lung, kidney, spleen, heart, and muscle). Metabolic species in urine were identified by HPLC coupled to UV and radioisotope detectors and further GC/MS analyses. 2-Hydroxy-3-(phenylamino)propanoic acid metabolite was the major chemical species excreted in urine in both strains, in both control and induced animal groups. This compound was the main urinary metabolite of PAP, and unmetabolized PAP excreted in urine constituted less than 1% of the total administered dose. Two additional highly polar metabolites also detected in urine were identified as 3-[(4'-hydroxyphenyl)amino]propane-1,2-diol and 2-hydroxy-3-[(4'-hydroxyphenyl)amino]propanoic acid. These findings are the first reported on PAP metabolism and clearance in mice strains and suggest that PAP can be extensively metabolized in vivo and potential reactive species can be generated.

Epidemiological studies have pointed to fatty acid mono- and diesters of 3-(N-phenylamino)propane-1,2-diol (PAP) as the biomarkers of the toxic oil batches that caused toxic oil syndrome (TOS), an intoxication episode that occurred in Spain in 1981, causing over 400 deaths and affecting more than 20000 people. The biotransformation of PAP administered intraperitoneally to two mouse strains produced potentially toxic metabolites. The identification of 3-(4'-hydroxyphenylamino)propane-1,2-diol among those metabolites was important because the compound can generate the quinoneimine intermediate 2. The potential toxicity of quinoneimines has been attributed primarily to their electrophilic character. Accordingly, the reactions of 2 with N-acetylcysteine, N-acetylcysteine methyl ester, and GSH were investigated. Quinoneimine 2 reacts with the N-acetylcysteine methyl ester to give the expected conjugate as a major product, accompanied by the corresponding bis and tris adducts. The monoadduct, when isolated in pure form, undergoes spontaneous oxidation to generate a new quinoneimine intermediate, which in turn rearranges and undergoes hydrolysis to afford the thiol adduct formally derived from the quinoneimine generated from p-aminophenol. The same overall pathway was observed for the reaction of 2 with N-acetylcysteine and GSH. Both thiol reagents reacted with the quinoneimine to give the corresponding adducts in which the addition took place at the ortho position with respect to the amino group. These conjugates were also unstable and ultimately afforded the corresponding adduct derived from p-aminophenol. The relevancy of these results to TOS, as well as their potential generalization for quinoneimines derived from other xenobiotics, is discussed herein.