Metabolism of (R)- and (S)-3-(Phenylamino)propane-1,2-diol in C57BL/6- and A/J-Strain Mice. Identification of New Metabolites with Potential Toxicological Significance to the Toxic Oil Syndrome

Abstract

The Toxic Oil Syndrome was a massive food-borne intoxication that occurred in Spain in 1981. Epidemiological studies point to 3-(phenylamino)propane-1,2-diol (PAP) derivatives as the putative toxic agents. We report further identification of metabolites cleared in urine of A/J and C57BL/6 mice in which (R)- and (S)-3-(phenylamino)propane-1,2-diol were administered intraperitoneally. This investigation is an extension of previous studies carried out with the racemic compound [Ladona, M. G., Bujons, J., Messeguer, A., Ampurdanés, C., Morató, A., and Corbella, J. (1999) Chem. Res. Toxicol. 12, 1127-1137]. Both PAP enantiomers were extensively metabolized, and several metabolites were eliminated in urine. The HPLC profiles of the urine samples of both mouse strains treated with each enantiomer were qualitatively similar, but differences were found in a relatively higher proportion of several detected metabolites in mice treated with (R)-PAP compared with those treated with (S)-PAP. The main urine metabolite continues to be 2-hydroxy-3-(phenylamino)propanoic acid (1), which confirms our previous results obtained with rac-PAP. In addition to the detection of other metabolites already reported in our previous paper, interesting evidence is provided on the presence of 4-aminophenol and paracetamol conjugates in the urine samples from both mouse strains. The detection of these metabolites suggests the in vivo formation of quinoneimine PAP derivatives. Indeed, some quinoneimine species (11 and 12), as well as other PAP metabolites (13) that bear modifications in the alkyl chain, have been tentatively identified in mouse urine. These metabolic findings might imply a potential toxicological significance for the Toxic Oil Syndrome.

In Vitro Bioactivation of 3-(N-Phenylamino)propane-1,2-diol by Human and Rat Liver Microsomes and Recombinant P450 Enzymes. Implications for Toxic Oil Syndrome

“…Consistent with previous in vivo experiments , , the incubations of PAP in the presence of RLM or HLM showed the capacity of P450s to hydroxylate PAP to yield phenol 1 . The relatively high apparent K m values (millimolar range) suggest that the enzymes involved in this oxidative enzyme reaction have a relatively low affinity for the substrate.…”

“…Furthermore, 4-aminophenol and paracetamol were found in the mice's urine after treatment with glucoronidase and sulfatase. These two compounds could be generated from quinoneimine 2 after prototropic rearrangement and further hydrolysis to yield 4-aminophenol, which after in vivo acetylation would give rise to paracetamol (Scheme 1) (13,14). These findings may have important implications for the toxicology of TOS, by providing evidence not only that PAP metabolism can generate well-known toxic products, such as 4-aminophenol and paracetamol, but also that potentially toxic intermediates, such as quinoneimine 2, could be involved in these bioactivations.…”

Synthesis and Stability Studies of the Glutathione and N-Acetylcysteine Adducts of an Iminoquinone Reactive Intermediate Generated in the Biotransformation of 3-(N-Phenylamino)propane-1,2-diol: Implications for Toxic Oil Syndrome

“…Synthesis of Quinoneimine 2. The oxidation of phenol 1 was carried out following the procedure described by Bujons et al (14). Phenol 1 (67 mg, 0.36 mmol) and Ag 2O (94 mg, 0.40 mmol) were stirred in a 1:1 methanol:acetonitrile mixture (18 mL) for 20 min at 20 °C, and the reaction was monitored by HPLC.…”

“…These experiments showed that, among other pathways that could involve oligomer formation, quinoneimine 2 rearranges to give the corresponding Schiff base, which in turn is facilely hydrolyzed in the reaction medium to give p-aminophenol. It is worth noting that p-aminophenol was also identified as a urine metabolite in the aforementioned in vivo assays (14). Thus, the presence of p-aminophenol may be considered as indirect evidence of the generation of the quinoneimine intermediate 2.…”

The Spanish toxic oil syndrome 20 years after its onset: a multidisciplinary review of scientific knowledge.

“…We know little about PAP ester absorption, distribution, and metabolism. intermediates or from hydroxylation at the aromatic ring have been identified; the detection of some of these species suggests the in vivo formation of quinoneimine PAP derivatives (55). Closa et al (56) have reported on the capacity of PAP fatty acid esters to be absorbed by the gastrointestinal tract of experimental rats and metabolized in a similar manner as phospholipids.…”