Biochemical and Biophysical Research Communications
First evidence that cytochrome P450 may catalyze both S-oxidation and epoxidation of thiophene derivatives
Section snippets
Materials and methods
All reagents were of the highest quality commercially available. 2PT was purchased from Aldrich (L’Isle d’Abeau Chesnes, France).
Tritiation of 2PT. Tritiation at position 5 of 2PT was performed by taking advantage of the previously reported easy exchange of thiophene hydrogens at C2 and C5 under acidic conditions [3], [16]. A mixture of 20 mg 2PT, 200 μl trifluoroacetic anhydride, and 30 μl tritiated water (16 μCi/μmol) in 2 ml CH2Cl2 was stirred for 24 h at 40 °C. After dilution with 10 ml CH2Cl2, the
Results
2-Phenylthiophene (2PT), partially tritiated at position 5, [5-3H]-2-phenylthiophene, was incubated with liver microsomes from β-naphthoflavone-pretreated rats in the presence of NADPH. Analysis of the incubation mixture by HPLC–MS showed the major formation of two 2-phenylthiophene-S-oxide dimers, 2PTSOD, that should result from the Diels–Alder type dimerization of 2-phenylthiophene-S-oxide. These 2PTSOD metabolites were fully characterized by their mass and 1H NMR spectra, by comparison with
Discussion
The aforementioned results provide a supplementary evidence for the intermediate formation of thiophene-S-oxides in the microsomal oxidation of thiophene derivatives. As previously described in the case of thiophene itself [16] and of the thiophene-containing drug, ticlopidine [17], 2PT is oxidized by liver microsomes, with the formation of thiophene-S-oxide dimers resulting from Diels–Alder dimerization of the corresponding thiophene-S-oxide intermediate. As in the case of thiophene [3], [16]
Acknowledgments
We thank Amélie Chevrollier and Saniye Alrkilicarlsan, two summer students who participated in the preparation of 2PT metabolites and synthetic 2PTSOD and 2PTT.
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