Abstract
In a previous study, it was shown that the neurotoxic compound 1,2-diethylbenzene (1,2-DEB) is mainly hydroxylated in the alkyl chain to give 1-(2′-ethylphenyl)ethanol (1,2-EPE) and excreted in urine of rats as two glucuronide compounds (GA1 and GA2). Some findings have suggested that the two enantiomers of 1,2-EPE are formed in vivo. In the present study, a chiral high-performance liquid chromatography method was developed to separate the two enantiomers of 1,2-EPE from a synthesized racemic mixture. Absolute configuration of both enantiomers was determined after esterification with (R)-(+)-α-methoxy-α-(trifluoromethyl)phenylacetic acid and analysis of their 1H NMR spectra in CCl4 added with Eu (fod)3. The two main urinary metabolites, GA1 and GA2, from [14C]1,2-DEB-treated Sprague-Dawley rats (80 mg/kg, i.p.) were identified, after hydrolysis with β-glucuronidase from Escherichia coli, as (R) and (S) glucuronide conjugates of 1,2-EPE, respectively. In vitro hydroxylation of 1,2-DEB and glucuroconjugation of 1,2-EPE were under stereoselective control in S9 fraction or microsomes from male Sprague-Dawley rat liver. TheV max and K mconstants for (R)1,2-EPE enantiomer formation determined in S9 fraction were greater than those for the (S) enantiomer. In the plasma of bile duct-cannulated rats, the ratio was 1.2 ± 0.02 over the 1- to 4-h period after oral administration of [14C]1,2-DEB (100 mg/kg). In contrast, the glucuroconjugation rate of (S)1,2-DEB enantiomer was 4 times that of (R)1,2-EPE glucuroconjugation. A similar ratio of (R) to (S)1,2-EPE glucuronide conjugates was obtained in the plasma of bile duct-cannulated rats.
Footnotes
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Send reprint requests to: J. P. Payan, Institut National de Recherche et de Sécurité, Avenue de Bourgogne, B. P. N° 27, 54501 Vandoeuvre Cedex, France. E-mail:payanjp{at}inrs.fr
- Abbreviations used are::
- DEB
- diethylbenzene
- (R) and (S)1,2-EPE
- 1-(2′-ethylphenyl)ethanol
- GA1 and GA2
- (R) and (S)1,2-EPE glucuronides conjugates
- MTPA
- (R)-(+)-methoxy-(trifluoromethyl)phenylacetic acid
- UDPGA
- uridine-5′-diphosphoglucuronic acid
- CLu
- urinary clearance
- Hex
- hepatic extraction of unchanged 1,2-DEB in plasma
- HPLC
- high-performance liquid chromatography
- IR
- infrared spectrometry
- LIS
- lanthanide-induced shift
- MS
- mass spectrometry
- Rf
- retention factor
- Et
- elution time
- PEG
- polyethylene glycol
- THF
- tetrahydrofuran
- Received September 27, 2000.
- Accepted February 28, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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