Glucuronidation of racemic O-desmethyltramadol, the active metabolite of tramadol.
Eur J Pharm Sci
; 41(3-4): 523-30, 2010 Nov 20.
Article
en En
| MEDLINE
| ID: mdl-20797434
ABSTRACT
O-Desmethyltramadol, the active metabolite of analgesic tramadol, is metabolised through glucuronidation. The present study was conducted to identify the human UDP-glucuronosyltransferases (UGTs) that catalyse the glucuronidation of O-desmethyltramadol, a racemic mixture of 1R,2R- and 1S,2S-enantiomers. We developed a fast and selective liquid chromatography-mass spectrometry method to separate, analyse and quantify the diastereomeric phenolic O-glucuronides of O-desmethyltramadol. To quantify O-desmethyltramadol glucuronidation, we biosynthesised both phenolic O-glucuronides of O-desmethyltramadol and verified their structure by mass spectrometry and nuclear magnetic resonance spectroscopy. Subsequently, the 16 human UGTs of subfamilies 1A and 2B were screened for O-desmethyltramadol glucuronidation activity. UGTs 1A7-1A10 exhibited a strict stereoselectivity, exclusively glucuroniding the 1R,2R-enantiomer. Similar though not strict enantioselectivity was exhibited by UGT2B15. UGT2B7, on the other hand, glucuronidated both O-desmethyltramadol enantiomers, with slight preference for 1S,2S-O-desmethyltramadol. Enzyme kinetic parameters were determined for the most active UGTs, 1A8 and 2B7. The apparent K(m) or S(50) values were high 1.2mM±0.23 for 1R,2R-O-desmethyltramadol with UGT1A8 and 1.84±1.2 and 4.6±2.0mM for 1S,2S- and 1R,2R-O-desmethyltramadol enantiomers with UGT2B7, respectively. Glucuronidation analyses of O-desmethyltramadol with human liver microsomes exhibited stereoselectivity, favouring the 1S,2S-O-desmethyltramadol over 1R,2R-O-desmethyltramadol and yielding 62.4 and 24.6pmol/mg/min, respectively. In intestinal microsomes, on the other hand, the two enantiomers were glucuronidated at similar rates, about 6pmol/mg/min. The results shed new light on both tramadol metabolism and the substrate selectivity of the human UGTs.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Tramadol
/
Glucuronosiltransferasa
/
Glucurónidos
Límite:
Humans
Idioma:
En
Revista:
Eur J Pharm Sci
Asunto de la revista:
FARMACIA
/
FARMACOLOGIA
/
QUIMICA
Año:
2010
Tipo del documento:
Article
País de afiliación:
Finlandia