S-Naproxen-β-1-O-acyl Glucuronide Degradation Kinetic Studies by Stopped-Flow High-Performance Liquid Chromatography-1H NMR and High-Performance Liquid Chromatography-UV

• Published in: Drug metabolism and disposition Vol. 29; no. 4; p. 375
• Main Authors: Rasmus W. Mortensen, Olivia Corcoran, Claus Cornett, Ulla G. Sidelmann, John C. Lindon, Jeremy K. Nicholson, Steen Honoré Hansen
• Format: Journal Article
• Language: English
• Published: American Society for Pharmacology and Experimental Therapeutics 01.04.2001
• ISSN: 0090-9556; 1521-009X

Acyl-migrated isomers of drug β-1- O -acyl glucuronides have been implicated in drug toxicity because they can bind to proteins. The acyl migration and hydrolysis of S -naproxen-β-1- O -acyl glucuronide ( S -nap-g) was followed by dynamic stopped-flow HPLC- 1 H NMR and HPLC methods. Nine first order rate constants in the chemical equilibrium between six species ( S -nap-g, its α/β-2- O -acyl, α/β-3- O -acyl, α/β-4- O -acyl, and α-1- O -acyl-migration isomers, and S -naproxen aglycone) were determined by HPLC-UV studies in 25 mM potassium phosphate buffer, pH 7.40, 25 mM potassium phosphate buffer in D 2 O pD 7.40, and 25 mM potassium phosphate buffer in D 2 O pD 7.40/MeCN 80:20 v/v (HPLC- 1 H NMR mobile phase). In the 25 mM potassium phosphate buffer (pH 7.40) the acyl-migration rate constants (h −1 ) were 0.18 ( S -nap-g–α/β-2- O -acyl isomer), 0.23 (α/β-2- O -acyl–α-1- O -acyl), 2.6 (α-1- O -acyl–α/β-2- O -acyl), 0.12 (α/β-2- O -acyl–α/β-3- O -acyl), 0.048 (α/β-3- O -acyl–α/β-2- O -acyl), 0.059 (α/β-3- O -acyl–α/β-4- O -acyl), and 0.085 (α/β-4- O -acyl–α/β-3- O -acyl). The hydrolysis rate constants (h −1 ) were 0.025 (hydrolysis of S -nap-g) and 0.0058 (hydrolysis of all acyl-migrated isomers). D 2 O and MeCN decreased the magnitude of all nine kinetic rate constants by up to 80%. The kinetic rate constants for the degradation of S -nap-g in the mobile phase used for HPLC- 1 H NMR determined using HPLC-UV could predict the results obtained by the dynamic stopped-flow HPLC- 1 H NMR experiments of the individual acyl-migrated isomers. It is therefore recommended that β-1- O -acyl glucuronide degradation kinetics be investigated by HPLC-UV methods once the identification and elution order of the isomers have been established by HPLC- 1 H NMR.