Biosynthesis and stereoselective analysis of (−)- and (+)-zaltoprofen glucuronide in rat hepatic microsomes and its application to the kinetic analysis

Zaltoprofen, available commercially as a racemic mixture, is a propionic acid derivative of non-steroidal anti-inflammatory drugs (NSAIDs). Firstly, (+)- and (−)-zaltoprofen glucuronide was biosynthesized and purified. Then a simple and rapid RP-HPLC analysis method for direct determination of (+)- and (−)-zaltoprofen glucuronide in rat hepatic microsomes was developed and validated. The calibration curves of (+)- and (−)-zaltoprofen glucuronide both showed good linearity in the concentration range from 0.15 to 31.13 μM. The lower limit of quantification was 0.15 μM. Finally, this method was used to investigate the enantioselectivity of zaltoprofen glucuronidation in rat hepatic microsomes. The kinetics of zaltoprofen glucuronidation in rat hepatic microsomes for 40 min incubation fit the Michaelis–Menten model. Kinetic analysis indicated that (−)-zaltoprofen had a higher glucuronidation rate in rat liver microsome than that of (+)-zaltoprofen. The catalyzing efficiency (Vmax/Km) ratio of (+)-zaltoprofen to (−)-enantiomer is 0.8 times in rat liver microsomes.