Preparation of a Major Metabolite of Iguratimod and Simultaneous Assay of Iguratimod and Its Metabolite by HPLC in Rat Plasma.

study. The structure of the metabolite was identified as M2 (N-[3-(acetamido)-4-oxo-6-phenoxy-4H-chromen-7-yl]methanesulfonamide). HPLC assay was achieved on a C18 column using methanol-water containing 0.1% trifluoroacetic acid (55:45 v/v) at a flow rate of 1 mL/min with UV detection at 257 nm. Standard calibration curves were obtained in the concentration range of 0.5-20 µg/mL for iguratimod and its metabolite M2. The lower limits of detection of iguratimod and M2 in rat plasma were 0.1 and 0.25 µg/mL, respectively. The intra- and inter-day precision (RSD%) were within 5% for the two analytes. The average recoveries of the analytes were greater than 90%. In conclusion, recombinant human CYP450s whole-yeast transformation system could be successfully used to identify and prepare the major metabolite of iguratimod. The HPLC method we developed could be successfully applied to evaluate pharmacokinetics of iguratimod and its metabolite M2 in rats.