Background: Sulfonamide antibiotics are the second most frequent cause of allergic drug
reactions (after the β-lactams). Activity and side effects of sulfonamide may be attributed to their metabolites.
To the best of our knowledge there is no in vitro metabolism study for sulfamerazine (SMR)
available in the literature. The main objectives of this research are to develop an analytic method for
screening, identifying and quantifying SMR and its active metabolites and for in vitro metabolism study.
Methods: An ultra performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometric
(UPLC-QTOF-MS) method was used for establishing the accurate mass databases of SMR
and N-ASMR as well as non-target analytes and for in vitro screening, identification, and quantification
of SMR and its metabolites N4-acetylsulfamerazine (N-ASMR) in mice liver homogenates.
Result: The limit of detection (LOD) and limit of quantification (LOQ) were 1.0 and 5.0 µg L-1 for
SMR and 12.0 and 20 µgL-1 for N4-acetylsulfamerazine (N-ASMR), respectively. Peak area intra-day
RSD (n=6) and inter-day RSD (n=9) were 5.0 and 8.2 % for SMR, and 4.3 and 7.2% for N-ASMR,
respectively. The identification of targeted analytes (SMR and N-ASMR) was conducted based on the
established accurate mass database (both retention time and accurate mass). SMR could be metabolized
via acetylating by acetoacetyl coenzyme A, and two isomers of ASMR were confirmed. Methylation of
SMR was found, and four isomers of a metabolite of SMR were confirmed.
Conclusion: The developed UPLC-QTOF-MS method is rapid and effective for screening, identification,
and quantification of SMR and its metabolites. The metabolism mechanism and accurate mass
databases for target and non-target metabolites of SMR in mice liver are valuable for metabolism study,
with high accurate mass.