Mass spectrometric analyses of urinary clomiphene and toremifene metabolites in doping control by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF)

Clomiphene and toremifene, two chlorine-containing selective estrogen receptor modulators (SERMs) with a common triphenylethylene structure, are prohibited by World Anti-Doping Agency (WADA) out-of-competition and in-competition. In this paper, we investigated the metabolic pathway and different drug metabolites in human urine collected from healthy volunteers by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF) with accurate mass measurement. Four unreported metabolites of toremifene at m/z 418.2015 and 456.1937 and three clomiphene metabolites at m/z 482.2094 and 468.1936 were detected in positive full scan mode using an electrospray ionization source, and further structural elucidation was carried out in targeted MS/MS mode. Based on the fragmentation pattern observed for those metabolites available as reference standards, the chemical structures of these unreported metabolites were identified. Of all these new metabolites, an unordinary dimethoxylated metabolite of clomiphene was first reported.