Mass spectrometric characterization of toremifene metabolites in human urine by liquid chromatography-tandem mass spectrometry with different scan modes

The metabolism and excretion of toremifene were investigated in one healthy male volunteer after a single oral administration of 120 mg toremifene citrate. Different liquid chromatographic/tandem mass spectrometric (LC/MS/MS) scanning techniques were carried out for the characterization of the metabolites in human urine for doping control purposes. The potential characteristic fragmentation pathways of toremifene and its major metabolites were presented. An approach for the metabolism study of toremifene and its analogs by liquid chromatography-tandem mass spectrometry was established. Five different LC/MS/MS scanning methods based on precursor ion scan (precursor ion scan of m/z 72.2, 58.2, 44.2, 45.2, 88.2 relative to five metabolic pathways) in positive ion mode were assessed to recognize the metabolites. Based on product ion scan and precursor ion scan techniques, the metabolites were proposed to be identified as 4-hydroxy-toremifene (m/z 422.4), 4'-hydroxy-toremifene (m/z 422.4), α-hydroxy-toremifene (m/z 422.4), 3,4-dihydroxy-toremifene (m/z 404.2), toremifene acid (m/z 402.2), 3-hydroxy-4-methoxy-toremifene (m/z 456.2), dihydroxy-dehydro-toremifene (m/z 440.2), 3,4-dihydroxy-toremifene (m/z 438.2), N-demethyl-4-hydroxy-toremifene (m/z 408.3), N-demethyl-3-hydroxy-4-methoxy-toremifene (m/z 438.3). In addition, a new metabolite with a protonated molecule at m/z 390.3 was detected in all urine samples. The compound was identified by LC/MS/MS as N-demethyl-4,4'-dihydroxy-tamoxifene. The results indicated that 3,4-dihydroxy-toremifene (m/z 404.2), toremifene acid (m/z 402.2) and N-demethyl-4,4'-dihydroxy-tamoxifene (m/z 390.3) were major metabolites in human urine.