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Identification of Sophoridine and Its Metabolites in Rat Urine by Liquid Chromatography-Tandem Mass Spectrometry

Sophoridine is an important quinolizidine alkaloid which has wide pharmacological effect including antiarrhythmia, antitumor, immunological enhancement, and immunosuppression. In this work, a rapid, sensitive and dependable liquid chromatographic–electrospray ionization (ESI) tandem ion trap mass spectrometric method has been developed for identification of sophoridine and its metabolites in rat urine after administration of a single dose of sophoridine (12 mg/kg) by vena caudalis injection. The rat urine samples were purified by use of a C18 solid-phase extraction cartridge, then chromatographically separated by a reversed-phase C18 column (Aichrom ReliAsil C18, 5 μm, 2 mm × 150 mm i.d.) with 70:30(v/v) methanol-0.01% triethylamine solution (adjusted to pH 3.5 with formic acid) as mobile phase and detected by an on-line ESI ion trap MS-MS detector. Identification and structural elucidation of the metabolites were performed by comparing the molecular weights, retention-times, and MS-MS spectra of them with those of the parent drug. As a result, six phase I metabolites of sophoridine (N-oxide metabolite, mono-hydroxylation metabolite, hexa-dehydrogenation metabolite and three di-dehydrogenation metabolites) were identified in rat urine for the first time.