Identification of metabolites of lobeline in the rat urine by liquid chromatography-tandem mass spectrometry

This is a report about the analysis of lobeline and its metabolites in rat urine by using high-performance liquid chromatography-electrospray ionization ion trap tandem mass spectrometric method (LC/MSn). The urine of healthy rat were sampled from 0 to 24 h after administered a single dose of lobeline (3 mg/kg) by oral gavage, then centrifuged at 10,000 rpm for 10 min to get the supernatants. The supernatants were purified by solid-phase extraction (SPE) with a C18 cartridge. After the above purified process, the purified urine were injected into a reversed-phase C18 column with mobile phase of methanol/water (70:30, v/v, adjusted to pH 3.5 with formic acid) and detected by an on-line MSn system. The identification and structural elucidation of the metabolites were performed by comparing their changes in molecular mass (ΔM), full-scan MSn spectra with those of the parent drug. Ten metabolites of lobeline were found in rat urine. All the metabolites were reported for the first time.