Liquid chromatography-tandem mass spectrometry analysis of anisodamine and its phase I and II metabolites in rat urine

A sensitive and specific method for the analysis of anisodamine and its metabolites in rat urine by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) was developed. Various extraction techniques (free fraction, acid hydrolyses and enzyme hydrolyses) and their comparison were carried out for investigation of the metabolism of anisodamine. After extraction procedure the pretreated samples were injected on a reversed-phase C18 column with mobile phase (0.2 ml/min) of methanol/0.01% triethylamine solution (adjusted to pH 3.5 with formic acid) (60:40, v/v) and detected by MS/MS. Identification and structural elucidation of the metabolites were performed by comparing their changes in molecular masses (ΔM), retention-times and full scan MSn spectra with those of the parent drug. At least 11 metabolites (N-demethyl-6β-hydroxytropine, 6β-hydroxytropine, tropic acid, N-demethylanisodamine, hydroxyanisodamine, anisodamine N-oxide, hydroxyanisodamine N-oxide, glucuronide conjugated N-demethylanisodamine, sulfate conjugated and glucuronide conjugated anisodamine, sulfate conjugated hydroxyanisodamine) and the parent drug were found in rat urine after the administration of a single oral dose 25 mg/kg of anisodamine. Hydroxyanisodamine, anisodamine N-oxide and the parent drug were detected in rat urine for up 95 h after ingestion of anisodamine.