Identification of allocryptopine and protopine metabolites in rat liver S9 by high‐performance liquid chromatography/quadrupole‐time‐of‐flight mass spectrometry

Rationale Allocryptopine (AL) and protopine (PR) have been extensively studied because of their anti‐parasitic, anti‐arrhythmic, anti‐thrombotic, anti‐inflammatory and anti‐bacterial activity. However, limited information on the pharmacokinetics and metabolism of AL and PR has been reported. Therefore, the purpose of the present study was to investigate the in vitro metabolism of AL and PR in rat liver S9 using a rapid and accurate high‐performance liquid chromatography/quadrupole‐time‐of‐flight mass spectrometry (HPLC/QqTOFMS) method. Methods The incubation mixture was processed with 15% trichloroacetic acid (TCA). Multiple scans of AL and PR metabolites and accurate mass measurements were automatically performed simultaneously through data‐dependent acquisition in only a 30‐min analysis. The structural elucidations of these metabolites were performed by comparing their changes in accurate molecular masses and product ions with those of the precursor ion or metabolite. Results Eight and five metabolites of AL and PR were identified in rat liver S9, respectively. Among these metabolites, seven and two metabolites of AL and PR were identified in the first time, respectively. The demethylenation of the 2,3‐methylenedioxy, the demethylation of the 9,10‐vicinal methoxyl group and the 2,3‐methylenedioxy group were the main metabolic pathways of AL and PR in liver S9, respectively. In addition, the cleavage of the methylenedioxy group of the drugs and subsequent methylation or O‐demethylation were also the common metabolic pathways of drugs in liver S9. In addition, the hydroxylation reaction was also the metabolic pathway of AL. Conclusions This was the first investigation of in vitro metabolism of AL and PR in rat liver S9. The detailed structural elucidations of AL and PR metabolites were performed using a rapid and accurate HPLC/QqTOFMS method. The metabolic pathways of AL and PR in rat were tentatively proposed based on these characterized metabolites and early reports. Copyright © 2016 John Wiley & Sons, Ltd.