Metabolites identification and reversible interconversion of chelerythrine and dihydrochelerythrine in vitro/in vivo in rats using ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.

Chelerythrine (CHE) and dihydrochelerythrine (DHCHE), two typical benzophenanthridine alkaloids, have a wide range of pharmacological activities, such as antibacterial, anti-tumour and antiparasitic activities. To date, the biological activities of CHE and DHCHE are well reported, but the biotransformation of CHE and DHCHE in vivo remains unknown. This study aims to clarify the metabolic pathway of CHE and DHCHE in rat liver microsomes (RLMs) in vitro and in vivo. An ultra-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC/ESI-QTOF-MS) method was developed for metabolites identification of CHE and DHCHE. The urine, feces, bile, and plasma samples and RLMs samples were collected for analyzing the biotransformation pathway of CHE and DHCHE. The result showed that there is a phenomenon of mutual reversible interconversion between CHE and DHCHE in vivo and in vitro. The other biotransformation pathways of CHE and DHCHE including demethylation, hydroxylation, methylene dioxy cycle opening, and glucuronidation mainly occurred in the side chain of benzophenanthridine parent structure. Twenty-five phase I and eight phase II metabolites of CHE, twenty-two phase I and eight phase II metabolites of DHCHE were detected. The results will help to develop a deeper understanding of CHE and DHCHE in vivo process and provide some references for the biotransformation research of other benzophenanthridine alkaloids.