Ultrahigh-performance liquid chromatography coupled with triple quadrupole and time-of-flight mass spectrometry for the screening and identification of the main flavonoids and their metabolites in rats after oral administration of Cirsium japonicum DC. extract.

RATIONALE: Cirsium japonicum DC., a traditional Chinese medicine, has been shown to have anti-haemorrhagic and anti-tumour effects. Pharmacological studies have demonstrated that this curative effect may be related to flavonoids. The present work aimed to screen and identify the main flavonoids and their corresponding metabolites in rats after oral administration of Cirsium japonicum DC. extract.

METHODS: A rapid and simple method based on ultrahigh-performance liquid chromatography coupled with triple quadrupole and time-of-flight mass spectrometry (UHPLC/QTOF-MS) was developed for the identification of the primary absorbing components and metabolites of the principal flavonoids. The absorbing components were first characterized, followed by the selection of representative constituents. In this study, the main flavonoids, pectolinarin, linarin and pectolinarigenin, were selected as templates to identify possible metabolites.

RESULTS: A total of 27 metabolites were detected in rat blood, urine and bile samples. A hydrolysis reaction was the first step for pectolinarin and linarin, followed by oxidation and reduction reactions. However, phase II metabolites for pectolinarin and linarin were not detected. The primary biotransformation routes of pectolinarigenin were identified as oxidation, reduction, hydrolysis, and glucuronide and glucose conjugation.

CONCLUSIONS: The metabolic pathways of pectolinarin, linarin and pectolinarigenin were summarized. This study not only proposed a practical strategy for rapidly screening and identifying metabolites but also provided useful information for further pharmacological studies and the design of new drugs based on Cirsium japonicum DC.