Linarin, a flavone glycoside, is considered to be a promising natural product due to its diverse pharmacological activities, including analgesic, antipyretic, anti-inflammatory and hepatoprotective activities. In this research, the metabolites of linarin in rat intestinal flora and biosamples were characterized using ultra-high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS/MS). Three ring cleavage metabolites (4-hydroxybenzoic acid, 4-hydroxy benzaldehyde and phloroglucinol) were detected after linarin was incubated with rat intestinal flora. A total of 17 metabolites, including one ring cleavage metabolite (phloroglucinol), were identified in rat biosamples after oral administration of linarin. These results indicate that linarin was able to undergo ring fission metabolism in intestinal flora and that hydrolysis, demethylation, glucuronidation, sulfation, glycosylation, methylation and ring cleavage were the major metabolic pathways. This study provides scientific support for the understanding of the metabolism of linarin and contributes to the further development of linarin as a drug candidate.

Linarin, a flavone glycoside, is considered to be a promising natural product due to its diverse pharmacological activities. Recently, it has been brought into focus for its potential to treat liver failure. In this study, a rapid and sensitive liquid chromatography electrospray-ionization tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of linarin and its three metabolites (acacetin, apigenin, and p-hydroxy benzaldehyde) in plasma and liver tissue samples of normal rats and rats with d-galactosamine (d-GalN)-induced liver injury. After liquid–liquid extraction (LLE) with ethyl acetate, chromatographic separation of the four analytes was achieved using an ACQUITY UPLC BEH-C18 (1.7 μm, 2.1 × 50 mm) with a mobile phase of 0.01% formic acid in methanol and 0.01% formic acid at a flow rate of 0.3 mL/min. The detection was accomplished on a tandem mass spectrometer via an electrospray ionization (ESI) source by multiple reaction monitoring (MRM) in the negative ionization mode. The method had a good linearity over the concentration range of 1.00–200 ng/mL for linarin and its metabolites. The validated method was successfully applied to the pharmacokinetic and liver tissue distribution study of linarin and its metabolites after a single oral administration of linarin (90 mg/kg) to rats.

Physalin A is a promising natural product with excellent anti-inflammatory and anti-tumor activities. However, the pharmacokinetic profile of physalin A is still unclear. In this study, a rapid and sensitive analytical method based on LC–MS/MS for the quantitation of physalin A in rat plasma with special consideration to its chemical stability was developed and validated. To avoid the degradation of physalin A, the separation of plasma was conducted at 4 °C directly after the blood samples were collected. Meanwhile, plasma samples were immediately precipitated with acetonitrile containing tolbutamide (internal standard, IS) and the pH of the supernatant was adjusted to 1.5 with formic acid. Chromatographic separation of physalin A and IS was achieved on an ACQUITY UPLC BEH-C18 column (2.1 × 50 mm, 1.7 μm) using 0.1% formic acid and acetonitrile as mobile phase delivered at 0.3 mL/min in a gradient elution mode. Physalin A and IS were detected through negative ion electrospray ionization in multiple reaction monitoring (MRM) mode. The MS/MS ion transitions for physalin A and IS were m/z 525.1–148.9 and m/z 269.8–169.9, respectively. The developed method showed good linearity over the range of 2.00–400 ng/mL. This method was successfully applied to the pharmacokinetic study of physalin A in rats following its intragastric administration and the findings were beneficial for future studies of physalin A.