Screening of Intestinal Bacterial Metabolites of Platycodin D Using Ultra-Performance Liquid Chromatography/Quadrupole Time-of-Flight Mass Spectrometry.

Platycodin D (PD), a bioactive triterpenoid saponin isolated from Platycodi Radix (PR), possesses a vast range of biological activities. Although the pharmacological activities and pharmacokinetics of PD have been well demonstrated, information regarding the intestinal metabolisms of PD is very limited. In this study, human and rat fecal microflora were prepared and anaerobically incubated with PD at 37[Formula: see text]C for 48[Formula: see text]h, respectively. A highly sensitive and specific ultra performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) was developed for the analysis of PD and related metabolites in the reaction samples. A Liquid-liquid extraction method was used for sample pretreatment and the chromatographic separation was performed on a 1.7 [Formula: see text]m particle size Syncronis C[Formula: see text] column using gradient elution system. Finally, a total of seven metabolites were detected and tentatively identified, such as the demethylation metabolite (M1), deoxidation metabolites (M3, M7) and hydrolysis at the C-28 oligosaccharide metabolites (M5, M6), which were first discovered in this experiment. The results indicate that hydrolysis, demethylation, dehydroxylation, and acetylation were the major metabolic pathways of PDin vitro. Additionally, four bacterial strains from human feces including Enterococcus sp.41, Bacillus sp.46, Escherichia sp.49 A and Escherichia sp.64 were detected and further identified with 16S rRNA gene sequencing due to their relatively strong metabolic capacity toward PD. The present study provides important information about the metabolism of PD, which will help elucidate the impact of intestinal bacteria on this active component.