Identification of active compound combination contributing to anti-inflammatory activity of Xiao-Cheng-Qi Decoction via human intestinal bacterial metabolism

Human intestinal bacteria play an important role in the metabolism of herbal medicines, leading to the variations in their pharmacological profile. The present study aimed to investigate the metabolism of Xiao-Cheng-Qi decoction (XCQD) by human intestinal bacteria and to discover active component combination (ACC) contributing to the anti-inflammatory activity of XCQD. The water extract of XCQD was anaerobically incubated with human intestinal bacteria suspensions for 48 h at 37 °C. A liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS) method was performed for identification of the metabolites. In addition, the anti-inflammatory effects of XCQD and biotransformed XCQD (XCQD-BT) were evaluated in vitro with cytokines in RAW264.7 cells induced by lipopolysaccharide (LPS). A total of 51 compounds were identified in XCQD and XCQD-BT. Among them, 20 metabolites were proven to be transformed by human intestinal bacteria. Significantly, a combination of 14 compounds was identified as ACC from XCQD-BT, which was as effective as XCQD in cell models of inflammation. In conclusion, this study provided an applicable method, based on intestinal bacterial metabolism, for identifying combinatory compounds responsible for a certain pharmacological activity of herbal medicines.