Insight into the mechanism of Xiao–Chai–Hu–Tang alleviates irinotecan-induced diarrhea based on regulating the gut microbiota and inhibiting Gut β-GUS

•Xiao–Chai–Hu–Tang attenuates irinotecan-induced diarrhea by mediating gut microbiota.•Xiao–Chai–Hu–Tang attenuates irinotecan-induced diarrhea by inhibiting gut β-GUS.•Xiao–Chai–Hu–Tang significantly reduced the concentration of SN-38 in the gut.•Xiao–Chai–Hu–Tang active ingredient baicalein selectively inhibited EcGUS activity.