Three bioactive compounds from Huangqin decoction ameliorate Irinotecan-induced diarrhea via dual-targeting of Escherichia coli and bacterial β-glucuronidase.

Irinotecan (CPT-11) is a commonly prescribed chemotherapeutic for the treatment of colon cancer. Unfortunately, acute and delayed diarrhea are prominent side effects of CPT-11 use, and this limits its therapeutic potential. The curative effect of Huangqin decoction (HQD) on chemotherapy-induced diarrhea has been proven. This study investigated the efficacy of the components of HQD (baicalein, baicalin, and paeoniflorin) on CPT-11-induced diarrhea and their underlying mechanisms. Baicalein was found to be the most effective component in improving CPT-11-induced enterotoxicity by intestinal permeability test, ELISA, fluorescence co-localization, and IHC. The combination of baicalin, baicalin and paeoniflorin can obtain similar therapeutic effect to that of HQD. Mendelian randomization analysis, 16 s rRNA sequencing, and fluorescence imaging revealed that baicalein and baicalin significantly inhibited β-glucuronidase (β-GUS) activity. Bacterial abundance analysis and scanning electron microscopy showed that baicalein inhibited the proliferation of Escherichia coli by destroying its cell wall. The molecular dynamics and site-directed mutagenesis results revealed the structural basis for the inhibition of β-GUS by baicalein and baicalin. The results above provide a new idea for the development of drug therapy for adjuvant chemotherapy and theoretical guidance for the optimization of molecular structure targeting β-GUS.