Bistort rhizome extract enhances intestinal barrier integrity in a porcine intestinal epithelial cell model

Bistorta officinalis (Polygonaceae) rhizome has long been used in traditional medicine to treat gastrointestinal disorders such as diarrhoea and inflammation. However, the active components and molecular mechanisms underlying its effects remain insufficiently defined. The aim of the study was to characterise the chemical composition of B. officinalis rhizome, isolate major constituents, evaluate their antibacterial and anti-adhesive activity against enteric pathogens, cytotoxicity, transepithelial permeability, and effects on intestinal barrier integrity. Chemical composition of the extract was assessed using UHPLC-DAD-MSⁿ, and structure elucidation of isolated constituents was based on NMR experiments. Antibacterial activity against E. coli and S. enterica was evaluated with broth microdilution method, cytotoxicity against IPEC-J2 cells with MTT assay, and anti-adhesive activity against E. coli with flow cytometry. RSLC-Q Exactive Focus Orbitrap MS was used to assess transepithelial permeability. Impact on intestinal barrier integrity was assessed by measuring transepithelial electrical resistance of IPEC-J2 cell monolayers, and expression of tight junction proteins was evaluated with Western blotting. The extract exhibited a profile dominated by hydrolysable and condensed tannins, of which seventeen were isolated. Modest antimicrobial activity, low cytotoxicity (IC₅₀ = 410 μg/mL), and no anti-adhesive activity were observed. Low-molecular-weight phenolics permeated IPEC-J2 monolayers, whereas high-molecular-weight procyanidins did not. Both extract and isolated compounds enhanced intestinal barrier integrity. The extract upregulated occludin and tended to increase claudin-4, while a galloylated catechin dimer enhanced claudin-4 expression. Collectively, these findings indicate that B. officinalis rhizome promotes gastrointestinal health primarily by modulating expression of tight junction proteins rather than direct antimicrobial or antiadhesive properties.