Potential of tormentil rhizome ethanolic extract and its postbiotic metabolites for inhibiting enterotoxigenic E. coli growth: Implications for functional food applications

Tormentil rhizome ethanolic extract (TREE), rich in polyphenols, used in beverages and known for gastroprotective properties, represents a promising plant-based ingredient for functional food development. After ingestion, TREE undergoes metabolism by gut microbiota, generating bioactive postbiotic metabolites (TGMs). TREE/TGMs might be effective against enterotoxigenic Escherichia coli (ETEC) - a major cause of diarrhea and intestinal barrier dysfunction. This study evaluated the antimicrobial and antiadhesive properties of TREE and TGMs using in vitro, postbiotic, and ex vivo microbiota models. TREE showed dose-dependent ETEC inhibition, with complete suppression at 5 mg/mL. At lower concentrations, both TREE and TGMs delayed the lag phase, reduced growth rate, and impaired adhesion to intestinal epithelial cells. Notably, TGMs retained activity in complex environments such as fecal water and microbiota cultures, though efficacy varied with microbiota composition. These findings support the potential of TREE in functional foods or dietary supplements targeting gut health and ETEC-related disorders.