The protective effect of hydrocinnamic acid on Crohn’s disease.

Polyphenols are promising therapeutics for Crohn’s disease (CD), yet their bioavailability is largely dependent on the gut microbiome. The bioactive metabolites, metabolic pathways, and anti-inflammatory mechanisms underlying their effects remain poorly defined. Through integrated multi-omics and dietary analysis, we identified hippuric acid as a reduced metabolite in CD patients and a biomarker of polyphenol–microbiome interactions. We further demonstrate that hydrocinnamic acid, derived from microbiome metabolism of dietary trans-cinnamic acid and subsequently converted to hippuric acid by the host, ameliorates colitis in mice via the PPAR-γ pathway. Notably, we identified Bifidobacterium breve Bbr60 and Escherichia coli FAH as novel hydrocinnamic acid producers, complementing the established pathway in Clostridium sporogenes and suggesting additional microbial contributors. Collectively, our findings establish hydrocinnamic acid as a diet-dependent, colon-produced, mild PPAR-γ agonist with the potential to minimize adverse effects associated with traditional PPAR-γ agonists. This work establishes a foundation for developing microbiota-targeted, polyphenol-based therapeutic strategies for CD patients.