Preparation and chemical characterization of polyphenol-rich extract from Tsaoko Fructus: alleviation of ulcerative colitis in mice by modulating gut microbiota and suppressing the JNK1-cJun signaling.
BACKGROUND Tsaoko Fructus, a traditional Chinese medicinal herb, has long been used to alleviate gastritis and enteritis. Nevertheless, the active constituents and underlying anti-inflammatory mechanisms remain insufficiently characterized. PURPOSE This study aims to optimize a polyphenol-rich fraction (3CB) from Tsaoko Fructus, evaluate its effects against ulcerative colitis (UC), and reveal the underlying mechanisms of action. METHODS The preparation of 3CB was optimized using response surface methodology (RSM), and its major constituents were identified by LC-PDA-MS analysis. A murine UC model was established by administering dextran sulfate sodium (DSS). To evaluate the effects of 3CB on UC mice, metagenomic sequencing of the intestinal microbiome and RNA sequencing of colon tissues were conducted. The anti-inflammatory activity of 3CB and its principal constituents was further verified by quantitative real-time PCR (qPCR), Enzyme linked immunosorbent assay (ELISA), Western blotting, immunohistochemical staining, and histopathological analysis. Network pharmacology, molecular docking, and surface plasmon resonance (SPR) assays were employed to elucidate the molecular mechanisms underlying the anti-inflammatory effects of 3CB. RESULTS 3CB significantly alleviated UC symptoms in DSS-induced mice, reshaped the gut microbiota with reducing pathogenic Pseudomonadota and Deferribacterota while enriching beneficial Bacteroidota, and restored microbial amino sugar and nucleotide sugar metabolism pathways of intestinal flora. Additionally, 3CB preserved colonic oxidative phosphorylation, protected the mucus barrier, and suppressed inflammatory cell infiltration and the expression of cytokines. Seven major polyphenols were identified in 3CB, with epicatechin (3) and epiafzelechin (6) being the most abundant. Mechanistic investigation revealed that the anti-inflammatory effect of 3CB was partially dependent on the JNK1-modulated MAPK signaling pathway. JNK1 was identified as a direct target of 3CB, with epiafzelechin (6) exhibiting a high binding affinity (Kd = 10.4 μM). CONCLUSION 3CB ameliorates UC potentially through modulation of gut microbiota, protection of the mucus barrier, and JNK1-targeted anti-inflammatory effects, highlighting its potential as a protective intervention for inflammatory bowel disease (IBD).