Huangqin decoction ameliorates DSS-induced ulcerative colitis: Role of gut microbiota and amino acid metabolism, mTOR pathway and intestinal epithelial barrier

•HQD ameliorates DSS-induced ulcerative colitis.•HQD regulates gut microbiota and amino acid metabolism and mTOR signaling pathway and repairs epithelial barrier.•Intestinal metabolites inhibited the apoptosis of DSS-induced FHC cells.•Intestinal metabolites activate the mTOR signaling pathway and restore the epithelial barrier function.•Protective mechanism of metabolites regulated by HQD is similar to HQD.