Shenling Baizhu San ameliorates ulcerative colitis by regulating the gut microbiota and its tryptophan metabolites: A complementary medicine to mesalamine

Shenling Baizhu San (SBS) is commonly employed to improve gastrointestinal dysfunction in patients with ulcerative colitis (UC) in China. SBS combined with mesalamine has been demonstrated to result in improve its curative effects without increasing any adverse reactions, but the underlying mechanism remains unclarified.Our study aimed to illuminate the potential therapeutic effects and mechanisms of SBS, which is a medicine complementary to mesalamine, in the treatment of UC.A prospective cohort study was conducted to evaluate the efficacy of SBS as a complementary medicine to mesalamine for patients with UC (n = 48). The patients in the control group (n = 24) were given mesalamine alone, whereas those in the experimental group were administered mesalamine combined with SBS. The therapeutic outcome was assessed at 8 weeks. The structures of the gut microbiota (GMB) were characterized by 16S rRNA sequencing, and the microbial tryptophan metabolites were analyzed by UPLC-MS/MS to investigate the mechanism through which SBS achieves its effects.Our results showed that the combination of SBS and mesalamine could significantly improve the clinical signs of UC by achieving mucosal healing and relieving colon damage. Interestingly, the combination of SBS and mesalamine could alter the GMB structures and increase the microbial levels of tryptophan metabolites, including indole-3-propionic acid and indole-3-acetic acid.SBS combined with mesalamine is effective in improving the clinical and endoscopic outcomes of patients with UC. SBS, as a complementary therapy to conventional treatment, alleviates UC via the GMB-tryptophan metabolite axis.