Buddlejasaponin IVb Alleviates DSS-Induced Ulcerative Colitis through the Nrf2/GPX4 Pathway and Gut Microbiota Modulation

Buddlejasaponin IVb (BJP-IVb), a triterpenoid saponin derived from Pleurotus ostreatus, is abundant in bioactive constituents. However, its potential therapeutic benefits and underlying mechanism of action against ulcerative colitis (UC) remain elusive. Studies performed using a mouse model of colitis caused by dextran sulfate sodium showed that BJP-IVb helped reduce symptoms of UC, such as weight loss, a higher disease activity index, shorter colon length, and colon damage. It also repaired the intestinal barrier function and suppressed inflammation. BJP-IVb activated the Nrf2/HO-1 antioxidant pathway, inhibited ferroptosis, and affected protein expression and oxidative indicators. The combined use of BJP-IVb and Nrf2 inhibitor ML385 negated the effects of BJP-IVb. In Nrf2-KO mice, the protective effects of BJP-IVb were reversed. BJP-IVb inhibited ferroptosis via the Nrf2/GPX4 axis and alleviated gut microbiota dysbiosis. In conclusion, our research validates the therapeutic and protective efficacy of BJP-IVb on ulcerative colits. Additionally, it offers new perspectives on preventing colitis by focusing on the metabolism of gut microbiota using natural substances.