Ulcerative colitis is a chronic inflammatory bowel disease characterized by colonic mucosal inflammation, intestinal microflora imbalance, and intestinal permeability. It is essential to develop natural compounds with anti-inflammatory and intestinal bacterial imbalance correction properties. The brown alga Sargassum horneri is rich in polyphenols, such as fucoxanthin and chromene, which have antioxidant, anti-inflammatory, and anti-cancer properties. In results, S. horneri ethanol extract (SHE) reduced TNF-α and IL-6 levels as well as Pi3k/Mtor/S6k mRNA expression in LPS-treated RAW264.7 and Caco-2 cells. In addition, SHE treatment decreased the expression of genes associated with inflammation and the mTOR axis in the co-culture system while increasing the expression of tight junction factors. In a mouse model of dextran sulfate sodium (DSS)-induced colitis, SHE treatment improved intestinal length, histological scores, and the expression of genes related to tight junctions while decreasing the expression of genes related to inflammatory markers and the mTOR axis. The gut microbiota of mice treated with SHE exhibited a decrease in the ratio of Firmicutes to Bacteroidota, which had been increased by DSS treatment and an increase in beneficial bacteria. Therefore, SHE consumption may be a useful natural alternative, as it improves gut microbiota, alleviates colitis symptoms, and prevents their onset.

Ulcerative colitis (UC), an inflammatory bowel disease (IBD) linked to colon cancer, needs effective natural preventive and therapeutic strategies to alleviate its clinical course. This study investigated the combined effects of phlorotannins (TAs) isolated from Eisenia bicyclis (E. bicyclis) and Lactobacillus casei (LC) on inflammatory markers in UC, with a focus on the aryl hydrocarbon receptor (AhR) axis. In vitro experiments revealed anti-inflammatory effects of the phlorotannin fraction isolated from E. bicyclis, especially in synergy with LC. In vivo experiments showed that a synbiotic combination of TAs and LC mitigated DSS-induced colitis and reduced intestinal shortening and splenic hypertrophy. The TA and LC combination suppressed inflammatory factors (IL-6, TNF-α, Lipocalin 2), while activating tight junction genes (Muc2, Zo-1, Occludin, and Claudin1) and enhancing antioxidant capacity (Nrf2 and Nqo1 genes). Activation of the AhR pathway, which is crucial for regulating intestinal inflammation via IL-22, was evident with both phlorotannin alone and synbiotic administration. The combination of TAs and LC amplified the synergistic effect on intestinal immunity and microbiota, favoring beneficial species and optimizing the Firmicutes/Bacteroidetes ratio. Overall, synbiotic use demonstrated superior preventive effects against UC, suggesting its potential benefits for improving the gut immune system through gut microbiota-derived metabolites.

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon that is associated with dysbiosis in the gut microbiota. Eisenia bicyclis, a marine alga, is known for its anti-inflammatory, antioxidant, and gut microbiota-modulating properties. This study explored the mechanisms by which a 70% ethanol extract of E. bicyclis may alleviate UC, through both in vitro and in vivo experiments. LC-MS/MS analysis revealed eckol, 7-phloroeckol, dieckol, phlorofucofuroeckol A, and fucofuroeckol as key phenolic compounds present in the extract. The administration of E. bicyclis significantly improved symptoms in a dextran sulfate sodium (DSS)-induced colitis mouse model by reducing intestinal shortening, splenomegaly, and histological scores. Both cell and animal studies demonstrated that E. bicyclis suppressed the release of inflammatory cytokines, downregulated the mRNA expression of genes related to the mTOR pathway, and reduced the p-mTOR/mTOR ratio. Microbiota analysis revealed that, while the Firmicutes/Bacteroidetes ratio was elevated in UC mice, E. bicyclis administration normalized this imbalance, with a notable increase in the abundance of beneficial probiotics such as Bifidobacterium bifidum. In conclusion, a phenolic-rich extract of E. bicyclis demonstrates significant potential as a dietary supplement to prevent and mitigate UC by modulating both the mTOR signaling pathway and gut microbiota composition.