A novel arabinogalactan extracted from Epiphyllum oxypetalum (DC.) Haw improves the immunity and gut microbiota in cyclophosphamide-induced immunosuppressed mice

A novel type I arabinogalactan (AG-I) polysaccharide (EPS) from Epiphyllum oxypetalum (DC.) Haw's flowers is hypothesized to possess immunomodulatory activity. This study investigated EPS's effects on immune functions and its potential mechanism for enhancing intestinal health in immunosuppressed mice. The results showed that supplementing EPS significantly alleviated immune organ damage, increased the thymus index (p < 0.01), and regulated the key immune factors, including the tumor necrosis factor-alpha (TNF-alpha), immunoglobulin A (IgA), and complement 3 (C3) in the liver (p < 0.05). EPS promoted the expression of intestinal immune barrier and chemical barrier proteins such as interferon-gamma (IFN-gamma) and mucin 2 (MUC2) (p < 0.05), effectively repairing intestinal damage. EPS improved the diversity and structure of intestinal microbiota in immunosuppressed mice (p < 0.05) and significantly altered the abundance of intestinal immune-related microbial taxa, including Lactobacillaceae and Lactobacillus (p < 0.01). Furthermore, EPS supplementation altered intestinal lactic acid metabolism, significantly increasing lactic acid levels by up to 3.4-fold (p < 0.01), and enhanced the expression of Gpr81, Wnt3a, and beta-catenin proteins at the bottom of the colonic crypts, which may repair the intestinal physical barrier. Overall, EPS represents a novel AG-I immunomodulatory dietary polysaccharide that enhances immunity and improves gut health.