A galacturonic acid-rich polysaccharide from Citrus medica 'fingered' alleviated the dextran sulfate sodium-induced ulcerative colitis

Ulcerative colitis (UC) treatment is often limited by adverse reactions and high recurrence rates, highlighting the need for safer, more effective therapies. Citrus medica 'Fingered' (C. medica), known for its anti-inflammatory properties, remains underexplored, particularly its polysaccharide components. This study investigated the intestinal protective effects of C. medica polysaccharides extracted via hot water (HWE-CP) and characterized a primary fraction's structure. The dextran sulfate sodium -induced UC mouse model was used to evaluate the intestinal protective activity of HWE-CP, and one of the main fractions was characterized using HPGPC, HPAEC, FTIR, TGA, methylation, and NMR. The results indicated HWE-CP alleviated the UC symptoms in mice by reducing weight loss and disease activity, increasing colon length, minimizing intestinal mucosal damage, strengthening the intestinal barrier, lowering inflammatory factor expression, and balancing gut flora. The primary fraction, HWE-CP-2A, had a molecular weight of 38.28 kDa and comprise Rha, Ara, Gal, and GalA with molar rations of 1.57: 4.46: 2.50: 91.47. Its main chain was →[4)-α-D-GalAp-6-O-CH₃(1]5 → 3,4)-α-D-GalAp-6-O-CH₃, with α-D-GalAp-(1→) linked to the main chain via the C-3 bond. The polymerization degree was around 25. This study provides evidence for the structural with anti-UC relationships of HWE-CP and lays the foundation for the development of its related products.