A Sea Buckthorn Pomace Polysaccharide Mitigates H2O2-Induced Impairment of Intestinal Barrier Integrity in Caco-2 Monolayers

Oxidative stress is known to disrupt intestinal barrier integrity, whereas certain polysaccharides have demonstrated protective effects on intestinal function. This study aimed to isolate a polysaccharide from processed Hippophae rhamnoides subsp. sinensis pomace (remaining after oil and juice extraction) and evaluate its protective effect against H2O2-induced intestinal barrier dysfunction in Caco-2 cell monolayers. A polysaccharide fraction, designated SPP-0.2b, with a weight-average molecular weight (Mw) of 42.405 kDa, was successfully isolated by hot water extraction and purified using DEAE-52 cellulose and Sephadex G-100 gel chromatography. Monosaccharide composition analysis revealed that SPP-0.2b was mainly composed of rhamnose, arabinose, galactose, mannose, and galacturonic acid. Compared with the H2O2-treated group, SPP-0.2b (500 μg/mL) increased the transepithelial electrical resistance (TEER) by 76.67% and reduced basolateral FITC-dextran fluorescence intensity by 34.63% in Caco-2 monolayers. In addition, SPP-0.2b significantly increased the protein expression levels of Occludin and Zonula Occludens-1 by 79.49% and 66.75%, respectively. SPP-0.2b also reduced intracellular reactive oxygen species and malondialdehyde levels while enhancing the activities of superoxide dismutase and glutathione peroxidase. Collectively, these findings suggest that the protective effect of SPP-0.2b against H2O2-induced intestinal barrier dysfunction is associated with the maintenance of tight junction proteins and attenuation of oxidative stress. This study provides experimental evidence supporting the further investigation of SPP-0.2b as a potential functional food ingredient for intestinal health.