Gloiopeltis furcata is a major natural source of funoran, an agaran-type sulfated galactan. The primary repeating unit of funoran, G6S– LA (β-d-galactose-6-sulfate–3,6-anhydro-α-l-galactose), underlies its distinctive structural and functional characteristics. Due to its moderate gel strength, flexibility, and high biocompatibility, funoran serves as a promising hydrocolloid for texture modification, stabilization, and incorporation into functional food systems.

Funoran was isolated through a sequential cascade extraction process, followed by partial depolymerization via controlled auto-hydrolysis. The molecular weight distribution and structural characteristics of both native and depolymerized polysaccharides were analyzed using size-exclusion chromatography (SEC), FTIR, and NMR spectroscopy. Caco-2 cell assays revealed no cytotoxic effects upon treatment with either native or depolymerized funoran. The gene and protein expression levels of tight junction markers (Claudin-1, Occludin, and ZO-1) remained comparable to the control group, indicating that epithelial barrier integrity was preserved during polymer exposure. In contrast, cells treated with dextran sulfate sodium (DSS) showed markedly reduced expression of these tight junction proteins. Cholesterol, which is essential for maintaining intestinal tight junctions, was also significantly decreased in DSS-treated cells, while its level remained unchanged in funoran-treated cells, similar to the control group. Interestingly, the partially depolymerized funoran exhibited stronger inhibition of intestinal pathogenic bacterial growth and promoted the proliferation of probiotic bacteria more effectively than the native polymer. In vivo studies in mice demonstrated that oral administration of both native and depolymerized funoran solutions caused no observable toxicity, confirming their safety for potential food and therapeutic applications. In a DSS-induced colitis mouse model, funoran—particularly the depolymerized form—effectively prevented colon shrinkage typically seen in DSS-treated mice. Similarly, spleen enlargement associated with inflammation was alleviated in DSS-treated groups, where spleen size funoran-treated groups remaining comparable to healthy controls. Moreover, the serum concentration of the pro-inflammatory cytokine TNF-α and the expression of myeloperoxidase (MPO), a marker of inflammation, were significantly reduced in funoran-treated mice compared to DSS controls. Collectively, these results suggest that sulfated polysaccharides like funoran possess notable anti-inflammatory and gut-protective properties, with molecular weight playing a crucial role in modulating immune responses in intestinal systems