Structural characterization and hepatoprotective activity of a polysaccharide from Sesbania cannabina roots

First isolation of the polysaccharide from S. cannabina root. • It alleviates ethanol-induced cytotoxicity and oxidative stress in HepG2 cells. • SCPC-2 ameliorates ethanol metabolism by regulating ADH, ALDH, and CYP2E1 enzymes. • It activates the Keap1-Nrf2/HO-1 pathway to reduce oxidative stress and lipid peroxidation. • Provides a strategy for valorization of S. cannabina roots as functional ingredients. This study investigated the structural characteristics, conformational features, and hepatoprotective activity of a polysaccharide (SCPC-2) isolated from the roots of Sesbania cannabina , an underutilized industrial crop widely distributed in saline-alkaline regions. SCPC-2 exhibited an average molecular weight of 7.97 kDa and was composed mainly of mannose, galactose, rhamnose, glucose, arabinose, glucuronic acid, and galacturonic acid. Methylation analysis revealed that SCPC-2 contained diverse glycosidic linkages, including t-Man(p), t-Gal(p), t-Glc(p), and various branched residues, indicating a structurally complex architecture. NMR spectroscopy revealed characteristic oxygenated sugar-ring signals and representative H/C correlations, supporting the general carbohydrate structural features of SCPC-2. In vitro cell model assays demonstrated that SCPC-2 significantly improved the viability of ethanol-injured HepG2 cells. It reduced the levels of transaminases (ALT and AST) and the lipid peroxidation product MDA, while elevating the levels of antioxidants (SOD and GSH) and ethanol metabolism-related enzymes (ADH and ALDH). Mechanistic studies indicated that SCPC-2 alleviated ethanol-induced HepG2 cell damage by coordinately regulating ethanol metabolism and enhancing antioxidant defense via activation of the Keap1-Nrf2/HO-1 signaling pathway. These findings suggest that SCPC-2 may be a promising hepatoprotective agent, highlighting the potential for high-value utilization of S. cannabina roots.