A Novel Acidic Polysaccharide Rich in Galactose and Galacturonic Acid from Spatholobi caulis: Structural Characterization and Anti-Aging Effects in Caenorhabditis elegans

Spatholobi caulis is considered an important medicinal plant in traditional Chinese medicine, which has the functions of promoting blood circulation, replenishing blood, enhancing immunity, and stimulating hematopoiesis, but its bioactive polysaccharides remain underexplored. In this study, stepwise ethanol precipitation of Spatholobi caulis yielded a water-soluble polysaccharide fraction, designated SCP-50, which was selected for further structural and functional characterization due to its relatively high yield and typical pectin-like monosaccharide composition. The structural features of SCP-50 were systematically investigated, and its anti-aging effects were evaluated using the Caenorhabditis elegans model. Structural analysis combining monosaccharide composition, methylation-GC-MS, and 1D/2D NMR spectroscopy suggested that SCP-50 is primarily composed of galactose (30.5%), galacturonic acid (29.4%), arabinose (20.1%), and rhamnose (11.1%), with a homogalacturonan backbone and branched arabinan/galactan side chains. In vivo assays with C. elegans demonstrated that SCP-50 (1.0 mg/mL) extended the mean lifespan by 31.3% and the median lifespan from 10 to 14 days, without affecting reproductive capacity. It also enhanced stress resistance by reducing intracellular ROS levels (15.4%), improving survival under oxidative stress (40.6% increase), and enhancing thermotolerance (18.8% improvement in motility recovery). SCP-50 increased the mRNA expression of daf-16 (1.7-fold) and skn-1 (2.5-fold), suggesting the involvement of these stress-responsive pathways. These findings demonstrate that SCP-50 exerts anti-aging effects potentially through coordinated regulation of oxidative stress resistance and longevity pathways, positioning it as a promising candidate for further investigation as a functional food ingredient or nutraceutical.