Structural Characterization and Anti-Alzheimer's Disease Effect of Polysaccharides From Stellariae Radix

Stellariae Radix, a frequently employed traditional Chinese medicine, originates from the dried roots of Stellaria dichotoma L. var. lanceolata Bge. To elucidate the structural characteristics and anti-Alzheimer's disease (AD) efficacy of S. dichotoma polysaccharides (SDP), SDP was extracted and comprehensively characterized using ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy and high-performance liquid chromatography (HPLC). The results revealed that SDP is composed of galactose, glucose, arabinose, galacturonic acid, mannose, and rhamnose at a molar ratio of 5.561:2.224:0.802:0.616:0.613:0.184. In vitro experiments demonstrated that SDP exhibited potent scavenging activities against ABTS, DPPH, and hydroxyl radicals in a dose-dependent manner, with the average scavenging rates reaching 99.07%, 89.44% and 56.43% respectively at the concentration of 5 mg/mL. In a C57BL/6J mouse model of AD, administration of SDP (50-200 mg/kg) significantly ameliorated cognitive dysfunction, increased the hippocampal levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), decreased the malondialdehyde (MDA) content, and regulated the expression of oxidative stress-related proteins, including Nrf2, Keap1 and NQO1. These findings indicate that SDP possesses antioxidant and neuroprotective properties, suggesting its potential therapeutic value for the treatment of AD.