Structural characterization and structure-activity relationship of polysaccharides from Curcuma kwangsiensis extracted sequentially: Anti-Alzheimer's activity in an AlCl3-induced zebrafish model.

Research on polysaccharides from Curcuma kwangsiensis has primarily focused on hot-water extraction, while mechanistic investigations and structure-activity relationship (SAR) analyses remain scarce. Here, four polysaccharides (GYJ-W, GYJ-C, GYJ-Na, and GYJ-0.1 M) were obtained employing water, 0.05 M CDTA, 0.05 M Na2CO3, and 0.1 M NaOH. Their physicochemical properties and in vivo efficacy against-AD were evaluated to elucidate the SAR. Results showed that the extraction methods significantly affected GYJPs' yields (0.52-4.49%), monosaccharide compositions, molecular weight (3.06 × 104-2.29 × 105 Da), and anti-AD activities. Carbohydrate content ranged from 47.12% to 55.67%, with protein and uronic acid at 3.00%-15.58% and 3.06%-6.45%, respectively. Glucose predominated (23.97%-97.16%); GYJ-Na contained the highest fucose (48.89%) and glucuronic acid (11.58%). Despite significant composition and Mw variations, Fourier transform infrared (FT-IR) and thermal stability analyses confirmed that the core structural features of GYJPs were largely preserved. In vivo anti-AD activity assays indicated that GYJPs effectively alleviated locomotion impairments and reduced neuronal apoptosis. Mechanistically, the GYJPs restored cholinergic function, suppressed appb and mapta expression, inhibited neuroinflammation (il-6, il-1β, tnf-α), and enhanced antioxidant capacity (gstp and sod1). Correlation analysis revealed that Mw and monosaccharide composition are the two key determinants underlying the anti-AD bioactivity of GYJPs. Overall, these findings highlight GYJPs as promising multi-target AD drug candidates and support rational utilization of traditional Chinese medicine resources.