A novel polysaccharide in Polygonatum kingianum: structure elucidation, the activities of anti-inflammatory and the regulation of gut microbiota in vitro

Polysaccharides are the primary active constituents of Polygonatum kingianum Coll. et Hemsl. However, the comprehensive characterization of P. kingianum polysaccharides (PKP) remains scarce, impeding investigations into the structure-activity relationship. In this study, a novel polysaccharide, PKP1, was purified using Cellulose DE-52 and Sephadex G-50 column chromatography, and its complete structure was elucidated through monosaccharide composition analysis, methylation analysis, as well as 1D and 2D NMR analysis. The results revealed that PKP1 primarily comprised Fru and Glc, exhibiting a molecular weight of 5.3 × 10³ Da and a polymer dispersity index of 1.20. The completed structure of PKP1 consisted of β-D-Fruf-(2 → , → 1,2)-β-D-Fruf-(6 → , → 1)-β-D-Fruf-(2 → and → 1)-α-D-Glcp-(6 → as the main chain sugar residues, with β-D-Fruf-(2 → and → 2)-β-D-Fruf-(6 → serving as the side chains sugar residues. The detailed structure of PKP1 suggested it is a novel Fru-dominated neutral polysaccharide. Biological assays indicated that PKP1 significantly reduced the levels of NO, IL-6, and TNF-α in RAW264.7 macrophages, while also exerting regulatory effects on the gut microbiota structure and its metabolites in vitro. Our findings enriched the understanding of the structural characteristics of P. kingianum polysaccharides and laid a solid foundation for considering P. kingianum as a potential functional food supplement.