Purification, structural identification of polysaccharides from Hangzhou chrysanthemum and their α-glucosidase inhibition mechanisms

Hangzhou chrysanthemum is a medicinal plant with food-related properties, and the hypoglycemic components of its natural polysaccharides and their related mechanisms are not yet fully understood. This paper purified the crude Hangzhou chrysanthemum polysaccharides (HCPs) via DEAE-52 and Sephadex-G150 column chromatography to finally obtain a major homogeneous polysaccharide fraction (HCPs-3-SG), and then the structure of HCPs-3-SG was characterized by HPGPC, FT–IR, GC-MS NMR, CD, TGA, etc. Finally, the α-glucosidase inhibitory mechanisms of HCPs-3-SG were investigated through comprehensive experiments and simulation methods. The results show that HCPs-3-SG with an Mw of 7.85 kDa consisted of Fuc (1.42 %), Rha (6.89 %), Ara (7.22 %), Gal (5.55 %), Glc (1.67 %), Xyl (2.09 %), Man (1.37 %), and Gal-UA (73.80 %). →4)-α- D -GalUA(6-OCH 3 )-(1→ and →4)-α- D -GalUA-(1→ was the primary chain of HCPs-3-SG. Moreover, HCPs-3-SG didn’t has a triple helix structure and contained microcrystalline structures, irregular fragments, and reticular segment structures. HCPs-3-SG presented a random linear chain, multi-branched structure, and spindle-shaped protrusions. Furthermore, HCPs-3-SG exhibited a strong inhibitory effect on α-glucosidase activity. The α-glucosidase-HCPs-3-SG complex remained stable in terms of RMSD, RMSF, and turnaround radius in the Gromacs simulation. HCPs-3-SG played a crucial role in the binding process with α-glucosidase by interacting with amino acid residues Tyr158, Phe303, Arg315, and Arg442.