Preparation, structural characterization and in vitro activity of ginger polysaccharide

Abstract A polysaccharide was extracted from the fresh ginger by water extraction and alcohol precipitation. A homogeneous polysaccharide was obtained by Sevage deproteinization, dialysis, DEAE-52 ion exchange chromatography and Sephadex G-100 gel column chromatography. The molecular weight of the ginger polysaccharide was determined by high performance gel permeation chromatography. The monosaccharide composition, scanning electron microscope and other physicochemical parameters of the ginger polysaccharide were further determined. The spectral properties of the ginger polysaccharide were investigated by ultraviolet and infrared spectroscopy. On this basis, methylation analysis, 1D and 2D NMR analysis were used to investigate its possible chemical structure. The results showed that the ginger polysaccharide group was divided into neutral polysaccharide components with high homogeneity, M w = 35.52 kDa, M n = 216.56 kDa and the sugar content was 93.5%. The ginger polysaccharide is mainly composed of Fuc, Ara, Rha, Gal, Glc, Xyl, Man, Gal-UA and Glc-UA, the amount of substance ratio was 1.01:1.96:9.54:14.82:64.20:3.84:2.07:1.41:1.16. To study the structure–activity relationship of ginger polysaccharide, acetylated ginger polysaccharide and phosphate ginger polysaccharide were prepared by chemical methods in this study. The results of antioxidant activity in vitro showed that the ginger polysaccharide and its derivatives had good biological activity in freeing ABTS + radical scavenging, freeing hydroxyl radical scavenging, freeing DPPH radical scavenging and reducing ability. Interestingly, the results showed that the ginger polysaccharide had a certain inhibitory effect on the growth of E. coli in vitro. In general, this study provides a certain experimental basis and reference for the further research on the activity of ginger polysaccharide and its derivatives. Graphical Abstract