Preparation and Physicochemical Properties of <i>Gynura divaricata</i> (L.) DC Polysaccharides and Their Regulating Activities on Human Gut Microbiota

In this study, a convenient and highly efficient ascorbic acid-hydrogen peroxide_-assisted method was developed for the extraction of polysaccharide from Gynura divaricata (L.) DC (GDP), and the extraction yield reached 21.05% under optimized extraction conditions, which was significantly higher than that by conventional hot water extraction (12.32%). The GDP was separated and purified by DEAE-52 ion exchange column and Sephadex G-100 gel column. The physicochemical properties of GDP and its two purified components were characterized. Monosaccharide composition assay indicated that GDPs were mainly composed of galactose, xylose, and arabinose. The molecular weight of GDP, GDP1, and GDP3 was determined as 15.75, 9.83, and 8.04 kDa, respectively. GDPs were found to possess a good viscoelastic property. Using an in vitro simulated human fermentation model, the regulatory effects of GDPs on the human intestinal flora were assessed by16S rDNA sequencing and bioinformatics techniques. GDPs were found to be degraded and utilized by intestinal microorganisms, while promoting the production of short chain fatty acids. GDPs efficiently regulated the structure of intestinal flora by increasing the abundance of beneficial bacteria (such as Bifidobacterium, Bacteroides and Lactobacillus) and reducing the abundance of harmful bacteria. Therefore, GDPs developed in this work have potential as prebiotics.