Physicochemical properties, in vitro digestive behavior, and fecal fermentation characteristics of a polysaccharide fraction from Triadica rotundifolia.

In this study, a polysaccharide fraction from Triadica rotundifolia (formerly Sapium rotundifolium Hemsl.), designated RSP, was obtained by hot-water extraction, ethanol precipitation, Sevag deproteinization, and sequential chromatographic purification. Its physicochemical characteristics, simulated digestive behavior, and effects on human fecal microbiota were systematically evaluated. RSP was obtained at a yield of 1.21%, and high-performance gel permeation chromatography (HPGPC) showed a dominant chromatographic peak with a weight-average molecular weight (Mw) of 322,357 Da. RSP exhibited a distinct monosaccharide composition, with arabinose, glucuronic acid, galactose, and glucose as the major monosaccharides. Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) further revealed typical polysaccharide functional groups and an aggregated, irregular morphological organization. During simulated gastrointestinal digestion, reducing-sugar equivalents changed only slightly during the salivary and gastric phases but increased markedly during the intestinal phase. The presence of RSP during in vitro fecal fermentation resulted in notable alterations in culture turbidity, progressive acidification, relative SCFA profiles, and microbial community structure. Furthermore, 16S ribosomal RNA gene sequencing revealed distinct fecal microbial community profiles among the RSP, Blank, and INU groups. In the LEfSe multigroup comparison, Bifidobacterium was identified as one of the taxa characterizing the RSP group. Collectively, these findings provide an integrated characterization of the physicochemical properties, in vitro digestive behavior, and fecal fermentation characteristics of RSP.