Ultrasound-assisted non-starch polysaccharide extraction from bulbils of Dioscorea opposita maxim and its bioactivity on ulcerative colitis via improving the intestinal barrier and modifying the gut microbiota.

Dioscorea opposite (D. opposita) has been extensively used in both medical and culinary applications for over 2000 centuries. Here, a response surface methodology (RSM) approach was employed in an effort to optimize the ultrasound-mediated extraction of polysaccharides from the bulbils of this species in order to facilitate the effective utilization of D. opposita and to enable more comprehensive studies of its biological and structural characteristics. Model substitution revealed that optimal conditions included a material concentration of 18.24 mL/g and ultrasound settings of 968 W and 29.09 min. Through this strategy, non-starch polysaccharides were isolated from D. opposita bulbils, subjected to structural characterization, and assessed for their effects on models of inflammatory bowel disease (IBD). Polysaccharide structural characterization was achieved through Ultraviolet spectrum (UV), infrared spectroscopy (FTIR), Gas Chromatography-Mass Spectrometer (GC-MS), and nuclear magnetic resonance (NMR) approaches. The monosaccharides found to comprise D. opposita bulbil polysaccharides (DBPs, molecular weight: 832,451 Da) included arabinose, galactose, glucose, mannose, and galacturonic acid (molar ratio = 0.139:0.701:83.397:15.363:0.401). The DBPs fractions consisted of a main chain formed by→4)-α-D-Glc (p)-(1→ and →4)-β-D-Man (p)-(1→, and branches formed at the 6th position of some Glc residues. The main glucose residues of the branch sites are α-D-Glc(p) -(1→, with a small amount of α-D-Glc(p)-(1 → 6)-α-D-Glc(p)-(1→. Animal model studies revealed that relative to model controls, DBPs treatment was associated with significant improvements in terms of body weight, histopathological damage, colon shortening, and overall disease activity. Through 16S rRNA sequencing and metabolomics analyses, DBPs treatment was predicted to alleviate IBD through the restructuring of the intestinal microflora and the enhancement of gut microbiota-associated tryptophan metabolism.