Anti-dyspeptic effects and comparative structural analysis of polysaccharides from hulled and hulless barley-based...

Pan-roasted Hordei Fructus Germinatus (RHFG), traditionally prepared from germinated and dried barley grains, is widely used for its digestion-promoting properties. This study aimed to isolate and characterize polysaccharides from RHFG derived from hulless (LBP) and hulled barley (DBP) and to evaluate their protective effects against functional dyspepsia. Two major neutral polysaccharide fractions, named pLBP and pDBP, were purified and structurally elucidated. Both were primarily composed of arabinose, glucose, and xylose units, but differed in the backbone linkages and branching architectures. Specifically, pLBP was a neutral heteropolysaccharide with a backbone consisting of →3)-β-d-Glcp-(1→, →4)-β-d-Glcp-(1→, →4)-β-d-Xylp-(1→, and →2,3,5)-α-l-Araf-(1 → residues, featuring branching points at O-2 and O-3 of Araf units and O-3 of Xylp residues. pDBP possessed a backbone of →3)-β-d-Glcp-(1 → and →4)-β-d-Glcp-(1 → residues with branching at O-3/O-4 positions. The side chains were primarily composed of →4)-β-d-Xylp-(1→, →3,4)-β-d-Xylp-(1→, and α-d-Glcp-(1 → residues. LBP and DBP significantly increased small intestinal propulsion and gastric emptying rates in functional dyspepsia mice and enhanced serum levels of excitatory neuropeptides. LBP showed a stronger digestive-promoting profile, with increased gastric acid and pepsin secretion at 84 and 168 mg/kg/d in rats. The higher branching density and distinct Araf-associated branching pattern of pLBP, compared with pDBP, potentially contributing to its enhanced gastric secretory response. Collectively, these findings indicate that polysaccharides from RHFG alleviate functional dyspepsia by promoting gastrointestinal motility and digestive secretion, providing mechanistic insight into the traditional use of RHFG as a digestion-enhancing agent.