Simulated Digestion and Fecal Fermentation Characteristics of Pumpkin Polysaccharide and the Anti‐Inflammatory Activity of Its Fermentation Products

Polysaccharides are recognized for their prebiotic effects and substantial impact on human health. This study aimed to investigate the digestion and fermentation properties of a purified pumpkin polysaccharide (PPS3) and its effects on gut microbiota. PPS3 maintained its molecular weight during simulated oral, gastric, and intestinal digestion, with no significant increase in reducing sugars or free monosaccharides, indicating strong resistance to enzymatic hydrolysis. During 48-h in vitro fermentation with human fecal microbiota, PPS3 was efficiently degraded, leading to a 66.7% decrease in reducing sugar content and a significant pH reduction compared to the blank control (fermentation medium without PPS3). Total short-chain fatty acid (SCFA) concentration increased by 24.29% in the PPS3 group (33.47 ± 0.99 mM) versus control (26.93 ± 0.80 mM). PPS3 selectively modulated gut microbiota composition by decreasing the Firmicutes to Bacteroidota ratio and enriching beneficial taxa. Additionally, a significant positive correlation was observed between SCFA production and specific bacterial strains. Notably, PPS3 fermentation supernatants significantly inhibited pro-inflammatory mediators TNF-α, IL-6, and nitric oxide (NO) while upregulating IL-10 in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. These findings demonstrate that PPS3 resists digestion, promotes beneficial microbial metabolism, and exerts anti-inflammatory effects, supporting its potential application as a functional prebiotic for gut and systemic health.