Gut microbial fermentation of garlic polysaccharide generates anti-inflammatory metabolites: Insights from in vitro fermentation, microbiome, and cellular analyses

This study aimed to investigate the structural characteristics, gut microbial utilization, and anti-inflammatory activity of a garlic polysaccharide (GP-1). Structural analyses revealed that GP-1 was a branched fructan primarily composed of a linear →1)- β -D-Fruf-(2→ backbone with partial branching at the O-6 position of Fructofuranosyl residues. GP-1 exhibited strong resistance to simulated gastrointestinal digestion but was efficiently metabolized by gut microbiota. During in vitro fecal fermentation, both carbohydrate content and pH significantly decreased, accompanied by structural changes of GP-1, including molecular weight distribution, monosaccharide composition, FTIR spectra, surface morphology, and NMR spectra. Integrated 16S rRNA sequencing and untargeted metabolomics suggested that GP-1 selectively enriched beneficial bacteria, including Bifidobacterium, Mitsuokella , and Megamonas , and promoted the accumulation of health-associated metabolites (particularly short-chain fatty acids). Functionally, fermentation products of GP-1 markedly alleviated inflammation in lipopolysaccharide-stimulated RAW264.7 macrophages by reducing pro-inflammatory cytokine production and suppressing NF-κB signaling. Collectively, GP-1 acted as a microbiota-utilizable prebiotic with potent anti-inflammatory effects, demonstrating its potential as a functional ingredient for gut health modulation.