Purification and Identification of a Multidomain Pectin from <i>Phyllanthus emblica</i> L.: Structure–Activity Relationship Analysis on Glycolipid-Lowering Activity via Gut Action Targets

Natural functional hydrophilic colloids with glycolipid-modulating activities demonstrated tremendous developmental potential. Establishing precise structure–activity relationships requires highly purified and structurally defined pectin. A novel multidomain pectin (P1) was successfully purified from P. emblica through integrated yeast fermentation, XAD-16 macroporous resin treatment, and ultrafiltration. Structure–activity analysis demonstrated that RG-I domain proportion/side chain type and molecular conformation (depolymerization and aggregation) of polysaccharide exerted comprehensive effects on the upper gastrointestinal glycolipid regulation. In addition, multidomain pectin with a stable structure could show greater proliferative ability of mixed probiotics related to glycolipid metabolism. Molecular simulations identified the RG-I domain as the primary bioactive region. Arabinan side chains mediated starch binding via van der Waals and hydrogen bonding interactions, while galactan components facilitated bile acid and cholesterol complexation through van der Waals interactions. This study delineated the multitarget mechanistic principles underlying P1’s modulation of glycolipid metabolism disorders, providing molecular insights for pectin polysaccharide structure–function studies.