A galactoglucan from calcium chloride-stimulated Lactiplantibacillus plantarum ZGS521: Structural characterization, antioxidant and anti-inflammatory properties.

A homogeneous galactoglucan (C-LPE3), an exopolysaccharide produced by CaCl2-stimulated Lactiplantibacillus plantarum ZGS521, was purified. The structural features, antioxidant and anti-inflammatory capacities of C-LPE3 were evaluated. The molecular weight of C-LPE3 was determined as 20.48 kDa. The main chain of C-LPE3 was composed of →6)-α-d-Glcp-(1 → 6)-α-d-Galp-(1 → residues, with side chains including α-d-Glcp-(1 → at the O-3 position of →3,6)-α-d-Glcp-(1 → and α-d-Galp-(1 → 4)-α-d-Galp-(1 → at the O-4 position of →4,6)-α-d-Galp-(1→. SEM analysis indicated that C-LPE3 exhibited an amorphous structure and flaky morphology. C-LPE3 demonstrated potent free radical scavenging property. In H2O2-treated RAW264.7 macrophages, it exerted protective effects by decreasing MDA and ROS contents while enhancing SOD and CAT activities. In LPS-treated macrophages, C-LPE3 suppressed phagocytosis and NO production, modulated cytokine secretion, and activated the AMPK pathway while inhibiting mTOR and NF-κB pathways. The inhibitory effects on mTOR and NF-κB signaling were likely mediated by AMPK activation. These findings deepen understanding of the structure-bioactivity relationship of EPS from L. plantarum and suggest the potential of C-LPE3 as a natural antioxidant and anti-inflammatory agent, deserving further investigation on its application in foods and pharmaceuticals.