4-O-Methylglucuronoxylan from Hygrophila Ringens var. Ringens Seeds: Chemical Composition and Anti-Inflammatory Activity

Hygrophila ringens var. ringens is a medicinal plant of the Acanthaceae family. A soluble polysaccharide is extracted from H. ringens seeds using warm water, followed by deproteinization and purification using column chromatography. DL1 is characterized comprehensively using spectroscopic and chromatographic techniques and identified as a polymer containing xylose (Xyl; 78.5%) and 4-O-methyl-d-glucuronic acid (4-O-MeGlcA; 21.5 %). The most prominent glycosidic linkages detected are terminal-xylose (T-Xyl); 1,2,3,4-Xylp; 1,2,4-Xylp; and T-4-O-MeGlcA. DL1 belongs to the xylan group and is a 4-O-methylglucuronoxylan. DL1 exhibits inhibition of bovine serum albumin denaturation with IC50 values of 0.35 mg mL-1 and a similar activity to diclofenac (non-steroidal anti-inflammatory drug). In a model of lipopolysaccharide-stimulated macrophages, DL1 (20-40 mu g mL-1) strongly inhibits inflammatory cytokines and reactive oxygen species release without having significant macrophage cytotoxicity. The inhibitory effect of DL1 on inflammatory cytokines is mediated by the activation of mitogen-activated protein kinases by inhibiting the phosphorylation of p38 and extracellular signal-regulated kinase. These results highlight the potential of DL1 for treating inflammation through its cytokine-suppressive activity.