Structural elucidation, anti-inflammatory activity and intestinal barrier protection of longan pulp polysaccharide LPIIa

In this study, LPIIa, a purified polysaccharide from longan pulp, was isolated. Its anti-inflammatory activity and intestinal barrier protection were investigated with LPS-treated co-culture model of Caco-2 cells and RAW 264.7 macrophages. The average molecular weight LPIIa was 159.3 kDa. Its detailed structure was shown below. The backbone of LPIIa was composed of (1→3,4)-linked-α-Rhap, (1→4)-linked-β-Galp, (1→6)-linked-β-Galp, and (1→3,6)-linked-β-Galp, with branches at the O-4 of Rha and O-3 of Gal, consisting of side chains of α-Araf, β-Galp, and α-Glcp. In LPS-induced RAW 264.7 macrophages, LPIIa suppressed the production of inflammatory mediators, including TNF-α, IL-6, NO, and PGE2, and inhibited iNOS and COX-2 gene expression. In addition, LPIIa attenuated intestinal tight-junctional channel protein Claudin-2 expression and increased tight-junctional barrier protein ZO-1 expression in Caco-2 cells. Knowing the structural features and activities of longan polysaccharide gives insights into longan polysaccharide application as an anti-inflammatory agent or adjuvant in curing the intestinal inflammation.