Structural Characterization and In Vitro Anti-Inflammatory Activity of Polysaccharides Isolated from the Fruits of Rosa laevigata

RLPa-2 (Mw 15.6 kDa) is a polysaccharide isolated from Rosa laevigata Michx. It consists of arabinose (Ara), galactose (Gal), rhamnose (Rha), glucose (Glc), xylose (Xyl), and galacturonic acid (Gal-UA) with a molar ratio of 1.00:0.91:0.39:0.34:0.25:0.20. Structural characterization was performed by methylation and NMR analysis, which indicated that RLPa-2 might comprise -> 6)-alpha-D-Galp-(1 ->, -> 4)-alpha-D-GalpA-(1 ->, alpha-L-Araf-(1 ->, -> 2,4)-alpha-D-Glcp-(1 ->, beta-D-Xylp, and alpha-L-Rhap. In addition, the bioactivity of RLPa-2 was assessed through an in vitro macrophage polarization assay. Compared to positive controls, there was a significant decrease in the expression of M1 macrophage markers (CD80, CD86) and p-STAT3/STAT3 protein. Additionally, there was a down-regulation in the production of pro-inflammatory mediators (NO, IL-6, TNF-alpha), indicating that M1 macrophage polarization induced with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) stimulation could be inhibited by RLPa-2. These findings demonstrate that the RLPa-2 might be considered as a potential anti-inflammatory drug to reduce inflammation.