Structural characteristics and immunomodulation activity of a polysaccharide from purslane (Portulaca oleracea)

This study aimed to explore the basic structural features and adjuvant activity of polysaccharides from Portulaca oleracea (POP), which were prepared using DEAE Sephadex A50 and Sephadex G 100 column chromatography. Its molecular structures were systematically characterized using multi-chemical and spectroscopic methods including colorimetry, HPGPC-RID, HPLC, GC–MS, methylation, FT-IR, and NMR. In this study, the adjuvant effects of POP were evaluated using ovalbumin (OVA) in mice. And the activation of POP on RAW264.7 cell was also investigated. And the result showed that the molecular weight of POP was 8795 Da. And POP was consisted of Man, GlcN, Glc, Gal, and Ara in the molar ratio of 4.94:0.56:20.55:45.47:27.61. POP exerted immunopotentiation activity in vitro and in vivo. POP significantly activated RAW264.7 cells by promoting the production and mRNA expression of cytokines in vitro. Besides, POP significantly induced the phosphorylation of ERK and NF-κB p65 in RAW264.7 cells, which indicated that POP activated macrophage via ERK and NF-κB signaling pathways. POP not only dramatically boosted the OVA-specific IgG antibody and its isotype titers, but triggered Th1- and Th2- cytokines secretion from splenocytes in immunized mice in vivo. In conclusion, POP exhibited strong immune-enhancing activity in vivo and in vitro.