Antioxidant and immunomodulatory activities and structural characterization of polysaccharides isolated from Lobelia chinensis Lour

Background and Objective: Lobelia chinensis Lour is an important anticancer herb used in traditional Chinese medicine. Many botanical polysaccharides are known to exhibit immunomodulatory and anticancer activities. This research aimed to analyze the L. chinensis polysaccharides (LCPs) for their biological activities relevant to their anticancer function. Materials and Methods: Water-soluble LCPs were extracted and purified using size-exclusion chromatography to obtain two dominant polysaccharides, LCP-1 and LCP-2 having molecular masses of 1899 kDa and 5.3 kDa, respectively. The antioxidant potentials of the isolated polysaccharides were evaluated by measuring radical scavenging activities against DPPHC (2,2-diphenyl-1-picrylhydrazyl radical), ABTSC+(2,2'-azino-bis(3-ethylbenzothiazoline6-sulphonic acid radical) and OHC (hydroxyl radical). Immunostimulatory activities of LCP-1 and LCP-2 were measured using mouse macrophages. Structure of the most active fraction (LCP-2) was determined using FT-IR and NMR spectroscopic techniques. Results: Two isolated polysaccharide fractions displayed significant antioxidant activities and stimulated the production of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), although LCP-2 is more effective. Detailed structural characterization by FT-IR and NMR was undertaken for the most active fraction (LCP-2) and confirmed that LCP-2 is(2,1)-β-fructan. Conclusion: The results suggested that the polysaccharides isolated from Lobelia chinensis Lour are potential candidates for immune-chemotherapy and suitable for the treatment of cancer.