Structural characterization and immunomodulatory activity of a new polysaccharide isolated from the radix of Platycodon grandiflorum

Summary In this study, a novel polysaccharide fraction (PGPIV‐1‐a) was isolated from Platycodon grandiflorum through the combination of DEAE‐52 and Sephadex G‐100 chromatography. PGPIV‐1‐a was a neutral heteropolysaccharide with an average molecular weight of about 6462 Da. PGPIV‐1‐a was composed of glucose, arabinose and mannose in the relative molar ratio of 64.79%, 31.16% and 4.05%. The main linkage types in PGPIV‐1‐a consisted of → 6)‐β‐Glcp‐(1 → and →5)‐α‐L‐Ara‐(1→. Bioactivity assay results showed that PGPIV‐1‐a significantly stimulated the proliferation of RAW264.7 cells and enhanced their phagocytic capacity in a dose‐dependent manner. In addition, treatment with higher dosage of PGPIV‐1‐a (800 μg mL −1 ) remarkably induced the secretion of NO, TNF‐α and IL‐6. This study provides a theoretical basis for further systematic investigation and utilisation of Platycodon grandiflorum polysaccharides.