A polysaccharide isolated and purified from Platycladus orientalis (L.) Franco leaves, characterization, bioactivity and its regulation on macrophage polarization

[Display omitted] •POP2 with immunomudulatory activity was obtained from P. orientalis (L.) Franco.•Structure of POP2 is characterized by methylation, FT-IR and NMR.•POP2 showed bidirectional regulation effects on RAW264.7 cells.•POP2 might regulate macrophages polarization via PI3K and JAK related signal pathway. The structure and bioactivity of a novel polysaccharide from Platycladus orientalis (L.) Franco leaves (POP2) were investigated in the present study. Structure characterization demonstrated that the average molecular weight of POP2 was 9.69 kDa and consisted of arabinose (14.39%), mannose (10.24%), glucose (63.95%) and galactose (11.42%). The main linkage types of POP2 consisted of (1→4)-linked α-d-Glc and (1→6)-linked α-d-Glc based on methylation and NMR analysis. Bioactivity evaluation showed that POP2 could effectively promote the secretion of inflammatory cytokines (IL-6 and TNF-α), as well as the anti-inflammatory cytokines (IL-10) in LPS-induced cells. Besides, the secretion of NO was significantly inhibited by POP2 in M1 model. POP2 could enhance the level of inflammatory cytokines (NO, IL-6 and TNF-α), while the secretion of the anti-inflammatory cytokine TGF-β was markedly suppressed in IL-4 induced cells. Our work attempted to elucidate the regulation of macrophage polarization and support the potential application of POP2 as bioactive ingredient for functional foods.