Structural properties of two glycans in the fruits of jujube and their regulation effect of M1-type and M2-type macrophage.

Two glycans, ZJPr2-2-1 and ZJPr3-2-1, were isolated from jujube fruits. Structural analysis revealed ZJPr2-2-1 (7.20 kDa) as a previously unreported pectin featuring main chain of →4)-α-D-GalpA-(1→, →3,4)-α-D-GalpA-(1→, and →3)-α-L-Rhap-(1→, with side chains containing →4)-α-L-Arap-(1→, and t-4-deoxy-L-threo-hex-4-enopyranuronic acid (t-α-L-HexA), as well as two isolated fragments linked to →4)-β-D-GalpA, →4)-α-D-GalpA. Nevertheless, the absence of HMBC correlations precluded the structural elucidation of its connected side chain. Meanwhile, ZJPr3-2-1 was identified as the first plant-derived cyclic α-1,6-glucan heptasaccharide. Both glycans were found to promote M1 macrophage polarization (increased CD86 and decreased CD206 expression), and enhance the production of pro-inflammatory mediators (NO, iNOS, and TNF-α) in RAW264.7 cells. The mechanism was supposed to associated with the direct (ZJPr3-2-1) and indirect (ZJPr2-2-1) activation of the Dectin-1/Syk signaling pathway.