Immunomodulatory Acidic Polysaccharide from Jujube Fruit (Zizyphus jujuba Mill.): Insight into Their Chemical Characteristics and Modes of Action

Jujube (Zizyphus jujuba Mill.) has been consumed globally as a fruit and a nutraceutical food for millennia. This study presents the isolation and purification of a novel water-soluble polysaccharide fraction, ZJMP-2, from Z. jujuba Mill. ZJMP-2 underwent characterization through Fourier transform infrared (FT-IR), high-performance gel permeation chromatography-laser light scattering (HPGPC-LLS), gas chromatography-mass spectrometry (GC-MS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and nuclear magnetic resonance (NMR) analyses. It consists of glucose, galactose, arabinose, rhamnose, and galacturonic acid in molar ratios of 0.41:0.08:0.11:0.05:0.33 and boasts an average molecular weight of approximately 57.8 kDa. Its backbone features the structure →2)-α-l-Rhap-(1 → 4)-α-d-GalpA-(1 → 4)-α-d-GalpA-6OMe-(1 → 4)-α-d-GalpA-(1 → 3, 4)-α-d-Glcp-(1 →, with branching at →5)-α-l-Araf-(1 →, →4)-β-d-Galp-(1 →, and →4)-α-d-Glcp-(1→ at position O-3 of →3, 4)-α-d-Glcp-(1 →. These structural variations contribute to the pronounced immunoregulatory effects of ZJMP-2. Specifically, ZJMP-2 significantly elevated the expression levels of TLR4, NF-κB, and TRAF6 proteins, enhancing RAW264.7 cell activity, index of splenic lymphocytes, and the production of cytokines and NO, thereby activating macrophages and promoting lymphocyte proliferation. In vivo studies demonstrated that ZJMP-2 promoted the heart, spleen, and bone marrow indices, peripheral blood and spleen cell counts, and the number of heart and bone marrow cells in mice. These findings demonstrated that ZJMP-2 has potential as an immunomodulator and provides valuable insights for developing natural immunomodulators in the pharmaceutical industry.