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

Jujube (<i>Zizyphus jujuba</i> 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 <i>Z. jujuba</i> 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-Rha<i>p</i>-(1 → 4)-α-d-Gal<i>p</i>A-(1 → 4)-α-d-Gal<i>p</i>A-6OMe-(1 → 4)-α-d-Gal<i>p</i>A-(1 → 3, 4)-α-d-Glc<i>p</i>-(1 →, with branching at →5)-α-l-Ara<i>f</i>-(1 →, →4)-β-d-Gal<i>p</i>-(1 →, and →4)-α-d-Glc<i>p</i>-(1→ at position O-3 of →3, 4)-α-d-Glc<i>p</i>-(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. <i>In vivo</i> 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.