Preparation of Polysaccharides from Liubao Brick Tea and Its Immunomodulatory Activity

Objective: To optimize the extraction process of tea polysaccharides from Liubao brick tea and to further investigate the immunomodulatory effects and the possible regulatory mechanisms. Methods: A single-factor experiment was used to investigate the effects of extraction temperature, material-liquid ratio, and ethanol concentration on the yield of tea polysaccharides, based on which the extraction process was optimized by combining with response surface methodology. By measuring the phagocytosis and nitric oxide (NO) release of Liubao brick tea polysaccharides on RAW264.7 cells, detecting the expression of genes and proteins related to nuclear factor-κB (NF-κB) and AMP-dependent protein kinase (AMPK) signaling pathway, in vitro immunomodulatory activity of the purified tea polysaccharides was evaluated. Results: The optimal extraction process for the polysaccharides from Liubao brick tea were as follows: 91.11 ℃ of the extraction temperature, 1:15.45 of the solid-liquid ratio, and 82.84% of the ethanol concentration. In vitro immunomodulatory activity assay showed that Liubao brick tea polysaccharides significantly enhanced phagocytosis and NO release of RAW264.7 cells, significantly activated NF-κB and AMPK signaling pathway, and significantly up-regulated the mRNA expression levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) to exert immunomodulatory effects. Conclusion: By optimizing the extraction temperature, material-liquid ratio and ethanol concentration, the yield of Liubao brick tea polysaccharide could be effectively improved, and it could play an immunomodulatory role by activating the NF-кB/AMPK pathway. The results provide a research basis for the in-depth investigation and application of the Liubao brick polysaccharide.