Preparation, structural characterization, and immunomodulatory activity of Eucommia ulmoides polysaccharides
Cerasus humilis (Bge.) Sok It is a deciduous shrub belonging to the Rosaceae cherry genus, mainly distributed in provinces and regions such as Heilongjiang, Jilin, and Liaoning. It is a pioneer tree species for afforestation in the arid areas of Northwest China and a unique fruit tree in China. The fruit of Eucommia ulmoides is bright red and full, with a special aroma and high calcium content. It is known as the “calcium fruit” and is a natural source of calcium and a health fruit. It is also one of the “third-generation functional fruits”. Eucommia ulmoides fruit is rich in various sugars, organic acids, amino acids, vitamins, and mineral elements, making it a fruit with high nutritional value. Eucommia ulmoides is a traditional Chinese medicine material with medicinal and edible properties. Polysaccharides are a type of macromolecular polymer with various pharmacological activities such as immune regulation, anti-tumor, anti-cancer, antibacterial, and antioxidant properties. In recent years, products developed through deep processing of Eucommia ulmoides fruit include Eucommia ulmoides fruit juice, dried fruits, fruit wine, etc. However, there are few reports on the research of Eucommia ulmoides polysaccharides. This article focuses on the preparation of polysaccharides, structural characteristics, and immune regulatory activity of Eucommia ulmoides cultivated in the sandy land of Yulin, Shaanxi Province. The aim is to provide theoretical basis and technical support for the development and utilization of Eucommia ulmoides resources in China.

Macrophages are important carriers for evaluating the immune regulatory function of bioactive components. Macrophages exert their immune function by secreting various cytokines such as nitric oxide (NO), tumor necrosis factor – α (TNF – α), interleukin-6 (IL-6), interferon – β (IFN – β), interleukin-1 (IL-1), etc. Plant polysaccharides regulate the immune function of macrophages by modulating the secretion of cytokines. NO, as an important signaling molecule, mediates various biological functions within cells and helps to kill tumor cells and pathogenic microorganisms. TNF – α can be produced by activated macrophages and can directly participate in maintaining immune homeostasis, including inflammation, differentiation, lipid metabolism, and apoptosis. Research has shown that IL-6 can be secreted by various cells and is considered the most important immune regulatory mediator associated with fever during the induction of acute phase protein responses. IFN – β participates in antiviral immunity, reduces T cell proliferation, induces dendritic cell growth, maturation, and activation, and inhibits B cell and T cell apoptosis. These cytokines are mainly small molecule proteins secreted by immune cells, which play important roles in the body’s immune and inflammatory responses. Yao et al. found that mung bean polysaccharides significantly increased the release of NO, TNF – α, and IL-6 in macrophages. Du et al. found that fig polysaccharides can significantly promote the secretion of cytotoxic molecules (NO) and cytokines (TNF – α and IL-6), as well as the phagocytic activity of RAW264.7 macrophages. Ren et al. studied the effect of Artemisia annua seed polysaccharides on RAW 264.7 cells and found that Artemisia annua seed polysaccharides can significantly promote the secretion of NO, TNF – α, IL-6, and IFN – β in RAW 264.7 cells. This is consistent with the results obtained in this experiment that Eucommia ulmoides polysaccharides can significantly promote the release of NO, TNF – α, IL-6, and IFN – β cytokines in RAW 264.7 cells, indicating that Eucommia ulmoides polysaccharides have immunomodulatory activity.

The water extraction and alcohol precipitation method was used to extract polysaccharides from Eucommia ulmoides, and the optimal extraction process conditions were obtained as follows: extraction temperature of 79 ℃, extraction time of 2 hours, liquid to material ratio of 16:1 (mL/g), and the yield of polysaccharides from Eucommia ulmoides dry powder was (32.18 ± 0.08)%. The polysaccharide content in CHPP-1 and CHPP-2 is 99.16% and 99.33%, respectively. The main monosaccharide composition and molar ratio of CHPP-1 are arabinose: galacturonic acid: galactose=51.4:29:17.36, with a molecular weight of 47.26 kDa. The main monosaccharide composition and molar ratio of CHPP-2 are arabinose: galacturonic acid: galactose=41.81:28.24:11.68, with a molecular weight of 22.94 kDa. Europa polysaccharide is a pyran ring polysaccharide. CHPP-2 can activate macrophages within the concentration range of 20-640 μ g/mL, significantly promoting the release of NO, TNF – α, IL6, and IFN – β cytokines in a dose-dependent manner, indicating that polysaccharides from Eucommia ulmoides have certain immunomodulatory activity.