Polysaccharides from Auricularia cornea var. Li.: Structural alterations during in vitro digestion and its potent immunomodulatory properties on macrophages

Auricularia cornea var. Li, a fungus known for its medicinal and edible properties in China, exhibits immunomodulatory effects through its polysaccharides. This research investigated the structural characteristics and immunomodulatory properties of Auricularia cornea var. Li. polysaccharide (ACP) and its digested form (d-ACP). The results showed that both ACP and d-ACP contained a high content of total sugar (82.21% and 74.17%) and glucose (52.46 and 86.42 mol%). Meanwhile, chemical composition analysis indicates the structural changes that occurred in ACP during in vitro digestion, including a reduction in the molecular weight and monosaccharide viability, suggesting its susceptibility to digestive processes. Furthermore, the immunomodulatory activities of ACP and d-ACP on RAW 264.7 macrophages were explored. Both ACP and d-ACP were found to promote macrophage proliferation, alter cell morphology, enhance phagocytic ability, and stimulate the production of pro-inflammatory cytokines such as NO, IL-6, IL-1β, and TNF-α, demonstrating their potent immunomodulatory potential. Specially, TLR4 and MR receptors are highlighted to be integral to the immunomodulatory effects of ACP and d-ACP. Our findings shed light on the structural alterations during digestion and the immunomodulatory properties of ACP and d-ACP, providing valuable insights into the potential applications of ACP in the field of immunomodulation and functional foods.