Correlation of conformational changes and immunomodulatory activity of lentinan under different subcritical water temperature

In order to reveal the intrinsic nature of the reduction or disappearance of biological activity in the processing and preparation of polysaccharides, and realize the effective control of highly active polysaccharides, the correlation between conformation and immunomodulatory activity of lentinan under different subcritical water temperatures was investigated. The results showed that, compared with the lentinan extracted by hot water (HW-L), with the increase of temperature (100–160 °C), the molecular weight of lentinans decreased (5.041 × 105–1.754 × 106 g/mol) and the rigidity of the chain weakened. The chains gradually loosened and a rigid-flexible transition occurred. At 160 °C, the conformation of lentinan completely changed from triple helix to random coil. In-vitro cell experiments showed that, lentinan at 120 °C could more efficiently promote the proliferation and phagocytosis of RAW264.7 cells, and significantly promote the secretion of NO, TNF-α, IL-6 and IL-1β, exhibiting stronger immunomodulatory activity. But the activity of lentinan decreased sharply at 150–160 °C. These results suggest a significant correlation between polysaccharide chain conformation and immunomodulatory activity under different subcritical water temperature conditions. By adjusting the temperature of subcritical water, the chain conformation of polysaccharides can be controlled, resulting in more efficient extraction of highly active polysaccharides.