Anti-inflammatory and gut microbiota regulatory effects of ultrasonic degraded polysaccharides from Auricularia auricula-judae in DSS-induced colitis mice

Auricularia auricula-judae is a widely cultivated mushroom species known for its edible and medicinal properties. Polysaccharides have been the focus of research because of their potential bioactivities; nonetheless, the structural complexity and molecular weight have hindered a complete understanding of their bioactivities. In this study, AP-1 polysaccharide was isolated from A. auricula-judae and subjected to ultrasonic degradation at different time points to improve their anti-inflammatory effects. The results showed that when AP-1 was degraded for 9 min (AP-2) and 20 min (AP-3), the NO inhibition rate was significantly increased in LPS-stimulated RAW 264.7 cells. The structural and physiochemical properties of native and degraded polysaccharides were analyzed, and it was found that the degradation process significantly reduced molecular weight and altered the particle size, viscosity, crystallinity, and helical structure. Furthermore, native and degraded polysaccharides (AP-1, AP-2, and AP-3) anti-inflammatory effects were investigated in the DSS-induced colitis mouse model. Degraded polysaccharides resulted in significant improvements, including recovery from weight loss, reduced disease activity, shortened colon length, and decreased inflammation, while AP-3 showed the most promising effects. Gut microbiota 16S rRNA sequencing revealed that AP-3 potentially increases healthy gut microbiota and inhibits unhealthy gut microbiota. Overall, this study demonstrates that ultrasonic degradation could be a great technique to modify polysaccharides' MW and physiochemical properties to improve anti-inflammatory and gut microbiota regulatory effects.