Low molecular weight polysaccharide of Tremella fuciformis exhibits stronger antioxidant and immunomodulatory activities than high molecular weight polysaccharide.

Low molecular weight polysaccharides had higher bio-activity and bioavailability compared to ultra-high molecular weight polysaccharides, this study aimed to obtain low molecular weight polysaccharides from Tremella fuciformis (TFLP) by using high-temperature and high-pressure assisted hydrochloric acid method to degrade Tremella fuciformis polysaccharides (TFP), and the structural characteristics, in vivo antioxidant and immune enhancing activities of TFP and TFLP was explored through Caenorhabditis elegans (C. elegans) and mice model. It was found that TFP and TFLP were acidic polysaccharides with molecular weights of 2238 kDa and 3 kDa, respectively. The glycosidic bonding of TFP and TFLP was mainly composed of different configurations of mannopyranose. TFP and TFLP had excellent in vivo antioxidant activity and stress resistance by regulating the mRNA transcription level and metabolites in C. elegans. Results also showed that TFP and TFLP could enhance the antioxidant capacity and immunity of serum, spleen and small intestine tissues in normal mice and cyclophosphamide-induced immunosuppressive mice through regulating the relative transcription and expression levels of anti-inflammatory related signaling factors, and it has found that TFLP showed better immune enhancement and antioxidant activity than TFP. In addition, Akkermansia, Bacteroides and Alloprevotella were characteristic bacteria at the genus level in immunosuppressed mice intervened with TFLP, with a significant increase in relative abundance. The content of SCFAs significantly increased in immunosuppressed mice by TFLP. These results indicated that TFP and TFLP had potential in vivo antioxidant and immune enhancing activities.