Comparison of the chemical composition and antioxidant stress ability of polysaccharides from Auricularia auricula under different drying methods

Auricularia auricula fruiting body-derived polysaccharides (AAPs) were dried using different drying procedures, including hot air-, far infrared-, freeze-, and microwave-drying. The influences of different drying procedures on the chemical compositions and antioxidant activity in vitro and in vivo of AAPs were investigated. The results indicated that freeze-dried AAPs (AAPs-F) possessed the highest uronic acid content (33.53%) and the lowest molecular weight (406.77 kDa). Moreover, AAPs-F exhibited the most potent antioxidant abilities in vitro, including ABTS⁺ and DPPH˙ scavenging abilities, ferric reducing power, and metal ion chelating capacity. Besides, AAPs-F could significantly prolong the lifespan of wild-type C. elegans under oxidative stress induced by H₂O₂ and methyl viologen (p < 0.05) and upregulate the mRNA expression levels of daf-16 (>2.7 fold), sod-3 (>9.2 fold), skn-1 (>4.5 fold) and sir-2.1 (>1.9 fold), and play a significant role in protecting C. elegans against apoptosis (p < 0.05). Hence, freeze-drying was determined as the preferred procedure for obtaining high-quality AAPs.