Preparation, Structural Characterization, and Biological Activities of Selenized Tremella aurantialba Polysaccharides

To investigate the structural characteristics and biological activity differences between Tremella aurantialba polysaccharides (TAP) and selenized Tremella aurantialba polysaccharides (Se-TAP), TAP was prepared using liquid fermentation technology and purified through ethanol precipitation, Sevage deproteinization, and membrane separation. Se-TAP was synthesized by reacting TAP with sodium selenite and nitric acid at 80 ℃ for 7 h. Structural characterization results indicated that both TAP and Se-TAP were primarily composed of glucose and mannose, featuring a β-type glycosidic linkage and a triple-helix structure. Characteristic absorption peaks for Se-TAP were observed in the infrared spectrum at 850 cm^-1and 750 cm^-1, confirming the successful introduction of selenite ester groups (Se＝O and C—O—Se), with a measured selenium content of 533.44 μg/g. Due to acid hydrolysis in the reaction system, Se-TAP underwent side-chain trimming, with the weight-average molecular weight decreasing from 4.62×10⁶ Da (TAP) to 3.94×10⁶ Da, and the PDI decreasing from 2.22 to 2.03, indicating a more uniform molecular weight distribution. In vitro bioactivity assays demonstrated that Se-TAP exhibited significantly enhanced antioxidant capacity compared to TAP, with improved scavenging rates against DPPH, ABTS⁺, and hydroxyl radicals, as well as increased total reducing power. In terms of antitumor activity, Se-TAP showed dose-dependent inhibitory effects on gastric cancer (HGC-27), cholangiocarcinoma (RBE), and pancreatic cancer (PANC-1) cells. Notably, against HGC-27 cells, Se-TAP achieved an IC₅₀ value of 652.95 μg/mL and an inhibition rate of 58.60% at a concentration of 1000 μg/mL, outperforming the positive control 5-fluorouracil. Fluorescence staining confirmed that its mechanism involved inducing cancer cell apoptosis. The findings indicated that selenization modification retained the backbone structure of TAP while significantly enhanced their antioxidant and antitumor activities through structural optimization. This study aimed to provide a theoretical reference for expanding the application of TAP and Se-TAP in the functional food sector.