Purification, structural analysis, and hypoglycemic activity of Auricularia auricula-judae polysaccharides extracted with natural deep eutectic solvents

The in vitro research found that Auricularia auricula-judae (A. auricula) crude polysaccharides showed hypoglycemic and antioxidant properties, whereas purified polysaccharides were more effective. A. auricula polysaccharide was identified as a typical heteropolysaccharide, with a pyran-type sugar ring coupled via α- and β-type glycosidic linkage. The monosaccharide composition includes Man, Xyl, Ara, Glc, Rha, and galactose (Gal), at a molar ratio of 61.36:37.92:36.27:25.79:24.30:20.38, while also containing a small amount of galacturonic and glucuronic acid. A. auricula polysaccharide showed smooth, flaky structures, with a small portion exhibiting a filamentous and spherical morphology. A. auricula polysaccharides activate glycogen synthetase kinase 3β (GSK3β) phosphorylation, leading to increased hepatic glycogen production, and they reduce glucose synthesis and lower blood sugar levels by decreasing phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) enzyme activity, and enhancing FOXO1 phosphorylation. The findings suggested that A. auricula polysaccharides could be used as natural hypoglycemic agents.