Deep eutectic solvent extraction of polysaccharides from Gastrodiae elata with ultrasonic and enzymes assistance: Process optimization, structure, and antioxidant activity

Gastrodia elata polysaccharides (GEPs) have garnered attention due to their various bioactivities; however, their current extraction yield is low, limiting widespread application. This study employed ultrasonic enzyme-assisted deep eutectic solvent (DES) extraction to enhance efficiency and compared the physicochemical properties, structure, and antioxidant activity of the polysaccharides with those obtained by traditional hot water extraction. Additionally, density functional theory (DFT) was used to explore the DES14 extraction mechanism. Results indicated that the extraction yield from the ultrasonic enzyme-assisted DES14 method (25.22 %) was 3.11 times higher than that of the hot water method (8.11 %), and the molecular weight was 0.21 times. Furthermore, the polysaccharides extracted by this method exhibited superior antioxidant activity, effectively reducing malondialdehyde and reactive oxygen species accumulation, while enhancing antioxidant enzyme activity to combat oxidative stress. Both polysaccharides were α-glucans linked by 4-O-D-Glcp without triple helical structures. DFT analysis demonstrated that the binding energy of DES14 with GEPs was significantly higher than with water, enhancing GEPs solubility through hydrogen bond network formation, thereby notably improving extraction yield. This study provides an efficient method for extracting natural plant polysaccharides and a theoretical basis for GEPs application in the food industry.