Effects of Ultrasound-Assisted Deep Eutectic Solvents Method on the Physicochemical Characteristics and Biological Activity of Polysaccharide from Highland Barley Distiller's Grains

A green and efficient ultrasound-assisted deep eutectic solvent (UDE) method was developed for the first time to extract beta-glucan-rich polysaccharides from highland barley distiller's grains (HBDG), a major by-product of Baijiu production. Under optimized conditions (choline chloride:lactic acid at a 1:4 M ratio, water content 49%, solid-to-liquid ratio 1:33 g/mL, 79 degrees C, 120 min), the beta-glucan extraction rate reached 55.78%. Systematic comparison with the polysaccharides obtained by hot water extraction (HWE-G) and ultrasound-assisted extraction (UAE-G) revealed that the polysaccharide prepared by UDE extraction (UDE-G) exhibited the lowest molecular weight (68.1 kDa) and viscosity (0.97 mPa & centerdot;s), which correlated with superior antioxidant (ROS scavenging in Raw264.7 cells) and hypoglycemic (alpha-amylase/alpha-glucosidase inhibition, and glucose dialysis retardation index) activities. Notably, UDE-G contained the highest beta-glucan content (83.65%), whereas HWE-G and UAE-G contained only 20.89% and 19.11%, respectively. Mechanistically, the enhanced bioactivity of UDE-G is attributed to its lower molecular weight (68.1 vs. 110.8 kDa for HWE-G), higher glucose molar ratio (82.41% vs. 19.50% for HWE-G), and the retention of its essential beta-glucan structural features, which collectively facilitate better cellular uptake and radical neutralization. This study positions UDE as a green and efficient extraction strategy for valorizing HBDG and highlights UDE-G as a promising functional ingredient for managing hyperglycemia and oxidative stress.