α-Glucosidase inhibitory activities of natural deep eutectic systems and their components: Ascorbate is a powerful inhibitor of α-glucosidase

Natural Deep Eutectic Solvents (NADES) have become increasingly popular in food chemistry as novel green solvents. This work aimed to explore α-glucosidase inhibitory activities of twelve choline chloride (ChCl) based NADES systems and their components. Hydrogen Bond Donors (HBD) used in the systems were selected organic acids, sugars, alcohols, and urea. The lowest inhibiting potential showed systems that contained alcohol and urea. It was found that both components in NADES systems contributed to α-glucosidase inhibition. The highest inhibiting potential showed ascorbate and fructose-based systems because of the presence of ascorbate (IC50 = 1.8·10−4 mg/mL) and fructose (IC50 = 0.2 mg/mL) as the most potent inhibitors. Both ascorbate and fructose showed reversible and non-competitive α-glucosidase enzyme inhibition. Compared to the drug acarbose, it was determined that the IC50 value for ascorbate was about 182 times lower and the inhibition constant (KI) was 64 times lower. The binding energy for ascorbate was −5.9 kcal/mol.