In Vitro Antidiabetic Activity of Phenolic Compounds from NADES-Extracted SunGold Kiwifruit and Their Fortification in Yoghurt

Type 2 diabetes mellitus (T2DM) is a major global health challenge, which has increased interest in functional foods containing bioactive compounds with antidiabetic potential. This study evaluated the in vitro antidiabetic activity of phenolic compounds extracted from SunGold kiwifruit using a choline chloride–glycerol natural deep eutectic solvent (NADES) and their application in yoghurt. NADES and water extracts were assessed for α-glucosidase and α-amylase inhibition and glucose diffusion retardation. The extracts were incorporated into yoghurt at different concentrations before or after fermentation, followed by assessment of enzyme-inhibitory activities and phenolic profiles. The NADES extract showed stronger α-glucosidase and α-amylase inhibition than the water extract, with IC50 values of 15.331 ± 0.393 and 116.530 ± 2.110 mg/mL, respectively. It also produced greater glucose diffusion retardation at 180 min (62.84%) than the water extract (37.89%). Fortification enhanced enzyme-inhibitory activities in a concentration-dependent manner, with post-fermentation yoghurt containing 30% NADES extract showing the highest α-glucosidase and α-amylase inhibitory activities of 3.615 ± 0.032 mg QE/g and 111.186 ± 0.541 mg AE/g, respectively. LC-MS/MS identified catechin, epicatechin, epigallocatechin, chlorogenic acid, caffeic acid, and gallic acid. These findings demonstrate that the NADES preparation showed greater in vitro carbohydrate-digestive enzyme inhibition and glucose diffusion retardation than the water extract under the tested conditions.