Ultrasound-assisted natural deep eutectic solvent for the extraction of flavonoids from hawk tea: COSMO-RS screening, optimization, and in vitro starch digestion

An ultrasound-assisted natural deep eutectic solvent (UAE–NADES) method was developed to extract hawk tea flavonoids (HTFA). Conductor-like screening model for realistic solvents (COSMO-RS)-guided screening and experimental validation identified betaine–urea as the optimal solvent. Using response surface methodology, we optimized the UAE–NADES system for HTFA, achieving a yield of 832.96 ± 14.72 mg RE/g DW. Mechanistic studies revealed that the UAE–NADES system facilitated extraction via cell wall disruption and hydrogen bonding. HPD600 resin effectively purified the crude extract, with adsorption following pseudo-second-order kinetics, while the recovered NADES retained satisfactory extraction performance over four cycles. Astragalin, isoquercitrin, and hyperoside were the major flavonoids in the purified extract (PFE). During in vitro starch digestion, PFE reduced the estimated glycemic index, increased resistant starch, and inhibited α-amylase (IC 50 = 0.13 mg/mL). This work provides a green extraction and purification strategy for HTFA and demonstrates its effects on α-amylase activity and starch digestion in vitro .