Experimental and COSMO-RS theoretical exploration of rutin formulations in natural deep eutectic solvents: Solubility, stability, antioxidant activity, and bioaccessibility

The present study aimed to estimate the solubility of rutin in twelve natural deep eutectic solvents (NADES) and to compare experimental results with the theoretical prediction by the COSMO-RS program. The mandatory component in all investigated systems was choline chloride (ChCl), and the variable component was hydrogen bond donor (HBD), including organic acids, sugars, alcohols, and urea. The FRAP method tested the antioxidant activity of rutin formulations in NADES systems. It was found that theoretical prediction and experimentally determined solubilities of rutin were in excellent agreement. The highest solubility of rutin was observed in 1,2-propanediol (ChCl:1,2PD), 59.30 mg/mL and urea-based systems (ChCl:Ur), 57.99 mg/mL. These systems were further investigated, including dissolution efficiency study, stability to UV and hydrogen-peroxide degradation, and bioaccessibility of rutin by in vitro digestion model. It was found that ChCl:Ur protected rutin against UV-induced oxidation. It was also found that rutin solubilization in ChCl:Ur and ChCl:1,2PD retained rutin for 78.64% and 76.57% in digestive fluids after in vitro digestion and enhanced bioaccessibility compared to the control for more than 60%.