Chemical/color stability and rheological properties of cyanidin-3-glucoside in deep eutectic solvents as a gateway to design task-specific bioactive compounds

The present work attempts to study chemical (related with thermal behavior)/color stability and rheological properties of a model anthocyanin monoglucoside (cyanidin-3-glucoside (c3yglc)) dissolved in nonaqueous deep eutectic systems. Solutions were prepared by dissolving c3yglc in binary and ternary choline chloride (ChCl)-based deep eutectic solvents (BESs and TDESs). Then, they were characterized with respect to viscosity, refractive index, calorimetric (thermogravimetry, differential scanning calorimetry), and spectroscopic (UV-visible (UV-vis) and Fourier transform infrared (FTIR)) properties. FTIR analysis showed no interaction between c3yglc and the selected eutectic solvents, while the thermodynamic studies demonstrated that a chemical interaction may occur instead of a simple physical mixture. Generally, the c3yglc-BDES solutions showed lower viscosities than their corresponding BDESs (ChCl-ethylene glycol, ChCl-urea, and ChCl-glycerol) and TDESs (ChCl-urea/ethylene glycol, ChCl-urea/glycerol, and ChCl-glycerol/ethylene glycol) solvents. The refractive index values ranged between 1.47 and 1.50 for all the studied systems. Chemical and color stability of c3yglc in deep eutectic solvents containing glycerol in their composition were improved by deceleration of their thermal decomposition and maintained color stability when compared with the cy3glc-DES systems containing urea. The results are novel and underline the potential application of green solvents to anthocyanin stability for the improvement of chemical and color protection, which could contribute to the quality of food products, opening new windows for designing bioactive compounds to be potentially applied in different health and food areas.