Hydrophobic Deep Eutectic Solvent-Derived Curcuminoids Loaded into a Double-Layer Colloidal Delivery System: Physicochemical Properties and In Vitro Biological Activity.

Hydrophobic deep eutectic solvents (HDESs) have been recognized as effective environmentally friendly extraction media for the recovery of lipophilic bioactive chemicals. Nonetheless, their incorporation with sophisticated delivery systems remains mostly unexamined. This study aimed to develop a curcuminoid-rich powder formulation from turmeric (Curcuma longa L.) and to evaluate its physicochemical properties, antioxidant activity, and effects on cell metabolic activity in vitro. Initially, 30 HDES systems based on thymol or menthol were prepared and compared in terms of their curcuminoid extraction performance. The thymol/lactic acid system (2:1, molar ratio) produced the highest total curcuminoid concentration among the screened HDES systems. The extraction parameters were subsequently optimized using a Box-Behnken response surface design. Under the optimized conditions, the total curcuminoid concentration in the analyzed extract solution was 6692.12 ppm. Then, the obtained extracts were incorporated into a double-layer emulsification system by high-pressure homogenization and converted into encapsulated powder form by spray-drying. The particle distribution index (PDI) of the prepared emulsion system was determined as 0.282, indicating a homogeneous distribution of particles within the emulsion system. The total curcuminoid-based encapsulation efficiency of turmeric powders obtained using a double-layer encapsulation system was determined to be 87.33%. Under separately simulated gastric and intestinal conditions, the detected curcuminoid recovery values were similar, at 31.24% and 31.10%, respectively. The ABTS radical-scavenging activity measured after the simulated intestinal treatment reached 81.57%. However, the possible contribution of residual HDES components to this activity could not be determined. The encapsulated powder caused a concentration-dependent reduction in the metabolic activity of DU-145 prostate cancer and Caco-2 colorectal adenocarcinoma cells in the MTT assay. To conclude, the integrated approach enabled the production of a curcuminoid-rich powder with high encapsulation efficiency. The findings support further investigation of the formulation's technological and biological properties.