Mechanochemical Approach to Obtaining a Multicomponent Fisetin Delivery System Improving Its Solubility and Biological Activity

In this study, binary amorphous solid dispersions (ASDs, fisetin-Eudragit^®) and ternary amorphous solid inclusions (ASIs, fisetin-Eudragit^®-HP-β-cyclodextrin) of fisetin (FIS) were prepared by the mechanochemical method without solvent. The amorphous nature of FIS in ASDs and ASIs was confirmed using XRPD (X-ray powder diffraction). DSC (Differential scanning calorimetry) confirmed full miscibility of multicomponent delivery systems. FT-IR (Fourier-transform infrared analysis) confirmed interactions that stabilize FIS’s amorphous state and identified the functional groups involved. The study culminated in evaluating the impact of amorphization on water solubility and conducting in vitro antioxidant assays: 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)—ABTS, 2,2-diphenyl-1-picrylhydrazyl—DPPH, Cupric Reducing Antioxidant Capacity—CUPRAC, and Ferric Reducing Antioxidant Power—FRAP and in vitro neuroprotective assays: inhibition of acetylcholinesterase—AChE and butyrylcholinesterase—BChE. In addition, molecular docking allowed for the determination of possible bonds and interactions between FIS and the mentioned above enzymes. The best preparation turned out to be ASI_30_EPO (ASD fisetin-Eudragit^® containing 30% FIS in combination with HP-β-cyclodextrin), which showed an improvement in apparent solubility (126.5 ± 0.1 µg∙mL⁻¹) and antioxidant properties (ABTS: IC₅₀ = 10.25 µg∙mL⁻¹, DPPH: IC₅₀ = 27.69 µg∙mL⁻¹, CUPRAC: IC_0.5 = 9.52 µg∙mL⁻¹, FRAP: IC_0.5 = 8.56 µg∙mL⁻¹) and neuroprotective properties (inhibition AChE: 39.91%, and BChE: 42.62%).