Study of fluconazole drug behavior in deep eutectic solvents: thermodynamic properties, solubility measurement, and fluorescence spectroscopy

Fluconazole is a crucial antifungal medication with a broad spectrum of activity against various fungal infections. This study thermodynamic properties, solubility measurements and spectrofluorometric method were used for investigating the interactions between fluconazole (FCZ) and deep eutectic solvents (DESs). Five choline chloride-based deep eutectic solvents (DESs) were synthesized. Each DES was prepared by combining choline chloride (a hydrogen bond acceptor, HBA) with a different hydrogen bond donor (HBD): oxalic acid (OX), malonic acid (MA), ethylene glycol (EG), glycerol (G), or urea (U). Subsequently, the interactions between fluconazole (FCZ) and these synthesized DESs were investigated using fluorescence spectroscopy at a temperature of 298.15 K. Fluorescence spectroscopy revealed a strong interaction between fluconazole (FCZ) and deep eutectic solvents (DESs). This was evident from the significant quenching of FCZ's intrinsic fluorescence upon DES addition. The association constant and binding sites were determined. Among the tested DESs, the choline chloride-oxalic acid mixture exhibited the strongest interaction with FCZ. Furthermore, the solubility of FCZ in DES-water mixtures studied at a temperature range of (298.15 to 313.15) K was found to increase with increasing DES concentration. The solubility data were accurately fitted using the e-NRTL and Wilson thermodynamic models. To gain deeper insights, conductor-like screening model (COSMO) calculations were performed on the studied systems. The obtained surface cavity volume and dielectric solvation energy provide valuable information about the intermolecular interactions. Finally, thermodynamic analysis using Gibbs and van't Hoff equations indicated that the dissolution of FCZ in these systems is an endothermic process.