Solvent effects, solvation, and thermodynamic properties of moxidectin in methyl alcohol, ethyl alcohol, and isopropyl alcohol + water solutions at various temperatures

Using the KAT-LSER model, the solubility of moxidectin (Mox) was studied in methanol (MeOH) – water, ethanol (EtOH) – water, and 2-propanol (2-PrOH) – water mixtures. Solubility was primarily influenced by hydrogen-bond acidity (α), solvent polarity, and cavity effects. The inverse Kirkwood-Buff integrals (IKBI) method was used to calculate the preferential solvation parameter (δx1,Mox). In methanol – water and ethanol – water systems, δx1,Mox values were positive in water-rich regions but negative in alcohol-rich regions from 293.15 to 323.15 K. In 2-PrOH – water mixtures, δx1,Moxremained negative in water-rich areas above 293.15 K. However, all δx1,Moxvalues were below 1 × 10⁻², suggesting negligible preferential solvation. Mox showed improved solubility when the alcohol mole fraction exceeded 0.40 (MeOH), 0.35 (EtOH), and 0.25 (2-PrOH). Thermodynamic analysis revealed that solubility variations are primarily enthalpy-driven. These findings enhance understanding of Mox dissolution behaviour, aiding in the optimisation of formulations for pharmaceutical and personal care applications.