Interactions of amino acids and peptides with the drug pentoxifylline in aqueous solution at various temperatures: A volumetric approach

Pentoxifylline is used to improve blood flows through peripheral blood vessels. The density of three amino acids and two peptides (glycine, l-alanine, l-valine, glycylglycine, and glycylglycylglycine) are measured using DSA 5000 instrument at T = (293.15, 298.15, 303.15, and 308.15) K in aqueous solution of this compound. The apparent molar volume, (Vϕ), partial molar volume, (Vϕ0), transfer partial molar volume, (ΔVϕ0), and partial molar expansibility, (E20), thermal expansion coefficient, (α2), and Hepler’s constant, (∂2Vϕ0/∂T)2 are calculated from the density data. The above parameters are used to interpret the solute–solute and solute–solvent interactions of amino acids/peptides in aqueous pentoxifylline solution. The dependence of these parameters upon concentration and temperature clearly suggest the role of amino acids/peptides and pentoxifylline in solute–solvent interactions.

► In this study we measured the density ρ, of different amino acids and peptides in aqueous drug solutions.
► Various parameters, viz., Vϕ, Vϕ0, ΔVϕ0, and E20 have been calculated.
► Their exits strong solute–solvent interactions.
► Solute–solvent interactions increase with the increase in the temperature.
► Hydrophobic–hydrophobic interactions increase with the side chain of amino acids.