Physicochemical and computational investigations of some essential amino acids prevailing in aqueous solutions of a food preservative (SBz) with the manifestation of hydrophobic and hydrophilic interactions at different temperatures

Abstract

This current research focuses on the physicochemical and computational studies of L-Isoleucine (L-Ilu) and L-Threonine (L-Thr) within varying concentrations (0.001, 0.003, and 0.005 mol.kg−1) of the aqueous solution of Sodium Benzoate (SBz) at five distinct temperatures (293.15, 298.15, 303.15, 308.15, and 313.15 K) and at standard atmospheric pressure. The research involved evaluating volume-related attributes, such as the apparent molar volume (ϕv), limiting partial molar volume (ϕv0), limiting partial molar volume of transfer (Δϕv0), and hydration numbers (nH), through the analysis of density data. Likewise, viscosity assessments were conducted using the Jones-Dole equation and transition state treatment to determine the viscosity B coefficient. Surface tension and conductometric analysis were also conducted. The co-sphere overlap model was employed to investigate interactions among solute molecules and between solute and solvent molecules. Experimental values for Hepler’s constant (∂ϕE0/∂T) and the B coefficient derivatives (dB/dT) indicate the ability of L-Ilu and L-Thr to disrupt the structure in the SBz aqueous solution. The fluorescence spectra of amino acids were measured with varying concentrations of both L-Ilu and L-Thr, and the association constant was then computed. The outcomes from 1H NMR spectroscopy revealed notable shifts in the aromatic protons of Sodium Benzoate and the protons within amino acids (AAs). These shifts suggest a robust interaction, specifically a hydrophobic-hydrophobic interaction between them, a finding consistent with our theoretical observations. The primary goal of this research is to understand the interaction between essential amino acids in the aqueous solution of food preservative that is biologically active. The result of this study could be very beneficial to the pharmaceutical industry.