Molecular Interactions of Saccharides and Their Derivatives with Thiamine HCl and Pyridoxine HCl Vitamins in Aqueous Solutions: Calorimetric, Viscometric, and NMR Spectroscopic Studies

Abstract

Limiting standard enthalpies of dilution (Δ dil H°) and Jones−Dole viscosity B-coefficients of various polyhydroxy solutes, viz., saccharides, their methyl and deoxy derivatives, and sugar alcohol in 0.05, 0.15, 0.25, and 0.35 mol•kg −1 thiamine HCl (aq) and pyridoxine HCl (aq) solutions have been determined from heat change (q) and viscosity (η) data at T = 288.15−318.15 K and pressure p = 0.1 MPa. The corresponding transfer parameters (Δ tr Δ dil H°, Δ tr B), change in heat capacity (Δ dil C°p ,2,m ), and enthalpic (h AB and h ABB ) and viscometric (η AB and η ABB ) pair and triplet interaction coefficients have also been derived. The dB/dT coefficients have been calculated and discussed in terms of the kosmotropic or chaotropic nature of solutes in aqueous solutions of vitamins. The present results have also been compared with previously reported studies carried out in L-ascorbic acid. 17 Further, NMR spectroscopy has been employed to understand the nature of interactions occurring in ternary solution {polyhydroxy solute + vitamins + 9:1 (w/w) H 2 O−D 2 O} at molality m B = 0.15 mol•kg −1 and T = 300.15 K. The results have been explained in terms of contributions due to hydrophilic−hydrophilic/hydrophobic interactions and H-bonding between solute−solute/cosolute molecules. The effect of stereochemistry and molecular conformations of both polyhydroxy solutes and cosolutes (vitamins) have also been discussed.

Elucidation of Interactions between Ciprofloxacin Hydrochloride Monohydrate and Constituents of Nucleic Acids in Aqueous Solutions at Different Temperatures

“…The enthalpy change is a highly sensitive thermodynamic parameter that indicates whether the solute− solute and solute-cosolute interactions are exothermic or endothermic, whereas the volumetric, acoustic and transport studies deal with the bulk macroscopic properties, so the orders of their transfer values are difficult to compare. Such types of transfer have also been observed for saccharides in the presence of pyridoxine HCl and thiamine HCl, 55 where the orders of Δ tr V 2,Φ 0 and Δ tr B values show different trends than that of Δ tr Δ dil H°values. Positive values of transfer parameters (Δ tr V 2,Φ 0 and Δ tr B) for saccharides in the presence of vitamins have been reported, and the positive values of Δ tr Δ dil H°have also been seen and increase when the molality of both cosolutes increases.…”