Physicochemical properties characterizing interactions of streptomycin and neomycin with glucose, sucrose and NaCl in aqueous solution: Biophysical insights

Abstract

In this study we investigated intermolecular interactions of drugs streptomycin and neomycin in the aqueous solution, glucose, sucrose and NaCl to understand the effect of different types of co-solute on the medication. Physicochemical characterization in terms of thermodynamic signatures help in understanding interaction mode of the drug with co-solute molecules. In order to estimate the physicochemical properties we have used ITC (Isothermal Titration Calorimeter), densimeter and UV–visible spectrophotometer techniques. The apparent molar properties of volume and adiabatic compression were found decrease with rise in molality of the drug and increase with rise in temperature. The standard partial molar quantities on volume (V2,m0) and adiabatic compression (Ks,2,m0) of streptomycin were found to be more than that of neomycin in aqueous and mixed aqueous solution. The standard partial molar quantities of transfer for volume (ΔtrV2,m0) and adiabatic compression (ΔtrKs,2,m0) of drug from water to mixed aqueous solutions were found to be positive which suggests ion-ion, ion-hydrophilic or hydrophilic-hydrophilic group interactions dominant over ion-hydrophobic and hydrophobic-hydrophobic group interactions. The exothermic heat supports occurrence of such type of interactions. Absorption maxima and absorbance values were higher in case of aqueous streptomycin than neomycin as former drug was in its dimeric form which suggests the significance of π conjugated system. The values of ΔtrV02,m, ΔtrK0s,2,m and ΔtrHm0 for streptomycin in the presence of aqueous co-solutes were found to be higher than that of neomycin. Partial molar expansion (E20) and expansivity coefficient (α2) values were found to be lesser in case of aqueous streptomycin than that of neomycin.