ABSTRACT
ABSTRACT The interaction between 6-shogaol, a pharmacologically active ginger constituent, and human serum albumin (HSA), the main in vivo drug transporter, was investigated using isothermal titration calorimetry (ITC). The value of the binding constant, Ka (5.02 ± 1.37 × 104 M−1) obtained for the 6-shogaol-HSA system suggested intermediate affinity. Analysis of the ITC data revealed feasibility of the binding reaction due to favorable enthalpy and entropy changes. The values of the thermodynamic parameters suggested involvement of van der Waals forces, hydrogen bonds and hydrophobic interactions in the 6-shogaol-HSA complex formation.
Subject(s)
Thermodynamics , Ginger/anatomy & histology , Biological Products/pharmacokinetics , Calorimetry , Serum Albumin/analysisABSTRACT
The interaction of erythrosine B (ErB), a commonly used dye for coloring foods and drinks, with bovine serum albumin (BSA) was investigated both in the absence and presence of bilirubin (BR) using absorption and absorption difference spectroscopy. ErB binding to BSA was reflected from a significant red shift of 11 nm in the absorption maximum of ErB (527 nm) with the change in absorbance at λmax. Analysis of absorption difference spectroscopic titration results of BSA with increasing concentrations of ErB using Benesi-Hildebrand equation gave the association constant, K as 6.9 104 M-1. BR displacing action of ErB was revealed by a significant blue shift in the absorption maximum, accompanied by a decrease in absorbance difference at λmax in the difference spectrum of BR-BSA complex upon addition of increasing concentrations of ErB. This was further substantiated by fluorescence spectroscopy, as addition of increasing concentrations of ErB to BR-BSA complex caused a significant decrease in fluorescence at 510 nm. The results suggest that ErB binds to a site in the vicinity of BR binding site on BSA. Therefore, intake of ErB may increase the risk of hyperbilirubinemia in the healthy subjects.