Binding studies of the antidiabetic drug, metformin to calf thymus DNA using multispectroscopic methods

Abstract

Interaction between antidiabetic drug, Metformin and calf thymus DNA (CT-DNA) in (50mM Tris–HCl) buffer were studied by UV–Visible absorption, fluorescence, CD spectroscopy and viscosity measurements. In fluorimetric studies, the enthalpy and entropy of the reaction between the drug and CT-DNA showed that the reaction is exothermic (ΔH=−35.4522kJmol−1; ΔS=−49.9523Jmol−1K−1). The competitive binding studies showed that the drug could release Hoechst 33258 completely. The complex showed absorption hyperchromism in its UV–Vis spectrum with DNA. The calculated binding constant, Kb, obtained from UV–Vis absorption studies was 8.3×104M−1. Moreover, the changes in the CD spectra in the presence of the drug show stabilization of the right-handed B form of CT-DNA. Finally, viscosity measurements revealed that the binding of the complex with CT-DNA could be surface binding, mainly due to groove binding.