Curcumin-DNA Interaction Studied by Fourier Transform Infrared Spectroscopy

Curcumin is a non-toxic, dietary, natural polyphenol known for its potent antiinflammatory, antioxidant, antimutagenic and anticarcinogenic effects and also considered as a cancer chemo-preventive agent. The strong interaction of curcumin with biomolecules and the non-covalent interactions are known to play a decisive role in its mechanism of action. While the antioxidant activity of this polyphenolic compound is well known, their bindings to DNA are not fully investigated. The present study was designed to examine the interactions of curcumin with calf thymus DNA in aqueous solution at physiological conditions using constant DNA concentration (25mM) and various drug/DNA(phosphate) ratios of 1/50 to 1/5. Fourier Transform Infrared(FT-IR) spectroscopy was used to determine curcumin binding modes, the stability of DNA secondary structure in curcumin-DNA complexes in aqueous solution. Spectroscopic evidence shows that at low curcumin concentration(r=1/50) curcumin binding is mainly through the guanine N-7 atom(indirectly through H-bonding). When the concentration increases (r>1/10) drug binding to G,T,A and bases occurs(indirectly) with a partial helix stabilization as a result of weak intercalation into DNA duplex.