Study binding of Al–curcumin complex to ds-DNA, monitoring by multispectroscopic and voltammetric techniques

Abstract

In this work a complex of Al 3+ with curcumin ([Al(curcumin) (EtOH) 2](NO 3) 2) was synthesized and characterized by UV–vis, FT-IR, elemental analysis and spectrophotometric titration techniques. The mole ratio plot revealed a 1:1 complex between Al 3+ and curcumin in solution. For binding studies of this complex to calf thymus-DNA various methods such as: UV–vis, fluorescence, circular dichroism (CD), FT-IR spectroscopy and cyclic voltammetry were used. The intrinsic binding constant of ACC with DNA at 25 °C was calculated by UV–vis and cyclic voltammetry as 2.1 × 10 4 and 2.6 × 10 4, respectively. The thermodynamic studies showed that the reaction is enthalpy and entropy favored. The CD results showed that only the Δ-ACC interacts with DNA and the Δ-ACC form has not any tendency to interact with DNA, also the pure curcumin has not any stereoselective interaction with CT-DNA. Fluorimetric studies showed that fluorescence enhancement was initiated by a static process in the ground state. The cyclic voltammetry showed that ACC interact with DNA with a binding site size of 2. From the FT-IR we concluded that the Δ-ACC interacts with DNA via partial electrostatic and minor groove binding. In comparison with previous works it was concluded that curcumin significantly reduced the affinity of Al 3+ to the DNA.