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

In this work a complex of Al3+ with curcumin ([Al(curcumin) (EtOH)2](NO3)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 Al3+ 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 × 104 and 2.6 × 104, 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 Al3+ to the DNA.

Graphical abstractThe study of interaction of Al–curcumin complex with ds-DNA, by multispectroscopic and voltammetric techniques.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► In Alzheimer's disease (AD) the Al3+ ions accumulated within the brain and interact with DNA. ► The results revealed the curcumine reduced the bonding affinity of Al3+ to DNA. ► A binding model of DNA-Al-curcumin has been developed by using a multispectroscopic and voltammetric techniques. ► The CD results showed that only the Δ-ACC interacts with DNA. ► The cyclic voltammetry showed that ACC interact with DNA with a bonding site size of 2. The Δ-ACC interacts with DNA via partial electrostatic and minor groove binding.