Spectroscopic Studies on the Interaction of Quercetin–Terbium(III) Complex with Calf Thymus DNA

Abstract

The interaction of native calf thymus DNA (CT-DNA) with quercetin-terbium(III) [Q-Tb(III)] complex at physiological pH was monitored by UV absorption spectrophotometry, circular dichroism, fluorescence spectroscopy, and viscosimetric techniques. The complex displays binding properties to the CT-DNA and was found to interact with CT-DNA through outside binding, demonstrated by a hypochromic effect of Q-Tb(III) on the UV spectra of CT-DNA and the calculated association constants (K). Also, decrease in the specific viscosity of CT-DNA, decrease in the fluorescence intensity of Q-Tb(III) solutions in the presence of increasing amounts of CT-DNA, and detectable changes in the circular dichroism spectrum of CT-DNA are other evidences to indicate that Q-Tb(III) complex interact with CT-DNA through outside binding.

Molecular aspects on the interaction of quercetin and its metal complexes with DNA

“…Recently, the enhanced fluorescence of Tb 3+ or Eu 3+ by complexation with organic ligands, such as phenanthroline and tetracycline has been used as a sensitive probe for the determination of nucleic acids. In particular, attention has been directed towards the enhancing effect of nucleic acids on the fluorescence of the lanthanide cation complex [3,18].…”

“…Match of shape and overlap between the quercetinmetal complexes and the B-DNA helix are the most important binding aspect of these molecules to DNA [3,15]. The application of mixed ligand complexes allows dissimilarity in the geometry, size, and hydrophobicity of the ligands and their substituents or in the metal, thus providing an opportunity to determine and also understand how these factors contribute to the affinity in DNA binding and cleavage.…”

“…Thus, several quercetin-metal complexes have been interacted with DNA. Recently, there has been substantial interest in the design and study of DNA binding and cleavage properties of quercetin-metal complexes and development of the complexes as metallodrugs [3,11,14].…”

“…Flavonoids, and particularly quercetin (Fig. 1) derivatives, have received more attention as dietary constituents during the last few years [3]. Many studies showed that flavonoids have a wide range of biological activities, such as anticancer, antiviral, antibacterial, antioxidants, and anti-inflammatory effects [4][5][6][7].…”

“…Flavonoids are best known as radical scavengers. While these valuable effects generally are due to their abilities to accept free radicals, complexation properties with metal ions have also been recognized to contribute to the total biological activity [3]. The experimental and theoretical studies showed that the ideal complexation site for flavonoids involves the hydroxyl group on carbon 3 or 5 and the adjacent 4-carbonyl group [3].…”