Interaction between ellagic acid and calf thymus DNA studied with flow linear dichroism UV-VIS spectroscopy

The interaction between ellagic acid and DNA has been characterized with respect to the geometry of the ellagic acid-DNA complex, and the active form of ellagic acid has been identified. Optical spectroscopic methods have been employed to examine the interaction between double-stranded calf thymus DNA and ellagic acid in low-ionic-strength aqueous solutions at pH values of 5.5, 7.0, and 8. 8. Based on normal absorption titration and flow linear dichroism experiments, it is confirmed that the neutral form of ellagic acid present at pH 5.5 binds to double-stranded DNA. It is found that the plane of the ellagic acid chromophore is positioned at an angle relative to the DNA helix axis, which is in accordance with intercalation of ellagic acid in DNA. It is concluded that at higher values of pH no or a very limited amount of ellagic acid binds to DNA. These results prove that the direct interaction between ellagic acid and DNA must be taken into account when evaluating the mechanism underlying the observed biological effects of this plant phenol.