Abstract: The interaction between farrerol and calf thymus DNA (ctDNA) was explored by UV-visible spectrophotometry, fluorescence spectroscopy, and melting-point technique in combination with methylene blue (MB) competition in the presence of Cu2+, Co2+ and Mg2+ in physiological buffer (pH 7.4). The results revealed that farrerol could be intercalatively bound to DNA. Cu2+, Co2+ and Mg2+ had different effects on the absorption spectrum of farrerol and could increase the fluorescence intensity of DNA-MB complex. A gradual increase in Cu2+ concentration could result in an initial decrease followed by an increase in the binding constant of DNA-farrerol complex. In the presence of higher Mg2+ concentration, the binding constant of DNA-farrerol complex tended to initially increase and then decrease. However, Increasing Co2+ concentration revealed little effect on the binding constant of DNA-farrerol complex. Therefore, the effect of metal ions on the binding between farrerol and DNA mainly depends on the relative affinity between metal ions and farrerol, DNA basic groups or phosphate groups.

Key words: farrerol, calf thymus DNA, metal ions, fluorescence spectroscopy, binding mode