Structure-activity Studies of the Binding of the Flavonoid Scaffold to DNA

Background: Flavonoids have been shown to have a wide variety of biological activities and proven to be good scaffolds for the design of DNA-binding agents as anticancer therapeutics. Materials and Methods: In structure-activity relationship studies, flavonoid derivatives were designed and synthesised through various organic synthesis protocols, resulting in novel or previously described molecules. These were studied by UV-Vis absorbance and fluorescence spectroscopy as well as competition dialysis for their binding to DNA isoforms. Their cytotoxic potential was assessed using MTS assays on MCF-7 breast cancer and CCRFCEM leukaemia cell lines. Results and Conclusion: Introduction of moieties such as chloride, nitrogen, acetoxy and methoxy groups did not help to improve binding affinity, but introduction of tertiary amines improved the binding 1,000-fold due to an improved interaction of the compound with the nucleic acid; replacement of oxygen by sulphur increased the binding 7-fold, possibly because sulphur being less electronegative than oxygen would allow the electrons of the molecule to interact more strongly with the nucleic acid. Inhibition of growth by 50% (IG 50 ) values were moderate in breast and leukaemia cancer cell lines possibly due to the flavonoids interacting with other cellular components besides the nucleic acids.