Photogeneration of reactive oxygen species and photoinduced plasmid DNA cleavage by novel synthetic chalcones

This paper describes the synthesis and photodynamic properties of six different chalcone derivatives. Using N,N-dimethyl-4-nitrosoaniline (RNO) bleaching assay, the singlet oxygen generating efficiencies of these chalcones are determined relative to rose bengal (RB). Superoxide dismutase (SOD) inhibitable cytochrome c reduction assay and electron magnetic resonance (EMR) spin trapping techniques are used to determine the superoxide anion radical (O2-) yield upon photoirradiation. Photoinduced DNA scission studies show that O2- is involved in the DNA strand break. In addition, antimicrobial activity of these chalcones is also investigated. Structure activity relationship accounts for the difference in the photogeneration of reactive oxygen species (ROS) by these sensitizers. Presence of electron releasing –OCH3 groups enhances the photogeneration of ROS. Cyclic voltammetry studies indicate a correlation between enzymatic O2- generation efficiency and redox potential of chalcones. Both O2- (Type I) and 1O2 (Type II) paths are involved in the photosensitization of chalcones. The LUMO energies obtained by molecular modeling correlate with the one-electron reduction potentials.

Research highlights
► Six novel chalcone derivatives are synthesized and characterized.
► The chalcones show photogeneration of ROS, as determined by optical and EPR methods.
► Both type I and type II mechanisms are involved in the photodynamic action.
► Redox potential and LUMO energy correlate with superoxide yield.
► The chalcones exhibit antimicrobial activity and photoinduced DNA scission.