Electrochemical and spectroscopic investigation of bioactive naphthoquinones

The present work aims to investigate the electrochemical behavior of nine naphthoquinones, in aprotic and protic media. The reduction mechanism of the quinones in aprotic medium was proposed, with involvement of anion radical species, confirmed by performing in-situ Electrochemical-Electron Spin Resonance (E-ESR) experiments. Theoretical calculations using DFT method (U)B3LYP/6-31 were developed in order to rationalize the experimental hyperfine coupling constants. The results were in good agreement with the experimental data when solvent effects were included in the DFT models. © 2012 by ESG

Oncocalyxone A: Electrochemical, spectroscopic investigation and studies of its interaction with DNA, nucleobases and N-acetylcysteine

The formation of paramagnetic species from oncocalyxone A in aprotic medium was confirmed by performing in situ electrochemical-electron spin resonance (E-ESR) experiments. The high delocalization of the radical generated at the first reduction potential is clearly evidenced by the hyperfine coupling of H-9 with the larger coupling constant, besides the couplings at the H-3 (close to quinone) and H-7 (far from the quinone nucleus) positions. In protic medium, together with pH dependence experiments, oncocalyxone A showed to be DNA-reactive through experiments with DNA sensors. Its reaction with N-acetylcysteine, with structural characterization of the addition products, proved its ability as Michael acceptor. Both aspects are important in terms of biological/pharmacological activities and indicate the present models as important tools in the screening of biologically active compounds. © 2012 Sociedade Brasileira de Química