Investigation of double stranded DNA damage induced by quercetin-copper(II) using piezoelectric quartz crystal impedance technique and potentiometric stripping analysis.

DNA damage by quercetin-Cu(2+) was monitored in real time by piezoelectric quartz crystal impedance (PQCI) technique. In the PQCI analysis, the frequency change was caused mainly by the changes in density-viscosity of DNA solution in the damage course. The influences of DNA, Cu(2+), and quercetin concentrations on the motional resistance change (DeltaR(m)) were investigated in detail. The results showed that quercetin exhibited pro-oxidative damage at lower concentrations while anti-oxidative protection at higher concentrations, and DeltaR(m) exhibited a linear relationship in the DNA concentration range from 200 to 1600 microg/ml. Potentiometric stripping analysis (PSA) was also used to observe the electrochemical behavior of damaged DNA. From PSA, a new peak at 0.84 V and a higher peak at 1.06 V were discovered, which suggested that more purines were exposed to the electrode surface during the damage course. In agarose-gel electrophoresis, catalase and biquinoline were found to effectively inhibit DNA damage, therefore, a possible damage mechanism was proposed.