Comparative studies of quercetin interactions with monophosphate nucleotides using UV-Vis spectroscopy and electrochemical techniques

The nature and extent of the interactions of phytoestrogens such as quercetin (Q) with monophosphate nucleotides have implications in cell cycle arrest, DNA damage, and inhibition of intracellular enzymes involved with cell proliferation. We have studied the interactions of quercetin with individual RNA/DNA monophosphate nucleotides using UV-vis spectroscopy, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) under physiological conditions. The monophosphate nucleotides studied included: guanosine 5-monophosphate (GMP), adenosine 5-monophosphate (AMP), deoxythymidine 5-monophosphate (TMP), and cytidine 5-monophosphate (CMP). Based on the characteristic absorption spectra isobestic points, hypochromism phenomenon, electrochemical shifts in peak potential and the changes in forward-to reverse peak currents (Δ I _pc/I_pa), the order of the affinity recorded was GMP > AMP > TMP > CMP respectively. The % Δ I_pc/I_pa recorded were 42.8, 78.6, 57.1, and 21.4 for Q:AMP, Q:GMP, Q:TMR and Q:CMP respectively, indicating an overall higher affinity for the purine nucleotides which is consistent with UV-vis results. The DPV data showed that the peak potentials shifted more positive with a simultaneous decrease in peak currents with increasing nucleotide concentrations, which were attributed to the Q-nucleotide adduct formation.