Interference of coumarin with the insertion of lyotropic anions and cadmium in artificial lipid bilayers

The interference of the natural polyphenol coumarin derivative, coumarin-3-carboxylic acid, with the insertion of lyotropic anions and cadmium into artificial lipid bilayers was investigated using the solid supported membrane (SSM) method. This electrophysiological method allows the study of artificial lipid membranes by successively applying substrate solutions of different concentrations ("concentration jumps"), which results in measurable capacitive currents. Heavy metals, like cadmium, and lyotropic or Hofmeister anions are among pollutants that can have noxious effects on living organisms. Therefore, it is of interest to try to find remedies to counteract or diminish their negative effects. An important number of studies have evidenced the beneficial role of polyphenols in the treatment and prevention of various human pathologies, due to both their antioxidant as well as prooxidant properties. In the present work, concentrations jumps of lyotropic anions and cadmium have been applied to artificial lipid membranes and the resulting electrical capacitive currents have been measured in the presence of several concentrations of the polyphenol coumarin. It has been found that in the presence of coumarin the electrical signals elicited by chaotropic anions and cadmium decreased significantly, suggesting a protective role of the polyphenol at the lipid bilayer level.