ELECTROCHEMICAL PROPERTIES OF SOME NATURALLY-OCCURRING QUINONES

The electrochemical properties of some hydroxy-1,4-naphthoquinones of plant origin, namely juglon, lawson and plumbagin, have been investigated using thin layer voltammetry on pyrolytic graphite electrodes. The pH-potential diagrams for all three quinones are plotted on the basis of the experimental data. Five different forms of lawson and plumbagin and four forms of juglon are shown to exist in the whole range of pH. Equilibrium constants and formal redox potentials for all conjugated forms are obtained. © 1990.