REDOX PROPERTIES OF ECHINOCHROME-A

The electrochemical properties of polyhydroxynaphthoquinone from the s hells of sea-urchins Strongylocentrotus intermedius (echinochrome A) a nd related compounds were investigated using thin layer voltammetry on pyrolytic graphite electrodes. On the basis of experimental data pH-p otential diagrams for echinochrome A and its trimethyl ether are plott ed. Five different forms of echinochrome A and six forms of the trimet hyl ether of echinochrome A are shown to exist over the whole range of pH studied. Equilibrium constants and formal redox potentials for all conjugated forms are obtained. Electrochemical oxidation of echinochr ome A and its trimethyl ether lead to the formation of different produ cts. Tetraketotetralin is formed in the former case and naphthodiquino ne in the latter.