ON THE NATURE OF SOLUBLE HYPERICIN IN HYPERICUM SPECIES

The two red and two violet ''soluble'' pigments of Hypericum species were isolated by means of extraction, chromatography, and counter-current droplet chromatography. In contrast to authentic hypericin, they are soluble in common organic solvents and even in water. Using NMR experiments it was deduced that hypericin, pseudohypericin, protohypericin, and protopseudohypericin are present in the plant as their rapidly interconverting 3- and 4-phenolate ions. From AAS the main counter-ion of these phenolates was derived to be potassium. The potassium and N-ethyl-N,N-diisopropylammonium salts of hypericin were synthesized for comparison. A preparative procedure to isolate hypericin and pseudohypericin from plant material was developed.