(Chem.) A yellow crystalline substance (C10H6O3) resembling quinone, extracted from green shucks of the walnut (Juglans regia); - called also nucin. Chemically, it is 5-hydroxy-1,4-naphthalenedione.
juglone
juglone
[′jəg‚lōn] (organic chemistry) C10H6O3 A naphthoquinone derivative that occurs naturally in black walnuts and is toxic to plants.