nJuglone(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.
Century Dictionary and Cyclopedia
njugloneA yellowish- or brownish-red compound, HOC10H5O2. prepared by the oxidation of a-hydrojuglone from the green parts of the walnut-tree; a-hydroxynaphthoquinone, nucin, or regianin. It crystallizes in needles or prisms and melts at 151–154° C.
Webster's Revised Unabridged Dictionary
L. jugl,ans the walnut + -one,
Massey (1925) suggested that the toxic component of walnuts might be juglone.
"Northern Nut Growers Association Thirty-Fourth Annual Report 1943" by Various