The Collaborative International Dictionary
nucin
Juglone \Ju"glone\, n. [L. juglans the walnut + -one.] (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.
Wiktionary
nucin
n. juglone