Juglone n. : A yellow crystalline substance resembling quinone, extracted from green shucks of the walnut (Juglans regia); -- called also nucin.

Example:
What happens if a human consumed Juglone?

Taxonomy
Juglone, hydroxy, compounds, free encyclopedia, plants, Aromatic compounds, plants and trees, search, 1,4-naphthoquinone, Identifiers, CC2, C1, g/mol, Appearance, 311, sol, Hazards, the leaves.

Defination from the web:
Juglone is an aromatic organic compound with the molecular formula C10H6O3. ... Juglone is an allelopathic compound, meaning it is synthesized by one type of plant and affects the growth of another. In the case of juglone, it is toxic or growth-stunting to many types of plants. ...