Juglone (5-hydroxy-1,4-naphthalenedione, C.I. Natural Brown 7, C.I. 75500) is an isomer of lawsone occurs naturally in the leaves, roots, husks, fruit (the epicarp), and bark of plants in the Juglandaceae family, particularly the black walnut (Juglans nigra). Juglone is an allelopathic compound, a substance that is produced by a plant to stunt the growth of another. Juglone is occasionally used as a herbicide. Traditionally, juglone has been used as a natural dye for clothing and fabrics, particularly wool, and as ink. Because of its tendency to create dark orange-brown stains, juglone has also found use as a coloring agent for foods and cosmetics, such as hair dyes. Juglone is currently being studied for its anticancer properties and It has been shown to decrease the probability of intestinal tumors in rats that have been exposed to carcinogens. One of the potential pathways through which juglone achieves its anticancer properties is through the formation of the semiquinone radical; the semiquinone radical causes superoxide anion radicals to form which can lead to apoptosis when present in large concentrations. This conversion from juglone to semiquinone radical that causes the superoxide anion radical to form takes place in the mitochondria as well as the cytosol.