Juglone

Juglone
IUPAC name 5-hydroxy-1,4-naphthalenedione
Other names 5-hydroxy-1,4-naphthoquinone 5-hydroxy-p-naphthoquinone regianin
Identifiers
CAS number	481-39-0 Y
PubChem	3806
ChemSpider	3674 N
UNII	W6Q80SK9L6 Y
RTECS number	QJ5775000
Jmol-3D images	Image 1
SMILES O=C\2c1c(c(O)ccc1)C(=O)/C=C/2
InChI InChI=1S/C10H6O3/c11-7-4-5-9(13)10-6(7)2-1-3-8(10)12/h1-5,12H N Key: KQPYUDDGWXQXHS-UHFFFAOYSA-N N InChI=1/C10H6O3/c11-7-4-5-9(13)10-6(7)2-1-3-8(10)12/h1-5,12H Key: KQPYUDDGWXQXHS-UHFFFAOYAH
Properties
Molecular formula	C10H6O3
Molar mass	174.15 g/mol
Appearance	yellow solid
Solubility in water	slightly sol.
Hazards
R-phrases	R25
S-phrases	S28 S45
Related compounds
Related compounds	quinone
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Juglone, also called 5-hydroxy-1,4-naphthalenedione (IUPAC) or 5-hydroxynaphthoquinone, is an organic compound with the molecular formula C₁₀H₆O₃. In the food industry, juglone is also known as C.I. Natural Brown 7 and C.I. 75500. Other names in industry are Nucin, Regianin, NCI 2323, and Oil Red BS.

Juglone occurs naturally in the leaves, roots, husks, and bark of plants in the Juglandaceae family, particularly the black walnut (Juglans nigra), and is toxic or growth-stunting to many types of plants. It is sometimes used as a herbicide, as a dye for cloth and inks, and as a coloring agent for foods and cosmetics.

Chemistry and synthesis

Juglone is an aromatic compound, formally derived from 1,4-naphthoquinone through the replacement of one hydrogen atom by a hydroxyl (OH) group. It is an isomer of lawsone. It is insoluble in benzene but soluble in dioxane, from which it crystallizes as yellow needles that melt at 162–163 °C.

Juglone can be obtained from oxidation of 5,8-dihydroxy-1-tetralone with silver oxide (Ag₂O), manganese dioxide (MnO₂), or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).

Biological effects

Juglone is an example of allelopathic compound, a substance that is synthesized by one type of plant and affects the growth of another. Landscapers have long known that gardening underneath or near black walnut trees can be difficult. Juglone exerts its effect by inhibiting certain enzymes needed for metabolic function. A number of plants and trees are resistant to juglone including some species of maple (Acer), birch (Betula), and beech (Fagus).

It is highly toxic to many insect herbivores. Some of them, however, are capable of detoxification of juglone (and related naphthoquinones) to non-toxic 1,4,5-trihydroxynaphthalene.

Uses

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.

References

• Juglone toxicity