|Jmol-3D images||Image 1|
|Molar mass||174.15 g mol−1|
|Melting point||162 to 163 °C (324 to 325 °F; 435 to 436 K)|
|Solubility in water||Slightly sol.|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Juglone, also called 5-hydroxy-1,4-naphthalenedione (IUPAC) is an organic compound with the molecular formula C8H6O(OH)2. In the food industry, juglone is also known as C.I. Natural Brown 7 and C.I. 75500. It is insoluble in benzene but soluble in dioxane, from which it crystallizes as yellow needles. It is an isomer of lawsone, which is the staining compound in the henna leaf.
Juglone occurs naturally in the leaves, roots, husks, fruit (the epicarp), 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.
The harmful effects of walnut trees on other plants have been observed for at least two millennia. However, juglone was not isolated until the 1850s. Two men, A. Vogel Jr. and C. Reischauer, were able to isolate the compound from the walnut tree in 1851. The compound was known as nucin at that time. Juglone was then synthesized and characterized for the first time in 1887 by A. Bernthsen and A. Semper. It was not until 1928 the compound was identified and confirmed to be toxic to other plants by E.F. Davis.
The use of walnut tree has historically been used within the field of traditional medicine. In America during the early 1900s, doctors prescribed juglone for the treatment of various skin diseases.
Chemistry and synthesis
Juglone is derived by oxidation of 1,5-dihydroxynaphthalene. It can be also be obtained by oxidations of 5,8-dihydroxy-1-tetralone with silver oxide (Ag2O), manganese dioxide (MnO2), or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).
Juglone is an example of allelopathic compound, a substance that is produced by a plant to stunt 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. It has also shown anthelmintic (expelling parasitic worms) activity on mature and immature Hymenolepis nana in mice. Antimicrobial activity of Napthoquinonic compounds.
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 dyess.
- J. Khalafy and J.M. Bruce (2002). "Oxidative dehydrogenation of 1-tetralones: Synthesis of juglone, naphthazarin, and α-hydroxyanthraquinones". Journal of Sciences, Islamic Republic of Iran 13 (2): 131–139.
- Juglone toxicity
- M. Strugstad (2012). "A Summary of Extraction, Synthesis, Properties, and Potential Uses of Juglone: A Literature Review". Journal of Ecosystems and Management 13 (3): 72–82.
- Gerald Booth "Naphthalene Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a17_009.
- Dama L.B. and Jadhav B.V. (1997). "Anthelmintic effect of Juglone on mature and Immature Hymenolepis nana in mice". Riv. Di Parassitol. 2: 301–302.
- Dama L.B., Poul B.N. and Jadhav B.V. (1998). "Antimicrobial activity of Napthoquinonic compounds". J. Ecotoxicol.Environ. Monit. 8: 213–215.
- Dama L.B., Poul B.N., Jadhav B.V and Hafeez MD. (1999). "Effect of "Juglone" on Development of the plant parasitic nematode (Meloidogyne Spp.) on Arachis hypogaea L.". J. Ecotoxicol. Environ. Monit. 9: 73–75.
- Dama L.B. (2002). "Effect of naturally occurring napthoquinones on root- knot nematode Meloidogyne spp.". Indian Phytopathology 55 (1): 67–69.