5-Hydroxy-1,4-naphthalenedione

Description

Juglone (5-hydroxynapthoquinone), is found in the leaves and other parts of walnut, hickory and pecan (1,2). Juglone is synthesized from isochorismic acid (a product of the shikimic acid pathway) and 2-oxo-glutaric acid (3). In plant tissue juglone exists as a free compound or as a glycoside (3,4). Action of a glucosidase releases 1,4,5-trihydroxynapthalene, which is then oxidized to juglone (3,4).

Description

Juglone is a natural naphthoquinone found in the black walnut (J. nigra) and other plants in the Juglandaceae family. It has allelopathic actions, suppressing growth, photosynthesis, and respiration in plants and other organisms, although some bacteria can metabolize juglone. Juglone also irreversibly inhibits peptidyl-prolyl cis/trans isomerases of the parvulin family, including human Pin1, yeast Ess1/Ptf1, and E. coli parvulin (K_i = 55.9 nM). Juglone also blocks transcription by RNA polymerases I, II, and III (IC₅₀s = 2-7 μM) and attenuates kidney fibrosis in rats treated with unilateral ureteral obstruction, both through Pin1-independent mechanisms.

Chemical Properties

Orange to brown crystalline powder

Uses

antineoplastic, antifungal, antioxidant, Pin 1 inhibitor

Uses

5-Hydroxy-1,4-naphthoquinone is used as a natural dye in cloth, fabrics, wool and ink. It is a coloring agent for food and cosmetics. It is involved in the synthesis of poly(hydroxyl-1,4-naphthoquinone) stabilized gold nanoparticles (AuNQ NPs), which is used for nonenzymatic electrochemical detection of glucose.

Uses

Juglone (CI Natural Brown 7; CI 75500) was isolated from the husks of walnuts in 1856. Juglone occurs in walnuts as a glycoside of its reduced form, 1,4,5-trihydroxynaphthalene. Its structure is (3) Juglone is most readily synthesized by Bernthsen s method. It is a fungicide and as such finds use in the treatment of skin diseases. Its toxic properties have been made use of in catching fish. Juglone has been used to detect very small amount of nickel salts since it gives a deep violet color with such salts.

Definition

ChEBI: A hydroxy-1,4-naphthoquinone that is 1,4-naphthoquinone in which the hydrogen at position 5 has been replaced by a hydroxy group.

Synthesis Reference(s)

The Journal of Organic Chemistry, 48, p. 5160, 1983 DOI: 10.1021/jo00174a003
Synthetic Communications, 15, p. 1177, 1985 DOI: 10.1080/00397918508077262
Synthesis, p. 644, 1977 DOI: 10.1055/s-1977-24517

General Description

This substance is a primary reference substance with assigned absolute purity (considering chromatographic purity, water, residual solvents, inorganic impurities). The exact value can be found on the certificate. Produced by PhytoLab GmbH & Co. KG

Pharmacology

Juglone is probably best known as the allelochemical produced by black walnut. The glucoside of juglone leaches from the leaves and branches of black walnut, where it is converted to juglone in the soil. Juglone is toxic to certain plant species and also inhibits the germination of seeds (4). Thus its allelopathic activity may be the result of both phytotoxicity and a germination inhibitor. Juglone is also antifungal (1,5) and attempts to correlate its presence with disease resistance in pecan, black walnut, and hickory to several fungal pathogens have been reported (1,2,5,6). Positive correlations have been found for resistance of juvenile leaves of black walnut to anthracnose caused by Gnomia leptostyla (5) and of some Carya species to the scab pathogen Cladosporium carygenum (2). In some pecans (C. illinoensis), juglone may act as both a preformed and an induced defense factor because concentrations of juglone increase after infection by fungi (2). No correlation between juglone glycoside concentration in pecan leaves and resistance pecan to C. carygenum has been reported (6). Free juglone and the glycosides increase after infection, but these increases could not be correlated with scab resistance (6).

Purification Methods

Crystallise Juglone from *benzene/pet ether or pet ether. [Beilstein 8 III 2558, 8 IV 2368.]