Juglone 5-Hydroxy-1,4-naphthoquinone

The toxic influence exerted by Juglans nigra (black walnut) on other plants has been attributed to 5-hydroxy-1,4-naphthoquinone (juglone) (11,31). Hydrojuglone is present in the root bark, leaves, and fruit husks. This compound is not considered toxic, but it is oxidized to the toxic juglone upon exposure to air (51). Rainfall... 

The use of electroactive polymers as a DNA immobilization platform or as reporters of DNA hybridization was described in the literature. The immobilization of DNA using a polymer film is very simple, and the adsorption or covalent binding method can be applied simultaneously. The characterization of a biofunctional electroactive polymer, poly(5-hydroxy-1,4-naphthoquinone) (juglone)-co-5-hydroxy-3-thioacetic acid-1,4-naphthoquinone, used for direct... 

In 1885, from a detailed study of juglone (52) it was proposed that its stmcture was 5-hydroxy-l,4-naphthoquinone (9). This stmcture was confirmed by oxidizing 1,5-dihydroxynaphthalene with potassium dichromate in sulfuric acid (53). Juglone occurs in walnuts as a glycoside of its reduced form, 1,4,5-trihydroxynaphthalene (54). Later it was deterrnined that the sugar is in the 4-position (10) (55). 

Davis (19) in 1940 extracted and purified the toxic substance frcm the hulls and roots of walnut (JugIans) and found it to be identical to juglone (5-hydroxy-l,4-naphthoquinone). This compound proved to be a powerful toxin when injected into the stems of tomato, potato and alfalfa plants. The allelopathic action in the case of juglone (walnut tree and its vicinity) is well established. 

Juglone (= 2-Demethyl-plumbagin 5-Hydroxy-1,4-naphthalenedione Mucin Natural Brown 7 Regianin) (naphthoquinone)... 

Juglone (5-hydroxy-1,4-naphthoquinone) is a water-soluble yellow pigment that is exuded from leaves, fruits, bark, and roots of black walnut Juglans nigra), English walnut (J. regia), and hickory (Carya ovata) trees, among others. 

Naphthalene-1,5-diol and 4-dimethylaminoaniline in ethanol/water (1 1) stirred for 1 hour with 4 moles of potassium ferricyanide at ambient temperature and then diluted with water gave the quinoneimine shown in 85% yield (ref.194). The compound can be hydrolysed to juglone, 5-hydroxy-1,4-naphthoquinone. 

Although many of the products of the reaction were very polar, as shown by HPLC and thin-layer chromatography, we were able to determine some of the products by extracting the aqueous solution of a preparative-scale reaction done at pH 8 with diethyl ether and analyzing the extract by gas chromatography-mass spectroscopy (GC-MS). The principal ether-soluble product was 2-hydroxy-l,4-naphthoquinone (lawsone, 4). The mass spectrum of lawsone was sufficiently characteristic to distinguish it clearly from other hydroxynaphthoquinone isomers such as Juglone (11). Lawsone has also been reported previously as a product of photolysis of 1-naphthol in alkaline solution (12). 

Muller, W.U. and Leistner, E. (1976) Naphthoquinone, an intermediate in juglone (5-hydroxy-1,4-naphthoquinone) biosynthesis. Phytochemistry 15,407—110... 

Juglone, 5-hydroxy-l,4-naphthoquinone, is the principal colouring matter found in shells of various Juglandaceae (walnut),... 

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