Naphthoquinones toxicity

Decahydro-2-naphthyl)propyl]-3-hydroxy-l,4-naphthoquinone, toxic effects of, VI, 40 menadione and, VI, 40, 41 vitamin K, and, VI, 40, 41 cts-Decalin,... 

In order to circumvent this problem, there has been significant activity directed toward the search for a less environmentally toxic and more selective oxidizing agent than chromium. For example, Hoechst has patented a process which uses organorhenium compounds. At a 75% conversion, a mixture of 86% of 2-methyl-l,4-naphthoquinone and 14% 6-methyl-l,4-naphthoquinone was obtained (60). Ceric sulfate (61) and electrochemistry (62,63) have also been used. 

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... 

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. 

Like for benzene, the cytotoxicity of naphthalene is not due to the epoxide but to the quinone metabolites, namely 1,2-naphthoquinone and 1,4-naphthoquinone [85], As shown in Table 10.1, naphthalene 1,2-oxide (10.2) is a better substrate than benzene oxide for epoxide hydrolase. Its rapid isomerization to naphthalen-l-ol, facile enzymatic hydration to the dihydrodiol and lack of reactivity toward nucleophiles such as glutathione may explain its absence of direct toxicity [85],... 

A. Liposomal amphotericin B was approved by the US. Food and Drug Administration to treat visceral leishmaniasis. Pentavalent antimony compounds, pentamidine, amphotericin B, and aminosi-dine (paromomycin) have all been demonstrated efficacious here. The liposomal amphotericin appears to be better taken up by the reticuloendothelial system, where the parasite resides, and partitions less in the kidney, where amphotericin B traditionally manifests its toxicity. In addition to being better tolerated by patients, it has proved to be very effective in India, where resistance to antimony drugs is widespread. This patient appears to have acquired his infection there, where many infected patients develop darkening of the skin, hence the name kala-azar, or black sickness. Albendazole, an anthelmintic, has no role here. Atovaquone, a naphthoquinone, is used to treat malaria, babesiosis, and pneumocystosis. Pyrimethamine-sulfadoxine is used to treat malaria and toxoplasmosis. Proguanil inhibits the dihydrofolate reductase of malaria parasites and is used in combination with atovaquone. 

The use of electricity in reactions is clean and, at least in some cases, can produce no waste. Toxic heavy metal ions need not be involved in the reaction. Hazardous or expensive reagents, if needed, can be generated in situ where contact with them will not occur. The actual oxidant is used in catalytic amounts, with its reduced form being reoxidized continuously by the electricity. In this way, 1 mol% of ruthenium(III) chloride can be used in aqueous sodium chloride to oxidize benzyl alcohol to benzaldehyde at 25°C in 80% yield. The benzaldehyde can, in turn, be oxidized to benzoic acid by the same system in 90% yield.289 The actual oxidant is ruthenium tetroxide. Naphthalene can be oxidized to naphthoquinone with 98% selectivity using a small amount of cerium salt in aqueous methanesulfonic acid when the cerium(III) that forms is reoxidized to cerium(IV) electrically.290 Substituted aromatic compounds can be oxidized to the corresponding phenols electrically with a platinum electrode in trifluoroacetic acid, tri-ethylamine, and methylene chloride.291 With ethyl benzoate, the product is a mixture of 44 34 22 o/m/fhhy-... 

Electrochemistry427 can be used to regenerate an expensive or toxic reagent in situ. An example is the electrical regeneration of periodate that is used for the oxidation of vicinal diols such as sugars. When used with osmium oxidations, it can keep the level of the toxic metal reagent quite low. In Chap. 4, an example of the conversion of a naphthoquinone to its epoxide by electrolysis of aqueous sodium iodide was given. The sodium hydroxide and iodine produced by electrolysis react to form hypoiodite that adds to the double bond to form the hydroxyiodide, which then eliminates sodium iodide by the action of the sodium hydroxide to re-form the sodium iodide.428 Electricity can be used in oxidations and... 

Leishmania, Trypanosoma and Plasmodium. Many naphthoquinones have been isolated but frequently their potential use has been limited by low bioavailability and high toxicity. Wright and Phillipson [62], Sepuvelda-Boza and Cassels [63], Foumet et al. [64] and Akendengue et al. [65] have reviewed much of the literature on naphthoquinones, we focus here on the latest developments and some new structures and their biological activities. 

The most basic structural model for anthracyclines adriamycin (doxorubicin) and daunomycin (daunorubicin) was considered to be tiie strongly intramolecularly hydrogen-bonded naphthazarin (5,8-dihydroxy-1,4-naphthoquinone) (Section 3.2). It is usually customary to study the way in which such simple quinones form radicals in order to gain insight into the way more complex quinones might produce toxic and other effects. This is more so as the radical centres in the complex molecules are usually located in these simpler model structures. Treatment of naphthazarin will also demonstrate how various data may be compiled and compared. 

Definition General term referring to a group of naphthoquinone derivs. required for the bioactivation of proteins involved in hemostasis Toxicoiogy LD50 (subcut., mouse) 700 mg/kg mod. toxic by subcut. route experimental teratogen TSCA listed... 

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