Naphthoquinones action

Reduction of monocyclic aromatic nitro compounds has been demonstrated (a) with reduced sulfur compounds mediated by a naphthoquinone or an iron porphyrin (Schwarzenbach et al. 1990), and (b) by Fe(II) and magnetite produced by the action of the anaerobic bacterium Geobacter metallireducens (Heijman et al. 1993). Quinone-mediated reduction of monocyclic aromatic nitro compounds by the supernatant monocyclic aromatic nitro compounds has been noted (Glaus et al. 1992), and these reactions may be signihcant in determining the fate of aromatic nitro compounds in reducing environments (Dunnivant et al. 1992). 

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. 

Anwar, M., T. H. Khan, J. Prebble, and R F. Zagalsky. 1977. Membrane-bound carotenoid in Micrococcus luteus protects naphthoquinone from photodynamic action. Nature 270 538-540. 

Atovaquone is a naphthoquinone whose mechanism of action involves inhibition of the mitochondrial electron transport system in the protozoa. Malaria parasites depend on de novo pyrimidine biosynthesis through dihy-droorotate dehydrogenase coupled to electron transport. Plasmodia are unable to salvage and recycle pyrimidines as do mammalian cells. 

More recently, a new class of insecticides derived from naphthoquinones found in the South American alpine plant Calceolaria andina has entered development. Compounds are being developed jointly through the British Technology Group (BTG) (following the discovery at Rothamsted Experimental Station) and by Bayer. The mode of action of these compounds is believed to be an inhibition of respiration at site... 

An interesting reaction is the formation of oxazoles (CLIII and CLIV) via heating the photoproducts, obtained by the action of aromatic aldehydes on the monoxime derivatives of CXLIX and CL, respectively. The oxazoles are readily obtained by allowing the aldehyde to react with the corresponding monoxime in the presence of piperidine in the dark.m-200 On the other hand, whereas irradiation of 1,2-naphthoquinone-1-benzoylimide (CLVI) with aromatic aldehydes led to CLVII, the monoimine derivative of CXLIX gave photoproducts of structures (CLVa or CLVb).198-199... 

The second method is that described above /3-naphthol is converted through the nitroso derivative and i-amino-2-naph-thol-4-sulfonic acid into naphthoquinone sulfonate, and this is subjected to acid hydrolysis. The sulfonate can be converted directly into hydroxynaphthoquinone by the action of concentrated sulfuric acid,3,4 but the process is not so easily controlled as when the quinone is etherified as it is formed, and the ether subsequently hydrolyzed.4 The overall yield from /3-naphthol is 46 per cent of the theoretical amount, but all the reagents are inexpensive, and with ordinary apparatus, 150 g. of hydroxynaphthoquinone can be made conveniently in one run (from 300 g. of /3-naphthol). 

The structure of vitamin Kj has been established by degradation and by synthesis. Surprisingly, the long alkyl side chain of vitamin K, is not necessary for its action in aiding blood clotting because 2-methyl-l,4-naphthoquinone is almost equally active on a molar basis. 

Human rhino viruses (HRVs) are the single most significant causative agents of the common cold. HRV 3C-protease, a cysteine protease, plays a critical role in the replication cycle of HRVs and thus constitutes a potential therapeutic target for the control of HRVs and common cold. Singh et al established the structure-activity relationships of various naphthoquinones as HRV 3C-proteasa inhibitors and compared the activities of ortho- versus -para- quinones. The results indicated that the mode of action of the two classes of compounds is different [207]. 

Prokopenko et al described that some naphthoquinones normalized or increased the immune response in rats after intensive physical load. The naphthoquinones induced the development of immunostimulating properties in heavy red blood cells by direct action on cell membranes or indirectly through proteolytic enzymes secreted by hepatocytes [212]. Other activities described for several naphthoquinones related to lapachol are antipsoriatic [213], larvicidal and insecticidal, [214-215] molluscicidal [216], and mutagenicity in salmonella [217]. The potential use of lapachol in cosmetics has been published too [218]. 

Several hundred semisynthetic derivatives have been prepared in an effort to obtain substances with better biological activities (for references see Ref.s)). Particularly positions 3 and 4 of the naphthoquinone ring system (numbering system as proposed by Prelog7 8) have been extensively substituted, since it has been shown that structural changes in these two positions do not critically affect the action of the substance on the target enzyme, the bacterial RNA polymerase (cf. Chapter 3.). They can, however, influence other parameters such as its ability to penetrate into cells, its pharmacokinetic properties and resorption, which are all important for clinical use as an antibiotic. Rifampicin (U.S. rifampin), which is a widely used orally active tuberculostatic agent, is a 3-(4-methyl piperazinyl)-iminomethyl derivative of rifamycin SV, synthesized via the 3-formyl derivative (Fig. 5)10 ... 

The conversion of 2-hydroxy-3 alkyl-l, 4-naphthoquinones by the action of alkaline permanganate into the next lower homolog has been extensively studied. A modified procedure involves the treatment of the naphthoquinone with hydrogen peroxide in dioxane-soda solution followed... 

An important support for this theory is the circumstance that the bodies formed by the action of aromatic hydrazines on quinones are identical with those obtained from phenols and diazo-compounds. Phenylhydrazine, for example, reacts with a-naphthoquinone, producing the same compound which is formed by combination of a-naphthol with diazobenzene [3j. The first method of formation renders the formula... 

Eurhodines are also formed by the action of triamidobenzene on /S-naphthoquinone, glyoxal, benzil, isatine, and leuconic acid. 

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