Benzo pyrene-6,12-quinone

Benzo[a]pyrene-3,6-quinol and other quinols are involved in toxic quinone/quinol redox cycles (Lo-RENTZEN and Ts o 1977, Loeentzen etal. 1979). Quinols are formed from the corresponding qui-nones by several reductases. They are rapidly auto-xidizes while superoxide anions are formed. Benzo[fl]pyrene-3,6-quinone has been shown to be mutagenic in the Ames test, using tester strain TA 104 (Chesis et al. 1984) or TA 102, strains which are particularly sensitive to reactive oxygen species. In male Sprague-Dawley rats, a rapid increase of unmetabolised benzo[fl]pyrene was observed in sera 3h after benzo [a] pyrene treatment followed by a sharp decrease (Kim et al. 2000). The time-dependent pattern of serum lipid peroxidation and the level of erythrocyte antioxidant enzymes were shown to be related to the concentrations of the formation of benzo[ ]pyrene-quinones, oxidatively altered lipids and antioxidant enzymes in the blood. 

Trenck Tvd, H Sandermann (1981) Incorporation of benzo[a]pyrene quinones into lignin. FEES Lett 125 72-76. 

Gao, J. et al., 2005. Ryanodine receptor-mediated rapid increase in intracellular calcium induced by 7,8-benzo(a)pyrene quinone in human and murine leukocytes, Toxicol. Sci., 87, 419, 2005. 

Kim, S.H., Kwack, S.J., Lee, B.M. (2000). Lipid peroxidation, antioxidant enzymes and benzo(a)pyrene-quinones in the blood of rats treated with benzo(a)pyrene. Chem. Biol. Interact. 127 139-50. 

The incorporation of 3-chloroaniline and 3,4-diohloroaniline into copolymers with coniferyl alcohol in a similar model system was confirmed in a separate laboratory where the research was expanded to Include benzo(a)pyrene quinones (155). The copolymers were studied by H-NMR, nd other techniques. The copolymers of coni-... 

Rat liver microsomes also catalyzed benzo[a]pyrene metabolism in cumene hydroperoxide (CHP)-dependent reactions which ultimately produced 3-hydroxybenzo[a]pyrene and benzo[a]pyrene-quinones (Cavalieri et al. 1987). At low CHP concentrations, 3-hydroxybenzo[a]pyrene was the major metabolite. As CHP concentrations increased, levels of quinones increased and levels of 3- hydroxybenzo[a]pyrene decreased. This effect of varying CHP levels was reversed by preincubating with pyrene. Pyrene inhibited quinone production and increased 3-hydroxybenzo[a]pyrene production. Pretreatment with other PAHs like naphthalene, phenanthrene, and benz[a]anthracene nonspecifically inhibited the overall metabolism. The binding of benzo[a]pyrene to microsomal proteins correlated with quinone formation. This suggested that a reactive intermediate was a common precursor. The effects of pyrene on benzo[a]pyrene metabolism indicated that two distinct microsomal binding sites were responsible for the formation of 3-hydroxybenzo[a]pyrene and benzo[a]pyrene-quinone (Cavalieri et al. 1987). 

By HPLC the major reaction products of the BaP-D system were separated and tentative chemical structures were assigned to the peaks, based on the interpretation of the low and high resolution nS data as well as on comparison with reference spectra. The reaction mixture consisted mainly of ring-opened compounds such as dialdehyde and dicarboxylic acid, but also contained disubstitution products such as diphenols and quinones. The benzo(de)anthracene-7-one 3,4-dicarboxylic acid found in the reaction mixture is probably the precursor to the benzo(de)anthracene-7-one, detected by Sawicki (48) in the extract of ambient aerosols. The benzo(a)pyrene quinones were discovered in ambient air by Pierce and Katz (34). 

FIGURE 8.25 Quinones produced from pyrene and benzo[a]pyrene. (From Neilson, A.H. and Allard, A.-S. The Handbook of Environmental Chemistry, Springer, 1998. With permission.)... 

Although all quinones have the same functional group, their physicochemical behavior and mechanisms of toxicity vary due to the presence of different substituents. Thus, the cellular aspects of quinone metabolism are diverse, and a single mechanism explaining these actions has not yet been identified. Furthermore, it is noteworthy that the cytotoxicity of some xenobiotic compomids, such as benzene, benzo[a]pyrene, and 1-naphthol, may partly be caused by metabolic conversion of these compoimds to quinones (Snyder et al, 1987 Zheng et al, 1997). 

Chemical/Physical. Ozonolysis to benzo[a]pyrene-l,6-quinone or benzo [a] pyrene-3,6-quinone followed by additional oxidation to benzanthrone dicarboxylic anhydride was reported (lARC, 1983). 

In a simulated atmosphere, direct epoxidation by ozone led to the formation of benzo[a]pyrene-4,5-oxide. Benzo [a] pyrene reacted with benzoyl peroxide to form the 6-benzoyloxy derivative (quoted, Nikolaou et al, 1984). It was reported that benzo [a] pyrene adsorbed on fly ash and alumina reacted with sulfur dioxide (10%) in air to form benzo[a]pyrene sulfonic acid (Nielsen et al., 1983). Benzo [a] pyrene coated on a quartz surface was subjected to ozone and natural sunlight for 4 and 2 h, respectively. The compounds 1,6-quinone, 3,6-quinone, and the 6,12-quinone of benzo[a]pyrene were formed in both instances (Rajagopalan et al., 1983). 

Wislocki, P., A. Wood, R. Chang, W. Levin, H. Yagi, O. Hernandez, P. Dansette, D. Jerina, and A. Conney, Mutagenicity and Cytotoxicity of Benzo[u]pyrene, Arene Oxides, Phenols, Quinones, and Dihydrodiols in Bacterial and Mammalian Cells, Cancer Res., 36, 3350-3357 (1976). 

BenzoMpyrene /raw-4,5-dihydrodiol, benzoMpyrene /raw-7,8-dihydrodiol, benzo[tf]pyrene /raw-9,10-dihydrodiot, benzoU3pyrene-l,6-quinone, benzol>]pyrene-3,6-qui none, benzo[ s]pyrcnc-6,12-qui none,... 

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