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Xenobiotic Metabolism
Published in Lorris G. Cockerham, Barbara S. Shane, Basic Environmental Toxicology, 2019
Larry G. Hansen, Barbara S. Shane
Benzo(a)pyrene (BP, Figure 3.5, I) is subject to P450-mediated activation reactions at several sites and often by successive oxidations. BP can be simultaneously activated to toxic intermediates (Figure 3.5, IV, VI) and deactivated to less toxic metabolites (Figure 3.5, V, XIII) by mixed function oxidases. These latter epoxides undergo hydrolysis by epoxide hydrolase to 1 and 3-hydroxybenzo(a)pyrene (Figure 3.5, XII, XVI) which are then conjugated by phase II enzymes to form excretory products. Although the 4,5-oxide (Figure 3.5, VI) is mutagenic, the pathway of major concern is I → II → III → IV. The diol epoxide (Figure 3.5, IV) can exist as (+) or (−) isomers, both with different potencies, but both can arylate nucleosides such as guanosine to form an adduct (Figure 3.5, XV). The 7,8-trans-dihydrodiol-9,10-epoxide (Figure 3.5, IV) is the most potent carcinogenic metabolite of BP. Many metabolites including the 3,6-quinone (Figure 3.5, X) and 1,6-quinone (Figure 3.5, IX) can be produced by more than one pathway. Although not as toxic as the 7,8-trans-dihydrodiol-9,10-epoxide, the quinones can cause tissue damage through redox cycling. The scheme represents most of the known metabolites of BP, although the number of actual and potential metabolites are more extensive.
Mineral Resources, Pollution Control, and Nanotechnology
Published in Stephen L. Gillett, Nanotechnology and the Resource Fallacy, 2018
Quinones, for example, a well-known redox system in organic chemistry, have been functionalized with cation-binding groups.40 Quinones readily and reversibly undergo reduction to the “hydroquinone” form (Fig. 6.3), and in fact are the basis of many biological electron-transfer reactions. The stoichiometry is Q + 2e-+ 2H+quinone (oxidized)↔QH2hydroquinone (reduced) $$ \mathop {{\text{Q + 2e}}^{{\text{ - }}} {\text{ + 2H}}^{{\text{ + }}} }\limits_{{{\text{quinone (oxidized)}}}} ~ \leftrightarrow ~\mathop {{\text{QH}}_{2} }\limits_{{{\text{hydroquinone (reduced)}}}} $$
Molecular Electronic Computing Architectures
Published in Sergey Edward Lyshevski, Nano and Molecular Electronics Handbook, 2018
James M. Tour, Dustin K. James
Many new molecules have recently been synthesized in our laboratories, and some have been tested in molecular electronics applications [66–69]. Since the discovery of the NDR behavior of the nitro aniline derivative, we have concentrated on the synthesis of oligo(phenylene ethynylene) derivatives. Scheme 2.1 shows the synthesis of a dinitro derivative. Quinones, found in nature as electron acceptors, can be easily reduced and oxidized, thus making them good candidates for study as molecular switches. The synthesis of one such candidate is shown in Scheme 2.2.
A review on bio-functional models of catechol oxidase probed by less explored first row transition metals
Published in Journal of Coordination Chemistry, 2022
Rashmi Rekha Tripathy, Shuvendu Singha, Sohini Sarkar
A particular concentration of the complex (preferably in the order of ∼10−4 M) is prepared in an appropriate solvent (acetonitrile/DMF/DMSO/methanol) and is treated with 100 times more concentrated solution of the substrate in the same solvent. The mixture is subjected to UV–vis spectra at a particular temperature (preferably room temperature) under aerobic condition for 60–90 min (saturation time). The activity can be monitored by appearance and gradual increase of intensity of the corresponding quinone band at ∼400 nm, indicating formation of quinone with time. However, depending upon the solvent and the complex used, the quinone absorption maxima may show a slight red shift and even sometimes a blue shift. The spectral change recorded can easily be compared with the blank experiment (obtained for the substrate without addition of complex) where no change is found even after 3 h of observation. A representative figure is shown in Figure 1.
Metal(II) complexes of bioactive aminonaphthoquinone-based ligand: synthesis, characterization and BSA binding, DNA binding/cleavage, and cytotoxicity studies
Published in Journal of Coordination Chemistry, 2018
A. Kosiha, C. Parthiban, Kuppanagounder P. Elango
Metal complexes of biologically active compounds are of paramount interest in pharmaceutical science due to their advantages such as they preserve the drugs against enzymatic degradation because of their higher stability, better hydrophilic/hydrophobic properties can be achieved for improved transport process in tissues, their activity can be reinforced by the combination of the properties of ligand and metal ion, they can release the active molecule in a specific location, etc. [1]. Quinones are widely distributed compounds in nature, catalyze various biochemical processes occurring in cells of living organisms and are found to have diverse pharmacological activities. Review of literature revealed that a number of quinone-based compounds have various biological activities like fungicidal, algicidal, herbicidal, bacterial, etc. [2]. Quinonoid compounds form a major part among the many natural and synthetic compounds screened for their anticancer activity [3]. The biological activity of quinones results from their ability to accept one or two electrons and also their acid–base properties [4, 5]. It is presumed that coordination of such quinone-based molecules with metal ions would enhance the biological activity of them when compared to free ligand. Though voluminous amount of works related to the biological activities of coordination complexes containing various types of bioactive substances are reported in literature [6, 7], similar studies with quinone-based ligands are very less [8–10] and hence the present study.
Cellular and biochemical antileukemic mechanisms of the meroterpenoid Oncocalyxone A
Published in Journal of Toxicology and Environmental Health, Part A, 2021
Aline Borba Sbardelotto, Francisco Washington Araújo Barros-Nepomuceno, Bruno Marques Soares, Bruno Coêlho Cavalcanti, Rayran Walter Ramos de Sousa, Marcília Pinheiro da Costa, Otília Deusdênia Loiola Pessoa, Cláudia Pessoa, Paulo Michel Pinheiro Ferreira
Quinones play a key role in biological functions since these compounds are electron transfer agents and participate in oxidative phosphorylation of electron transport chain during respiration and photosynthesis processes (Abraham et al. 2011). Quinones are highly electrophilic compounds found in dietary plant components and arise also from the metabolism of benzene, phenols, and other aromatics, including polycyclic aromatics of environmental origin. These compounds are classified based upon the aromatic system as benzoquinones, naphthoquinones, anthraquinones and phenantroquinones due to the presence of benzene, naphthalene, anthracene, and phenanthrene, respectively (Asche 2005; Monks et al. 1992; Monks and Jones 2002; Shukla et al. 2020).