Comparison of the Benzanthrone Luminophores: They Are Not Equal for Rapid Examination of Parafasciolopsis fasciolaemorpha (Trematoda: Digenea)

Luminescent derivatives of benzanthrone are becoming more useful based on their light-absorbing and fluorescent-emitting properties. Our previous studies showed that luminescent staining properties of the same benzanthrone dye differ for variable parasite samples. Therefore, two types of benzanthrone dyes were prepared. One has a strongly basic amidine group and a halogen atom, and the other has an amide moiety and a tertiary amine group. Trematoda Parafasciolopsis fasciolaemorpha is a liver fluke of a moose (Alces alces) and has a significant influence on the health and abundance of the moose population. Staining protocols for parasite P. fasciolaemorpha specific organ or organ systems imaging are mostly time-consuming and labor-intensive. The study aimed to compare the fixation technique and the staining protocol by synthesized benzanthrone luminescent dyes to determine detailed morphology, anatomical arrangement of the organ systems and gross organization of the muscle layers of P. fasciolaemorpha using confocal laser scanning microscopy. Luminophores were tested for samples fixed in different fixatives. Developed dyes and staining protocol resulting in imaging of all parts of trematode without additional sample preparation procedures, which usually are required for parasite examination. Obtained results confirmed that the most qualitative results could be reached using 3-N-(2-piperidinylacetamido)benzanthrone dye which has amide moiety and a tertiary amine group. Based on obtained results, 3-N-(2-piperidinylacetamido)benzanthrone gave more qualitative parasite visualization than 2-bromo-3-N-(N′,N′-dimethylformamidino)benzanthrone.

Structure-activity relationships and mechanism of action of tetragomycin derivatives as inhibitors of Staphylococcus aureus staphyloxanthin biosynthesis

Despite the main strategy to overcome bacterial resistance has focused on the development of more potent antimicrobial agents, the evolutionary pressure caused by such drugs makes this strategy limited. Molecules that interfere with virulence factors appear as a promising alternative though, as they cause reduced selective pressure. As a matter of fact, staphyloxanthin biosynthesis inhibition (STXBI) has been pursued as promising strategy to reduce S. aureus virulence. Herein, we report the inhibitory profile of 27 tetrangomycin derivatives over staphyloxanthin production. The experimental result showed that naphthoquinone dehydro-α-lapachone (25 - EC₅₀ = 57.29 ± 1.15 μM) and 2-Isopropylnaphtho[2,3-b]furan-4,9-dione (26 EC₅₀ = 82.10 ± 1.09 μM) are the most potent compounds and suggest that hydrogen acceptor groups and lipophilic moieties decorating the naphthoquinone ring are crucial for STXBI. In addition, we present an in situ analysis, through RAMAN spectroscopy, that is inexpensive and might be employed to probe the mechanism of action of staphyloxanthin biosynthesis inhibitors. Therefore, our molecular simplification strategies afforded promising lead compounds for the development of drugs that modulate S. aureus staphyloxanthin biosynthesis.

Fluorine-Containing Dibenzoanthracene and Benzoperylene-Type Polycyclic Aromatic Hydrocarbons: Synthesis, Structure, and Basic Chemical Properties

Intramolecular photocyclization of stilbene derivatives (Mallory reaction) is one of the efficient methods for building polycyclic aromatic hydrocarbon (PAH) frameworks, and is also expected to be applicable to synthesis of fluorine-containing PAHs (F-PAHs). In this study, dibenzoanthracene-type (4a) and benzoperylene-type (4b) F-PAHs were synthesized using the Mallory reaction of the 1,4-distyrylbenzene-type π-conjugated molecule (3a), which was prepared by addition-defluorination of available octafluorocyclopentene (OFCP) and aryllithium in three steps. The structure of 4a originating from π⁻π interaction was characterized by X-ray crystallographic analysis. The absorption maxima of UV-Vis spectra and emission maxima of photoluminescence spectra of the PAHs were positioned at a longer wavelength compared to those of the corresponding unsubstituted PAHs, presumably due to the electron-withdrawing nature of perfluorocyclopentene (PFCP) units. The effect of PFCP units in F-PAHs was also studied by time-dependent density functional theory (TD-DFT) calculation.

Novel luminescent dyes for confocal laser scanning microscopy used in Trematoda parasite diagnostics

Benzanthrone derivates are now widely used in many industrial and scientific applications as dyes for polymers and textiles. In biochemical, biomedical and diagnostics investigations benzanthrone dyes are used as a lipophilic fluorescent probe since many benzanthrone derivates demonstrate bright fluorescence and they have ability to intercalate between membrane lipids. The aim of research presented here was to assess the luminescence ability of benzanthrone derivatives using microscopic visualization of biological objects. Accordingly, specimens of freshwater trematodes: Diplostomum spathaceum, Diplodiscus subclavatus and Prosotocus confusus, were stained by novel benzanthrone dyes using different fixatives. The samples were examined under a confocal laser scanning microscope. All of the dyes tested demonstrated good results for digestive and reproductive system visualization. Based on obtained results we conclude that benzanthrone dyes could be used for internal and external structure confocal laser scanning microscopic imaging of trematode specimens.

Experimental and theoretical study on structure and spectroscopic properties of 2-bromo-3-N-(N',N'-dimethylformamidino) benzanthrone

The goal of present research is a theoretical and experimental investigation of geometrical structure, electronic properties, absorption and fluorescence spectra prediction for 2-bromo-3-N-(N',N'-dimethylformamidino)benzanthrone. As a result of conformational analysis, two rotamers have been found with a rotational barrier of 5.45 kcal/mol. Absorption and fluorescence spectra maxima in the solvent (ethanol) have been calculated using the concepts of the Jablonsky diagram. The obtained values of the absorption and fluorescence maxima (437 and 679 nm, respectively) correspond to the experimental values (447 and 659 nm). The abnormally large Stokes shift is associated with the redistribution of electron density, as well as flattening of the structure of the molecule in the excited state. According to the frontal molecular orbital analysis data, the peak in the long-wave part of the absorption spectra is created by an electron transition from the highest occupied molecular orbital (HOMO) to the lowest occupied molecular orbital (LUMO) (π→π*). Substitute group does not participate in the formation of absorption and fluorescence spectra.

Mechanism of Error-Free Bypass of the Environmental Carcinogen N-(2'-Deoxyguanosin-8-yl)-3-aminobenzanthrone Adduct by Human DNA Polymerase η

The environmental pollutant 3-nitrobenzanthrone produces bulky aminobenzanthrone (ABA) DNA adducts with both guanine and adenine nucleobases. A major product occurs at the C8 position of guanine (C8-dG-ABA). These adducts present a strong block to replicative polymerases but, remarkably, can be bypassed in a largely error-free manner by the human Y-family polymerase η (hPol η). Here, we report the crystal structure of a ternary Pol⋅DNA⋅dCTP complex between a C8-dG-ABA-containing template:primer duplex and hPol η. The complex was captured at the insertion stage and provides crucial insight into the mechanism of error-free bypass of this bulky lesion. Specifically, bypass involves accommodation of the ABA moiety inside a hydrophobic cleft to the side of the enzyme active site and formation of an intra-nucleotide hydrogen bond between the phosphate and ABA amino moiety, allowing the adducted guanine to form a standard Watson-Crick pair with the incoming dCTP.

Bioaccessibility of nitro- and oxy-PAHs in fuel soot assessed by an in vitro digestive model with absorptive sink

Ingestion of soot present in soil or other environmental particles is expected to be an important route of exposure to nitro and oxygenated derivatives of polycyclic aromatic hydrocarbons (PAHs). We measured the apparent bioaccessibility (B_app) of native concentrations of 1-nitropyrene (1N-PYR), 9-fluorenone (9FLO), anthracene-9,10-dione (ATQ), benzo[a]anthracene-7,12-dione (BaAQ), and benzanthrone (BZO) in a composite fuel soot sample using a previously-developed in vitro human gastrointestinal model that includes silicone sheet as a third-phase absorptive sink. Along with B_app, we determined the 24-h sheet-digestive fluid partition coefficient (K_s,24h), the soot residue-fluid distribution ratio of the labile sorbed fraction after digestion (K_r,lab), and the maximum possible (limiting) bioaccessibility, B_lim. The B_app of PAH derivatives was positively affected by the presence of the sheet due to mass-action removal of the sorbed compounds. In all cases B_app increased with imposition of fed conditions. The enhancement of B_app under fed conditions is due to increasingly favorable mass transfer of target compounds from soot to fluid (increasing bile acid concentration, or adding food lipids) or transfer from fluid to sheet (by raising small intestinal pH). Food lipids may also enhance B_app by mobilizing contaminants from nonlabile to labile states of the soot. Compared to the parent PAH, the derivatives had larger K_r,lab, despite having lower partition coefficients to various hydrophobic reference phases including silicone sheet. The B_lim of the derivatives under the default conditions of the model ranged from 65.5% to 34.4%, in the order, 1N-PYR > ATQ > 9FLO > BZO > BaAQ, with no significant correlation with hydrophobic parameters, nor consistent relationship with B_lim of the parent PAH. Consistent with earlier experiments on a wider range of PAHs, the results suggest that a major determinant of bioaccessibility is the distribution of chemical between nonlabile and labile states in the original solid.

Vibrational and electronic spectra of 2-nitrobenzanthrone: An experimental and computational study

The environmental pollutant 2-nitrobenzanthrone (2-NBA) poses human health hazards, and is formed by atmospheric reactions of NOX gases with atmospheric particulates. Though its mutagenic effects have been studied in biological systems, its comprehensive spectroscopic experimental data are scarce. Thus, vibrational and optical spectroscopic analysis (UV-Vis, and fluorescence) of 2-NBA was studied using both experimental and density functional theory employing B3LYP method with 6-311+G(d,p) basis set. The scaled theoretical vibrational frequencies show good agreement to experiment to within ~5 cm(-1) and <20 cm(-1) for frequencies <1800 cm(-1) and 2700-3200 cm(-1), respectively. In addition, predictions of the DFT frequencies below 1800 cm(-1) yield an overall root mean square (RMS) of ±20.1 and ±20.6 cm(-1) for benzanthrone and 2-NBA, respectively. On the basis of normal coordinate analysis complete assignments of harmonic experimental infrared and Raman bands are made. The influence of the nitro group substitution upon the benzanthrone structure and symmetric CH vibrations, and electronic spectra is noted. This study is useful for the development of spectroscopy-mutagenicity relationships in nitrated polycyclic aromatic hydrocarbons.

Superoxide mediated photomodification and DNA damage induced apoptosis by Benz(a)anthracene via mitochondrial mediated pathway

Benz(a)anthracene (BA) is an ubiquitous environmental pollutant of polycyclic aromatic hydrocarbon's (PAHs) family. We showed superoxide (O2(-)) catalyzed BA photo modification and apoptosis in HaCaT keratinocytes under sunlight exposure. O2(-) generation was confirmed by quenching through superoxide dismutase (SOD). BA induced photocytotoxicity were investigated through MTT and NRU assay. We proposed DNA insults such as single and double strand breakage and CPDs formation which results in cell cycle arrest and apoptosis by photosensitized BA. BA induced apoptosis was caspase dependent and occurred through a mitochondrial pathway. Reduction of mitochondrial membrane potential, translocation of Bax to mitochondria and cytochrome c release favors involvement of mitochondria in BA phototoxicity. AO/EB double staining and TEM analysis also support apoptotic cell death. We propose a p21 regulated apoptosis via expression of Bax, and cleaved PARP under sunlight exposure. Thus, we conclude that it is imperative to avoid solar radiation during peak hr (between 11A.M. and 3P.M.) when the amount of solar radiation is high, in the light of DNA damage which may lead to mutation or skin cancer through photosensitized BA under sunlight exposure. Concomitantly, investigation is urgently required for the photosafety of BA photoproducts reaching in the environment through photomodification.

Effect-directed analysis of Elizabeth River porewater: developmental toxicity in zebrafish (Danio rerio)

In the present study, effect-directed analysis was used to identify teratogenic compounds in porewater collected from a Superfund site along the Elizabeth River estuary (VA, USA). Zebrafish (Danio rerio) exposed to the porewater displayed acute developmental toxicity and cardiac teratogenesis, presumably because of elevated sediment levels of polycyclic aromatic hydrocarbons (PAHs) from historical creosote use. Pretreatment of porewater with several physical and chemical particle removal methods revealed that colloid-bound chemicals constituted the bulk of the observed toxicity. Size-exclusive chromatography and normal-phase high-performance liquid chromatography were used to fractionate Elizabeth River porewater. Acute toxicity of porewater extracts and extract fractions was assessed as the pericardial area in embryonic zebrafish. The most toxic fraction contained several known aryl hydrocarbon receptor (AhR) agonists (e.g., 1,2-benzofluorene and 1,2-benzanthracene) and cytochrome P450 A1 (CPY1A) inhibitors (e.g., dibenzothiophene and fluoranthene). The second most toxic fraction contained known AhR agonists (e.g., benzo[a]pyrene and indeno[1,2,3-cd]pyrene). Addition of a CYP1A inhibitor, fluoranthene, increased toxicity in all active porewater fractions, suggesting synergism between several contaminants present in porewaters. The results indicate that the observed acute toxicity associated with Elizabeth River porewater results from high concentrations of AhR agonistic PAHs and mixture effects related to interactions between compounds co-occurring at the Elizabeth River site. However, even after extensive fractionation and chemical characterization, it remains plausible that some active compounds in Elizabeth River porewater remain unidentified.

Altertoxins with potent anti-HIV activity from Alternaria tenuissima QUE1Se, a fungal endophyte of Quercus emoryi

Screening of a small library of natural product extracts derived from endophytic fungi of the Sonoran desert plants in a cell-based anti-HIV assay involving T-cells infected with the HIV-1 virus identified the EtOAc extract of a fermentation broth of Alternaria tenuissima QUE1Se inhabiting the stem tissue of Quercus emoryi as a promising candidate for further investigation. Bioactivity-guided fractionation of this extract led to the isolation and identification of two new metabolites, altertoxins V (1) and VI (2) together with the known compounds, altertoxins I (3), II (4), and III (5). The structures of 1 and 2 were determined by detailed spectroscopic analysis and those of 3-5 were established by comparison with reported data. When tested in our cell-based assay at concentrations insignificantly toxic to T-cells, altertoxins V (1), I (3), II (4), and III (5) completely inhibited replication of the HIV-1 virus at concentrations of 0.50, 2.20, 0.30, and 1.50 μM, respectively. Our findings suggest that the epoxyperylene structural scaffold in altertoxins may be manipulated to produce potent anti-HIV therapeutics.

Mechanisms of enzyme-catalyzed reduction of two carcinogenic nitro-aromatics, 3-nitrobenzanthrone and aristolochic acid I: Experimental and theoretical approaches

This review summarizes the results found in studies investigating the enzymatic activation of two genotoxic nitro-aromatics, an environmental pollutant and carcinogen 3-nitrobenzanthrone (3-NBA) and a natural plant nephrotoxin and carcinogen aristolochic acid I (AAI), to reactive species forming covalent DNA adducts. Experimental and theoretical approaches determined the reasons why human

NAD(P)H

quinone oxidoreductase (NQO1) and cytochromes P450 (CYP) 1A1 and 1A2 have the potential to reductively activate both nitro-aromatics. The results also contributed to the elucidation of the molecular mechanisms of these reactions. The contribution of conjugation enzymes such as N,O-acetyltransferases (NATs) and sulfotransferases (SULTs) to the activation of 3-NBA and AAI was also examined. The results indicated differences in the abilities of 3-NBA and AAI metabolites to be further activated by these conjugation enzymes. The formation of DNA adducts generated by both carcinogens during their reductive activation by the NOQ1 and CYP1A1/2 enzymes was investigated with pure enzymes, enzymes present in subcellular cytosolic and microsomal fractions, selective inhibitors, and animal models (including knock-out and humanized animals). For the theoretical approaches, flexible in silico docking methods as well as ab initio calculations were employed. The results summarized in this review demonstrate that a combination of experimental and theoretical approaches is a useful tool to study the enzyme-mediated reaction mechanisms of 3-NBA and AAI reduction.

The molecular properties of nitrobenzanthrone isomers and their mutagenic activities

The mutagenic activity of five mono-substituted nitrobenzanthrones (NBA) has been determined in the Ames assay (Takamura-Enya et al., 2006). In the present study, a theoretical investigation of the electronic properties of all mono-substituted NBA isomers and their relation to mutagenic activity are presented. Equilibrium geometries, vertical ionization potentials (VIP), vertical electron affinities (VEA), relative energies, dipole moments and electronic dipole polarizabilities, and the IR and Raman spectra of NBA isomers calculated by Density Functional Theory (DFT) methods are presented. The position of the nitro group affects the spectral features of the IR and Raman spectra of the NBA isomers. The results show that a good linear relationship exists between the summation of Raman activities (∑ARaman) over all the 3N-6 vibrational modes and the mutagenic activity of the NBA isomers in Salmonella typhimurium strains. The spectroscopic results suggest that the unknown mutagenic activities of 4-NBA, 5-NBA, 6-NBA, 8-NBA and 10-NBA are predicted to follow the order 4-NBA>10-NBA>5-NBA>8-NBA>6-NBA.

A new compound from an endophytic fungus Alternaria tenuissima

A new secondary metabolite, named altertoxin IV (1), together with altertoxin II (2), was isolated from the fermentation broth of Alternaria tenuissima, an endophytic fungal strain residing in the stem of Tribulus terrestris L. The structure of new compound 1 was established by HR-ESI-MS, multinuclear NMR spectroscopy, and single crystal X-ray diffraction method. In their in vitro bioassay, compound 2 exhibited moderate cytotoxic activity against PC-3 cell lines with an IC50 value of 14.28 μM.

Nitroaromatic compounds: Environmental toxicity, carcinogenicity, mutagenicity, therapy and mechanism

Vehicle pollution is an increasing problem in the industrial world. Aromatic nitro compounds comprise a significant portion of the threat. In this review, the class includes nitro derivatives of benzene, biphenyls, naphthalenes, benzanthrone and polycyclic aromatic hydrocarbons, plus nitroheteroaromatic compounds. The numerous toxic manifestations are discussed. An appreciable number of drugs incorporate the nitroaromatic structure. The mechanistic aspects of both toxicity and therapy are addressed in the context of a unifying mechanism involving electron transfer, reactive oxygen species, oxidative stress and antioxidants.

Aqueous solubility (in the range between 298.15 and 338.15 K), vapor pressures (in the range between 10(-5) and 80 Pa) and Henry's law constant of 1,2,3,4-dibenzanthracene and 1,2,5,6-dibenzanthracene

Aqueous solubility and vapor pressures of 1,2,3,4-dibenzanthracene and 1,2,5,6-dibenzanthracene were determined using dynamic saturation methods. For the two isomers, aqueous solubility is in the range between 10(-10) and 10(-2) in molar fraction corresponding to temperature between 298.15 and 338.15K. Vapor pressures of the pure solutes range from 10(-5) to 80 Pa. Prior to the study of the two dibenzanthracenes and in order to check the experimental procedures, solubility of fluoranthene (between 298 and 338 K) and vapor pressures of phenanthrene and fluoranthene (between 300 and 470 K) were measured. From aqueous solubility data coupled with the vapor pressures of the pure solutes, partition coefficient air-water, KAW, and Henry's constant, KH, of environmental relevance were calculated.

Fluorescent substituted amidines of benzanthrone: synthesis, spectroscopy and quantum chemical calculations

Several new substituted amidine derivatives of benzanthrone were synthesized by a condensation reaction from 3-aminobenzo[de]anthracen-7-one and appropriate aromatic and aliphatic amides. The obtained derivatives have a bright yellow or orange fluorescence in organic solvents and in solid state. The novel benzanthrone derivatives were characterized by TLC analysis, (1)H NMR, IR, MS, UV/vis, and fluorescence spectroscopy. The solvent effect on photophysical behaviors of these dyes was investigated, and the results showed that the Stoke's shift increased, whereas quantum yield decreased with the growth of the solvent polarity. The structure of some dyes was confirmed by the X-ray single crystal structure analysis. AM1, ZINDO/S and ab initio calculations using Gaussian software were carried out to estimate the electron system of structures. The calculations show planar configurations for the aromatic core of these compounds and two possible orientations of amidine substituents. The calculation results correlate well with red-shifted absorption and emission spectra of compounds.

Thermochemical properties and phase behavior of halogenated polycyclic aromatic hydrocarbons

Knowledge of vapor pressure of organic pollutants is essential in predicting their fate and transport in the environment. In the present study, the vapor pressures of 12 halogenated polycyclic aromatic compounds (PACs), 9-chlorofluorene, 2,7-dichlorofluorene, 2-bromofluorene, 9-bromofluorene, 2,7-dibromofluorene, 2-bromoanthracene, 9-chlorophenanthrene, 9-bromophenanthrene, 9,10-dibromophenanthrene, 1-chloropyrene, 7-bromobenz[a]anthracene, and 6,12-dibromochrysene, were measured using the Knudsen effusion method over the temperature range of 301 to 464 K. Enthalpies and entropies of sublimation of these compounds were determined via application of the Clausius-Clapeyron equation. The data were also compared with earlier published literature values to study the influence of halogen substitution on vapor pressure of PACs. As expected, the halogen substitution decreases vapor pressure compared with parent compounds but does not necessarily increase the enthalpy of sublimation. Furthermore, the decrease of vapor pressure also depends on the substitution position and the substituted halogen, and the di-substitution of chlorine and/or bromine decreases the vapor pressure compared with single halogen-substituted polycyclic aromatic hydrocarbons. In addition, the enthalpy of fusion and melting temperature of these 12 PACs were determined using differential scanning calorimetry and melting point analysis.

Carcinogenic 3-nitrobenzanthrone but not 2-nitrobenzanthrone is metabolised to an unusual mercapturic acid in rats

3-Nitrobenzanthrone (3-NBA) is an extremely potent mutagen and suspect human carcinogen found in diesel exhaust. Its isomer 2-nitrobenzanthrone (2-NBA) has also been found in ambient air. These isomers differ in mutagenicity in Salmonella by 2-3 orders of magnitude. To identify their urinary metabolites and also to assess the assumed differences in their excretion, rats were dosed orally with 2mg/kg b.w. of either 2-NBA or 3-NBA. Their urine was collected for two consecutive days after dosage. Both LC-ESI-MS and GC-MS confirmed formation of the corresponding aminobenzanthrones (ABA). Excretion of these metabolites within the first day after dosing with 2- and 3-ABA amounted to 0.32±0.06 and 0.83±0.40% of the doses, respectively, while the excretion within the second day was by one order of magnitude lower. A novel mercapturic acid metabolite of 3-NBA was identified in urine by LC-ESI-MS as N-acetyl-S-(3-aminobenzanthron-2-yl)cysteine (3-ABA-MA) by comparison with the authentic standard. Its excretion amounted to 0.49±0.15 and 0.02±0.01% of dose within the first and second day after dosing, respectively. In contrast, no mercapturic acid was detected in the urine of rats dosed with 2-NBA. Observed difference in the mercapturic acid formation between 2- and 3-NBA is a new distinctive feature reflecting differences in the critical step of their metabolism, i.e., benzanthronylnitrenium ion formation that is intrinsically associated with biological activities of these two isomers. Moreover, 3-ABA-MA is a promising candidate biomarker of exposure to the carcinogenic 3-NBA.

Mayamycin, a cytotoxic polyketide from a Streptomyces strain isolated from the marine sponge Halichondria panicea

A new benz[a]anthracene derivative called mayamycin (1) was identified in cultures of Streptomyces sp. strain HB202, which was isolated from the marine sponge Halichondria panicea and selected because of its profound antibiotic activity. The ability to produce aromatic polyketides was indicated by genetic analyses, demonstrating the presence of a type II polyketide synthase. The production of mayamycin (1) was induced by variation of the culture conditions. The structure of 1 was elucidated by HPLC-UV/MS and NMR spectroscopy. Mayamycin (1) exhibited potent cytotoxic activity against eight human cancer cell lines and showed activity against several bacteria including antibiotic-resistant strains.

Heterologous cross-expression of oxygenase and glycosyltransferase genes in streptomycetes, producing angucyclic antibiotics

The heterologous expression of oxygenase genes urdM, ovmOIII, lanM2, IndZ5 and glycosyltransferase gene urdGT2 in different angucycline producers of genus Streptomyces has been carried out. The introduction of genes urdM, lanM2 and urdGT2 results in the accumulation of new glycosylated compounds in several strains under investigation. A number of processed recombinant strains display streptomycin sensitivity and decrease in total antibacterial activity. The obtained data is an evidence of changes in antibiotics production, resulting from post-polyketide synthase (post-PKS) tailoring gene expression across streptomycete strains. Our study demonstrates the potential of post-PKS tailoring genes for generation of novel bioactive metabolites.

Structural identification of DNA adducts derived from 3-nitrobenzanthrone, a potent carcinogen present in the atmosphere

3-Nitrobenzanthrone is a powerful bacterial mutagen and carcinogen to mammals. To obtain precise information on DNA-adduct formation by 3-nitrobenzanthrone, a number of DNA adducts, including N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone (13 a), 2-(2'-deoxyguanosin-N2-yl)-3-aminobenzanthrone (14 a), N-(2'-deoxyadenosin-8-yl)-3-aminobenzanthrone (15 a), 2-(2'-deoxyadenosin-N6-yl)-3-aminobenzanthrone (16 a), and their N-acetylated counterparts 13 b, 14 b, 15 b, and 16 b were synthesized by palladium-catalyzed aryl amination of the corresponding nucleoside and bromobenzanthrone derivatives. Among these DNA adducts, DNA adducts 13 a, 13 b, 14 a, 14 b, and 16 a were identified in the reaction mixture of nucleosides (2'-deoxyguanosine, 2'-deoxyadenosine, or DNA) with N-acetoxy-3-aminobenzanthrone or N-acetyl-N-acetoxy-3-aminobenzanthrone, both of which are recognized as activated metabolites of 3-nitrobenzanthrone. The formation of these multiple DNA adducts may help explain the potent mutacarcinogenicity of 3-nitrobenzanthrone.

Substituent Effects in Benz[a]anthracene Carbocations: A Stable Ion, Electrophilic Substitution (Nitration, Bromination), and DFT Study

A series of novel carbocations were generated from isomeric monoalkylated and dialkylated benz[a]anthracenes (BAs) by low-temperature protonation in FSO(3)H/SO(2)ClF. With the monoalkyl derivatives (5-methyl, 6-methyl, 7-methyl, and 7-ethyl) as well as the D-ring methylated analogues (9-methyl, 10-methyl, and 11-methyl), the C-7 or the C-12 protonated carbocations were observed (as the sole or major carbocation) in all cases. Protonation of the 12-methyl derivative (9) gave the C-7 protonated carbocation (9H+) as the kinetic species and the ipso-protonated carbocation (9aH+) as the thermodynamic cation. With the 12-ethyl derivative (10), relief of steric strain in the bay-region greatly favors ipso-protonation (10aH+). With 3,9-dimethyl (14), C-7 protonation (14H+) is strongly favored (with <10% protonation at C-12), and with 1,12-dimethyl (15) the sole species observed is the C-7 protonated carbocation (15H+). For 7-methyl-12-ethyl, 7-ethyl-12-methyl, and 7,12-diethyl derivatives (16, 17, and 18), two ipso-protonated carbocations were initially formed (C-7/C-12), rearranging in time to give the C-12 protonated carbocations exclusively (16aH+, 17aH+, and 18aH+). Protonation outcomes are compared with the computed relative energies by DFT. Charge delocalization paths in the resulting carbocations were deduced based on the magnitude of Deltadelta13C values. For the thermodynamically more stable C-12 protonated carbocations, the charge delocalization path is analogous to those derived based on computed NPA charges for the benzylic carbocations formed by 1,2-epoxide (bay-region) and 5,6-epoxide (K-region) ring opening. Nitration (and bromination) of the 4-methyl, 7-methyl, 7-ethyl, 3,9-dimethyl, and 1,12-dimethyl derivatives resulted in isolation and characterization of several novel derivatives. Excellent agreement is found between low-temperature protonation selectivities and the regioselectivities observed in model substitution reactions.

Distribution of polycyclic aromatic hydrocarbons in thirty typical soil profiles in the Yangtze River Delta region, east China

Polycyclic aromatic hydrocarbons (PAHs) were quantified in 30 soil profiles from the Yangtze River Delta Region, in east China. Relative concentrations of PAH compounds with different benzene rings and ratios of fluoranthene to fluoranthene plus pyrene and benz(a)anthracene to benz(a)anthracene plus chrysene were used to identify the possible sources of soil PAHs. Total concentrations of 15 PAHs in topsoils ranged from 8.6 to 3881 microg kg(-1) with an average of 397 microg kg(-1). Half of the soil samples were considered to be contaminated with PAHs (>200 microg kg(-1)) and two sampling sites were heavily polluted by PAHs with concentrations >1000 microg kg(-1). Phenanthrene was found in soils below a depth of 100 cm in half of the sampling sites, but the detectable ratio of benzo(a)pyrene decreased sharply from 100% in topsoil to 0 in the 4th horizon.

Iterative benzyne-furan cycloaddition reactions: studies toward the total synthesis of ent-Sch 47554 and ent-Sch 47555

[reaction: see text] 7-Fluoro-5,8-dimethoxy-1-naphthol, prepared from the lithiation and benzyne formation from 1,4-difluoro-2,5-dimethoxybenzene and Diels-Alder cycloaddition with furan, was sequentially C-glycosidated under Suzuki conditions and O-glycosidated using di-O-acetyl-L-rhamnal to provide the corresponding beta-naphthyl C,O-disaccharide. Further lithiation, benzyne formation, and cycloaddition with furan gave an oxa-bridged 1,4-dihydroanthracenyl C,O-disaccharide, a model compound relevant to the total synthesis of Sch 47555.

DNA adduct formation and oxidative stress from the carcinogenic urban air pollutant 3-nitrobenzanthrone and its isomer 2-nitrobenzanthrone, in vitro and in vivo

The carcinogenic vehicle emission product 3-nitrobenzanthrone (3-NBA) is known to rearrange in the atmosphere to the isomer 2-nitrobenzanthrone (2-NBA), which exists in 70-fold higher concentration in ambient air. The genotoxicity of 2-NBA and 3-NBA was studied both in vitro (human cell lines A549 and HepG2) and in vivo (F344 female rats intra-tracheally administered 5 mg/kg body weight of 3-NBA) models, using the (32)P-HPLC and the single-cell gel electrophoresis (Comet assay) methods. In vitro, also the parent compound benzanthrone (BA) and the metabolite 3-aminobenzanthrone (3-ABA) were evaluated. 3-NBA gave highest levels of DNA adducts in the two cell lines, but significantly higher in HepG2 (relative adduct level approximately 500 adducts/10(8) normal nucleotides), whereas 2-NBA formed about one-third and one-twentieth of the DNA adduct amount in A549 and HepG2 cells, respectively. 3-ABA formed only minute amounts of DNA adducts and only in the A549 cells, whereas BA did not give rise to any detectable levels. The DNA adduct patterns from 3-NBA were similar between the two model systems, but differed somewhat for 2-NBA. The oxidative stress induced by BA was almost as high as what was observed for 3-NBA and 3-ABA in both cell lines, and 2-NBA induced lowest level of oxidative stress. The oxidative stress and DNA adduct level, in whole blood, was significantly increased by 3-NBA but not by 2-NBA. However, 2-NBA showed similar toxicity to 3-NBA, with respect to DNA adduct formation in vivo, hence it is important to further study 2-NBA as a potential contributor to health risk. While DNA adduct level in the 3-NBA-exposed animals reached a peak around 1 and 2 days after instillation, 2-NBA-treated animals showed a tendency towards a continuing increase at the end of the study.

Angucyclines Sch 47554 and Sch 47555 from Streptomyces sp. SCC-2136: cloning, sequencing, and characterization

The entire gene cluster involved in the biosynthesis of angucyclines Sch 47554 and Sch 47555 was cloned, sequenced, and characterized. Analysis of the nucleotide sequence of genomic DNA spanning 77.5-kb revealed a total of 55 open reading frames, and the deduced products exhibited strong sequence similarities to type II polyketide synthases, deoxysugar biosynthetic enzymes, and a variety of accessory enzymes. The involvement of this gene cluster in the pathway of Sch 47554 and Sch 47555 was confirmed by genetic inactivation of the aromatase, including a portion of the ketoreductase, which was disrupted by inserting the thiostrepton gene.

Carbocations from oxidized metabolites of benzo[a]anthracene: a computational study of their methylated and fluorinated derivatives and guanine adducts

Structure-reactivity relationships and substituent effects on carbocation stability in benzo[a]anthracene (BA) derivatives have been studied computationally at the B3LYP/6-31G and MP2/6-31G levels. Bay-region carbocations are formed by O-protonation of the 1,2-epoxides in barrierless processes. This process is energetically more favored as compared to carbocation generation via zwitterion formation/O-protonation, via single electron oxidation to generate a radical cation, or via benzylic hydroxylation. Relative carbocation stabilities were determined in the gas phase and in water as solvent (PCM method). Charge delocalization mode in the BA carbocation framework was deduced from NPA-derived changes in charges, and substitution by methyl or fluorine was studied at different positions selected on basis of the carbocation charge density. A bay-region methyl group produces structural distortion with consequent deviation from planarity of the aromatic system, which destabilizes the epoxide, favoring ring opening. Whereas fluorine substitution at sites bearing significant positive charge leads to carbocation stabilization by fluorine p-pi back-bonding, a fluorine atom at a ring position which presented negative charge density leads to inductive destabilization. Methylated derivatives are less sensitive to substituent effects as compared to the fluorinated analogues. Although the solvent decreases the exothermicity of the epoxide ring-opening reactions due to greater stabilization of the reactants, it provokes no changes in relative reactivities. Relative energies in the resulting bay-region carbocations are examined taking into account the available biological activity data on these compounds. In selected cases, quenching of bay-region carbocations was investigated by analyzing relative energies (in the gas phase and in water) and geometries of their guanine adducts formed via covalent bond formation with the exocyclic amino group and with the N-7.

Mutagenic activities and physicochemical properties of selected nitrobenzanthrones

Mutagenic activity of nine nitro derivatives of benzanthrone, namely 1-nitro-, 2-nitro-, 3-nitro-, 9-nitro-, 11-nitro-, 1,9-dinitro-, 3,9-dinitro-, 3,11-dinitro- and 3,9,11-trinitrobenzanthrone were tested with Salmonella strains TA98, TA100, YG1021 and YG1024 in both the presence and absence of an S9 mix. Each compound exhibited mutagenic activity with all the strains. Among these nine isomers, 3-nitrobenzantrone exhibited the most mutagenic activity with all the strains without the S9 mix. The mutagenic activities of the dinitro and trinitro derivatives of benzanthrone were lower than that of the 3-nitro derivative; this is evident from the mutagenic activity of nitrated polyaromatic hydrocarbons (PAH), which is generally enhanced with an increase in nitration. The physicochemical properties of nitrated benzanthrone (reduction potential, hydrophobicity and orientation of nitro groups to the aromatic ring) demonstrated that mononitrated benzanthrone exhibits a lower reduction potential than mononitroPAHs such as 1-nitropyrene and 3-nitrofluoranthene, but was almost equivalent to that of dinitroPAH. Moreover, the mutagenic activity of mononitrobenzanthrones clearly depend on the reduction potential of each compound; however, this tendency was not observed in polynitrobenzanthrones, probably because the reduction of the nitro groups to amino groups of polynitrated benzanthrone might be predominant without a sufficient formation of corresponding hydroxyamines. These results suggest that aromatic compounds that contain keto groups, when nitrated, may act as potentially powerful direct-acting mutagens.

DNA damage and acute toxicity caused by the urban air pollutant 3-nitrobenzanthrone in rats: characterization of DNA adducts in eight different tissues and organs with synthesized standards

3-Nitrobenzanthrone (3-NBA) is an urban air pollutant and rat lung carcinogen that is among the most potent mutagens yet tested in the Salmonella reversion assay. In the present study, 1 mg 3-NBA was administered orally to female F344 rats and DNA adduct formation was examined in liver, lung, kidney and five sections of the gastrointestinal (GI) tract at 6 hr, and 1, 2, 3, 5, and 10 days after administration. The DNA adduct patterns, analyzed by (32)P-postlabelling followed by HPLC separation, were similar in all tissues and organs. Five of the adduct peaks cochromatographed with synthesized DNA adduct standards. Three of these unequivocally determined standards, dGp-C8-N-ABA, dGp-N2-C2-ABA, and dAp-N6-C2-ABA, were of the nonacetylated type, suggesting that at least part of the pathway for activation of 3-NBA proceeds through O-acetylation of the hydroxylamine intermediate. The two other DNA adduct standards, dGp-C8-C2-N-Ac-ABA, and dGp-N2-C2-N-Ac-ABA, were of the acetylated type, but there was some ambiguity in the characterization of these DNA adducts, since they varied inconsistently between samples and they also aligned with peaks found in controls. At 6 hr after treatment, the level of DNA adducts was highest in glandular stomach (relative adduct labeling (RAL), approximately 70 adducts/10(8) normal nucleotides (NN)); adduct levels in this organ decreased at 24 hr, but increased afterwards. DNA adduct levels in the majority of organs were characterized by an early increase (from 6 hr to 3 days), which was followed by a decrease at 5 days and a maximum level 10 days after administration (RAL approximately 120 adducts/10(8) NN for the lung, kidney and glandular stomach, approximately 80 adducts/10(8) NN for the forestomach and ceacum, and approximately 40 adducts/10(8) NN for the liver, small intestine, and colon). This pattern was consistent with pathological observations during autopsy showing high levels of tissue damage in the GI tract; the tissue damage included hemorrhages, loss of villous surface structure in the small intestine, as well as intestine fragility and oedema of the adipose tissue around the GI-tract. Tissue damage decreased and DNA adduct levels increased at 10 days after administration. These observations suggest that 3-NBA not only exerts acute toxic effects, but that the bioavailability is affected by storage in tissues and later becomes available, resulting in the increased DNA adduct levels at the later time points of collection.

Polycyclic aromatic hydrocarbon (PAH) o-quinones produced by the aldo-keto-reductases (AKRs) generate abasic sites, oxidized pyrimidines, and 8-oxo-dGuo via reactive oxygen species

Reactive and redox-active polycyclic aromatic hydrocarbon (PAH) o-quinones produced by Aldo-Keto Reductases (AKRs) have the potential to cause depurinating adducts leading to the formation of abasic sites and oxidative base lesions. The aldehyde reactive probe (ARP) was used to detect these lesions in calf thymus DNA treated with three PAH o-quinones (BP-7,8-dione, 7,12-DMBA-3,4-dione, and BA-3,4-dione) in the absence and presence of redox-cycling conditions. In the absence of redox-cycling, a modest amount of abasic sites were detected indicating the formation of a low level of covalent o-quinone depurinating adducts (>3.2 x 10(6) dNs). In the presence of NADPH and CuCl2, the three PAH o-quinones increased the formation of abasic sites due to ROS-derived lesions destabilizing the N-glycosidic bond. The predominant source of AP sites, however, was revealed by coupling the assay with human 8-oxoguanine glycosylase (hOGG1) treatment, showing that 8-oxo-dGuo was the major lesion caused by PAH o-quinones. The levels of 8-oxo-dGuo formation were independently validated by HPLC-ECD analysis. Apyrimidinic sites were also revealed by coupling the assay with Escherichia coli (Endo III) treatment showing that oxidized pyrimidines were formed, but to a lesser extent. Different mechanisms were responsible for the formation of the oxidative lesions depending on whether Cu(II) or Fe(III) was used in the redox-cycling conditions. In the presence of Cu(II)-mediated PAH o-quinone redox-cycling, catalase completely suppressed the formation of the lesions, but mannitol and sodium benzoate were without effect. By contrast, sodium azide, which acts as a *OH and 1O2 scavenger, inhibited the formation of all oxidative lesions, suggesting that the ROS responsible was 1O2. However, in the presence of Fe(III)-mediated PAH o-quinone redox-cycling, the *OH radical scavengers and sodium azide consistently attenuated their formation, indicating that the ROS responsible was *OH.

Competitive sorption of pyrene on wood chars

Sorption isotherms of pyrene on original and heat-treated wood chars were examined to understand its sorption behavior. Pyrene in single-solute systems had nonlinear isotherms. Polanyi-based dual-domain model fit sorption data well, and the model results showed that the adsorption component dominated pyrene sorption by original char at all aqueous concentrations. In contrast, this adsorption component contributed a much lower fraction to the total sorption by the heat-treated char, and dominated only at low solute concentrations; with increasing concentration, partitioning became a predominant contributor to the total sorption. Competitive effect of four cosolutes, phenanthrene (Phen), benzo[a]anthracene (BaA), 2,2-methylene-bis (4-methyl-6-tert-butylphenol) (MMBP), and phenol on pyrene sorption by original and treated chars was examined to understand the underlying mechanism of competition. Hydrophobicity (adsorbability) and molecular size of competitors played an important role in competition with pyrene by both chars, suggesting the direct competition for sorption sites and pore blockage mechanism. Competitive sorption results indicated that the fate and transport of hydrophobic organic chemicals (e.g., pyrene) could be strongly affected in the presence of coexisting organic contaminants with high hydrophobicity and large molecularsize,thereby, enhancing the mobility and leachability of these chemicals.

Identification of three major DNA adducts formed by the carcinogenic air pollutant 3-nitrobenzanthrone in rat lung at the C8 and N2 position of guanine and at the N6 position of adenine

3-Nitrobenzanthrone (3-NBA) is a potent mutagen and potential human carcinogen identified in diesel exhaust and ambient air particulate matter. Previously, we detected the formation of 3-NBA-derived DNA adducts in rodent tissues by 32P-postlabeling, all of which are derived from reductive metabolites of 3-NBA bound to purine bases, but structural identification of these adducts has not yet been reported. We have now prepared 3-NBA-derived DNA adduct standards for 32P-postlabeling by reacting N-acetoxy-3-aminobenzanthrone (N-Aco-ABA) with purine nucleotides. Three deoxyguanosine (dG) adducts have been characterised as N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-C8-N-ABA), 2-(2'-deoxyguanosin-N2-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-N2-ABA) and 2-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone-3'-phosphate (dG3'p-C8-C2-ABA), and a deoxyadenosine (dA) adduct was characterised as 2-(2'-deoxyadenosin-N6-yl)-3-aminobenzanthrone-3'-phosphate (dA3'p-N6-ABA). 3-NBA-derived DNA adducts formed experimentally in vivo and in vitro were compared with the chemically synthesised adducts. The major 3-NBA-derived DNA adduct formed in rat lung cochromatographed with dG3'p-N2-ABA in two independent systems (thin layer and high-performance liquid chromatography). This is also the major adduct formed in tissue of rats or mice treated with 3-aminobenzanthrone (3-ABA), the major human metabolite of 3-NBA. Similarly, dG3'p-C8-N-ABA and dA3'p-N6-ABA cochromatographed with two other adducts formed in various organs of rats or mice treated either with 3-NBA or 3-ABA, whereas dG3'p-C8-C2-ABA did not cochromatograph with any of the adducts found in vivo. Utilizing different enzymatic systems in vitro, including human hepatic microsomes and cytosols, and purified and recombinant enzymes, we found that a variety of enzymes [NAD(P)H:quinone oxidoreductase, xanthine oxidase, NADPH:cytochrome P450 oxidoreductase, cytochrome P450s 1A1 and 1A2, N,O-acetyltransferases 1 and 2, sulfotransferases 1A1 and 1A2, and myeloperoxidase] are able to catalyse the formation of 2-(2'-deoxyguanosin-N2-yl)-3-aminobenzanthrone, N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone and 2-(2'-deoxyadenosin-N6-yl)-3-aminobenzanthrone in DNA, after incubation with 3-NBA and/or 3-ABA.

An Unusual Reaction of the Natural Compound Benaphthamycin B: Theoretical Study of a Model System

The surprising and complex transformation of benaphthamycin B to give quinone 2a is investigated theoretically with a model compound, 1,5-dihydroxy-4-methoxy-2,3-dimethylanthraquinone (3). The detailed study is performed using both DFT and perturbation theory under inclusion of solvent effects. Several individual steps (reduction and hydrolysis, water elimination, ether cleavage, and oxidation) of the proposed reaction cascade calculated at the PCM-MP2/6-31G(d)//B3LYP/6-31G(d) level of theory are presented and discussed. It is shown that the key step, the ether cleavage as an S(N)2 reaction leading to the anthrone 12a, possesses a smaller activation barrier compared to the alternative process yielding 12b. Therefore, the formation of the thermodynamically preferred model quinone 13a is also the kinetically favored pathway: The results of the calculated model reaction should also be valid for benaphthamycin B (1).

Spectral image adaptation and visual experience of DBA/PMMA

High resolution S0-->Sn and T1-->Tn electronic absorptions and B-type delayed fluorescence of 1,2,7,8-dibenzanthracene in polymethylmethacrylate (PMMA) were experimentally observed by flash and laser flash photolysis technique. Dibenzanthracene (hereafter DBA) molecules were excited in a two-step process. In the first step, an excited singlet is created, which undergoes intersystem crossing to triplet state, then T-T absorption creates an excited triplet dibenzanthracene molecule, which returns to the first excited singlet level by intersystem crossing. The re-created first excited singlet of dibenzanthracene decays back to the ground state by emitting B-type of delayed fluorescence, which was observed at the same emission band of prompt (normal) fluorescence, and R-, E-, P-types of delayed fluorescences. For normal fluorescence, S1 state is decaying to S0 ground state. For E- and P-type of delayed fluorescences, T1 state is decaying to S0 via S1 state, and for B-type of delayed fluorescence, T2 state is decaying to S0 via S1 state. The spectrum image showing the absorption/emission bands mentioned was also examined by image processing techniques in order to improve the visual experience of each band by localizing to a specific region of interest (ROI). Experimental results illustrate how the exact location of emission/absorption bands was clearly extracted from the spectral image and further improvements in the visual detection of absorption/emission bands.

3-Nitrobenzanthrone, a potential human cancer hazard in diesel exhaust and urban air pollution: a review of the evidence

Epidemiological studies have shown that exposure to diesel exhaust and urban air pollution is associated with an increased risk of lung cancer. 3-Nitrobenzanthrone [3-nitro-7H-benz[de]anthracen-7-one (3-NBA)] is an extremely potent mutagen and suspected human carcinogen identified in diesel exhaust and ambient air particulate matter. The main metabolite of 3-NBA, 3-aminobenzanthrone (3-ABA), was found in the urine of salt mine workers occupationally exposed to diesel emissions, indicating that human exposure to 3-NBA due to diesel emissions can be significant and is detectable. There is clear evidence that 3-NBA is a genotoxic mutagen forming DNA adducts after metabolic activation through simple reduction of the nitro group. Several human enzymes have been shown to activate 3-NBA and its metabolites in vitro and in cells to form electrophilic arylnitrenium and rearranged carbenium ions, leading to the formation of purine adducts at the C8 and N2 position of guanine and at the C8 and N6 position of adenine. The predominant DNA adducts in vivo, 2-(2'-deoxyguanosin-N2-yl)-3-aminobenzanthrone and N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone are also the most persistent adducts in target tissue in rodents, and are most probably responsible for the induction of GC-->TA transversion mutations observed in vivo. It is concluded that these adducts not only represent premutagenic lesions in DNA but are of primary importance for the initiation of the carcinogenic process and subsequent tumour formation in target tissue. Indeed, 3-NBA is carcinogenic in rats after intratracheal instillation, inducing mainly squamous cell carcinoma in lung. The intention of this article is to provide a critical review on the potential genotoxic effects of 3-NBA on human health. However, in general, there is a need for more mechanistic studies that relate 3-NBA to all processes that are considered to orchestrate tumour development and of studies on the ability of particles to promote 3-NBA genotoxicity. Because of its widespread environmental presence, 3-NBA may represent not only an occupational health hazard but also a hazard for larger sections of the general population. For an accurate risk assessment more epidemiological studies on 3-NBA-exposed individuals and a broader monitoring of environmental levels of 3-NBA are required.

Synthesis, characterization, and 32p-postlabeling analysis of DNA adducts derived from the environmental contaminant 3-nitrobenzanthrone

3-Nitrobenzanthrone (3-NBA) is a potent mutagen and potential human carcinogen identified in diesel exhaust and ambient air particulate matter. 3-NBA forms DNA adducts in rodent tissues that arise principally through reduction to N-hydroxy-3-aminobenzanthrone (N-OH-ABA), esterification to its acetate or sulfate ester, and reaction of this activated ester with DNA. We detected 3-NBA-derived DNA adducts in rodent tissues by (32)P-postlabeling and generated them chemically by acid-catalyzed reaction of N-OH-ABA with DNA, but their structural identification has not yet been reported. We have now prepared 3-NBA-derived adducts by reaction of a possible reactive metabolite, N-acetoxy-N-acetyl-3-aminobenzanthrone (N-Aco-N-Ac-ABA), with purine nucleosides and nucleotides, characterized them, and have shown that they are present in DNA treated with this 3-NBA derivative. Three of these adducts have been characterized as the C-C adduct N-acetyl-3-amino-2-(2'-deoxyguanosin-8-yl)benzanthrone, the C-N adduct N-acetyl-N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone, and an unusual 3-acetylaminobenzanthrone adduct of deoxyadenosine, which involves a double linkage between adenine and benzanthrone (N1 to C1, N(6) to C11b), creating a five-membered imidazo type ring system. According to IUPAC fused ring conventions, we propose the following systematic name for this adduct: (9'-(2' '-deoxyribofuranosyl))purino[6',1':2,3]imidazo[5,4-p](1,11b-dihydro-(N-acetyl-3-amino))benzanthrone. The 3'-phosphates of these novel adducts could be 5'-postlabeled using [gamma-(32)P]ATP, although the efficiency of labeling was found to be low (less than 20%). However, none of these adducts could be detected in DNA from 3-NBA-treated rats by (32)P-postlabeling. Two of these synthetic adducts were treated with alkali to generate nonacetylated adducts, and these were also shown by HPLC to differ from those adducts found in rat DNA. Therefore, a different approach to the synthesis of authentic standards is needed for the structural characterization of 3-NBA-derived DNA adducts formed in vivo.

Assessment of 3-nitrobenzanthrone reductase activity in mammalian tissues by normal-phase HPLC with fluorescence detection

3-Nitrobenzanthrone (3-NBA) is a potent mutagen and possible human carcinogen present in diesel exhaust and airborne particulate matter. Nitroreduction is believed to play a crucial role in nitroarene activation and mutagenicity; however, quantification of nitroreduction rate in mammalian samples has proved difficult. In this study, we present a sensitive method to quantify 3-nitrobenzanthrone reductase activity in murine tissues via normal-phase HPLC with fluorescence detection of the reduced product 3-aminobenzanthrone (3-ABA). Calibration linearity was obtained for pure 3-ABA concentrations of 1-500 ng/ml (r2>0.99), with a detection limit of 0.25 ng/ml (S/N=3). Incubation time, substrate concentration, and protein concentration in the reaction mixture were optimized, and the detection limit of the enzyme assay is 0.97 pmol/min/mg protein. The apparent K(m) and V(max) for post-mitochondrial supernatant from Mutatrade markMouse liver (i.e., liver S9) were 23.9 microM and 70.2 pmol/min/mg protein, respectively. Analysis of replicate samples of Mutatrade markMouse liver and lung S9 yielded mean activity values of 39.0+/-3.0 and 61.1+/-4.3 pmol/min/mg, respectively. ANOVA revealed significant effects of tissue type and incubation condition (i.e., with or without N2). The results show significantly higher activity in lung, and, in contrast to that observed for 1-nitropyrene, incubation in open air (i.e., without N2 bubbling) causes only a marginal decrease in activity. Quantification of 3-NBA nitroreductase activity in murine tissues will provide insight into the published tissue-specific mutagenic activity of 3-NBA.

LanGT2 Catalyzes the First Glycosylation Step during Landomycin A Biosynthesis

The glycosyltransferase LanGT2 is involved in the biosynthesis of the hexasaccharide side chain of the angucyclic antibiotic landomycin A. Its function was elucidated by targeted gene inactivation of lanGT2. The main metabolite of the obtained mutant was identified as tetrangulol (4), the progenitor of the landomycin aglycon (7). The lack of the sugar side chain indicates that LanGT2 catalyzes the priming glycosyl transfer in the hexasaccharide biosynthesis: the attachment of a D-olivose to O-8 of the polyketide backbone. Heterologous expression of urdGT2 from S. fradiae Tü2717 in this mutant resulted in the production of a novel C-glycosylated angucycline (6).

Degradation of benz[a]anthracene by Mycobacterium vanbaalenii strain PYR-1

Cultures of Mycobacterium vanbaalenii strain PYR-1 grown in mineral salts medium and nutrients in the presence of benz[a]anthracene metabolized 15% of the added benz[a]anthracene after 12 days of incubation. Neutral and acidic ethyl acetate extractable metabolites were isolated and characterized by high performance liquid chromatography (HPLC) and uv-visible absorption, gas chromatography/mass (GC/MS) and nuclear magnetic resonance (NMR) spectral analysis. Trimethylsilylation of the metabolites followed by GC/MS analysis facilitated identification of metabolites. The characterization of metabolites indicated that M. vanbaalenii initiated attack of benz[a]anthracene at the C-1,2-, C-5,6-, C-7,12- and C-10,11-positions to form dihydroxylated and methoxylated intermediates. The major site of enzymatic attack was in the C-10, C-11 positions. Subsequent ortho- and meta-cleavage of each of the aromatic rings led to the accumulation of novel ring-fission metabolites in the medium. The major metabolites identified were 3-hydrobenzo[f]isobenzofuran-1-one (3.2%), 6-hydrofuran[3,4-g]chromene-2,8-dione (1.3%), benzo[g]chromene-2-one (1.7%), naphtho[2,1-g]chromen-10-one (48.1%), 10-hydroxy-11-methoxybenz[a]anthracene (9.3%), and 10,11-dimethoxybenz[a]anthracene (36.4%). Enzymatic attack at the C-7 and C-12 positions resulted in the formation of benz[a]anthracene-7,12-dione, 1-(2-hydroxybenzoyl)-2-naphthoic acid, and 1-benzoyl-2-naphthoic acid. A phenyl-naphthyl metabolite, 3-(2-carboxylphenyl)-2-naphthoic acid, was formed when M. vanbaalenii was incubated with benz[a]anthracene cis-5,6-dihydrodiol, indicating ortho-cleavage of 5,6-dihydroxybenz[a]anthracene. A minor amount of 5,6-dimethoxybenz[a]anthracene was also formed. The data extend and propose novel pathways for the bacterial metabolism of benz[a]anthracene.

Fluorescent Characteristics of Rheumatoid Arthritis Patients Blood Lymphocytes

A fluorescent probe, ABM, aminoderivative of benzanthrone, synthesized in the Department of Organic Chemistry of the Riga Technical University (Latvia), has been successfully used to characterize changes in the structural and functional properties of cell membranes during different pathologies. In the present study the physicochemical properties and the functional activity of the peripheral blood mononuclear cells (lymphocytes-Ly) in patients with rheumatoid arthritis (RA) were studied using the ABM probe. Intensity of the ABM fluorescence in the celi suspension, functional activity of the ly anisotropy of the membranes differ patients with different titres of rheumatoid factor in blood. Patients with seropositive RA had decreased proliferative activity and lower number of iy in blood plasma indicating greater alterations of the immunoregulating processes in these patients as compared to patients with seronegative RA. In the latter the Ly deficiency is compensated to some extent by increased proliferation activity of these cells. The ABM fluorescence intensity correlated not only with membrane anisotropy (r = 0.97, but also with the proliferation activity of the Ly (r = 0.98). The above parameters correlated with the clinical manifestations of the disease. The results indicate that the fluorescent probe ABM is useful for screening the physicochemical status of Ly membranes and the proliferation activity of these cells in RA patients.

Altered expression of anti and proapoptotic proteins during chemoprevention of hamster buccal pouch carcinogenesis by tomato and garlic combination

BACKGROUND

Effective combinations of dietary agents are promising candidates for cancer chemoprevention because of their safety and the fact that they are not perceived as medicine. The present study was designed to investigate the apoptosis-inducing effect of combined administration of tomato and garlic during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis.

METHODS

Hamsters were divided into four groups. The right buccal pouches of animals in group 1 were painted with 0.5% DMBA three times a week. Animals in group 2 painted with DMBA as in group 1, received in addition intragastric administration of a combined dose of tomato and garlic on days alternate to DMBA application. Group 3 animals were given chemopreventive agents alone. Animals in group 4 served as control. All the animals were sacrificed after an experimental period of 14 weeks. DNA fragmentation and the apoptosis-associated proteins-Bcl-2, Bax, Bim, P53 as well as caspases 8 and 3 were used as markers of apoptosis.

RESULTS

Topical application of DMBA for 14 weeks resulted in well-developed squamous cell carcinomas (SCCs) associated with increased expression of Bcl-2 and decreased expression of Bax, Bim, P53 and caspases 8 and 3. Combined administration of tomato and garlic significantly inhibited the development of HBP carcinomas and induced apoptosis. This was evidenced by downregulation of Bcl-2 and upregulation of Bax, Bim, P53 and caspases 8 and 3.

CONCLUSION

The induction of apoptosis may be one of the mechanisms through which functional foods such as tomato and garlic exert their anticancer properties.

Highly sensitive detection of discrete absorption and B-type delayed fluorescence of dibenzanthracene in PMMA

High resolution S0 --> Sn and T1 --> Tn electronic absorptions and B-type delayed fluorescence of 1,2,7,8-dibenzanthracene in polymethylmethacrylate (PMMA) were experimentally observed by flash and laser flash photolysis technique. Dibenzanthracene molecules were excited in a two-step process. In the first step, an excited singlet is created, which undergoes intersystem crossing to triplet state, then T-T absorption creates an excited triplet dibenzanthracene molecule, which returns to the first excited singlet level by intersystem crossing. The re-created first excited singlet of dibenzanthracene decays back to the ground state by emitting B-type of delayed fluorescence, which was observed at the same emission band of prompt (normal) fluorescence, and R-, E-, P-types of delayed fluorescences. For normal fluorescence, S1 state is decaying to S0 ground state. For E- and P-type of delayed fluorescences, T1 state is decaying to S0 via S1 state, and for B-type of delayed fluorescence, T2 state is decaying to S0 via S1 state.

Oxidative DNA Damage Induced by Benz[a]anthracene Dihydrodiols in the Presence of Dihydrodiol Dehydrogenase

Tobacco smoke and polluted air are risk factors for lung cancer and contain many kinds of polycyclic aromatic hydrocarbons (PAHs) including benzo[a]pyrene (B[a]P) and benz[a]anthracene (BA). BA, as well as B[a]P, is assessed as probably carcinogenic to humans (IARC group 2A). BA is metabolized to several dihydrodiols. Dihydrodiol dehydrogenase (DD), a member of the aldo-keto reductase superfamily, catalyzes NAD(P)+-linked oxidation of dihydrodiols of aromatic hydrocarbons to corresponding catechols. To clarify the role of DD on PAH carcinogenesis, we examined oxidative DNA damage induced by trans-dihydrodiols of BA and B[a]P treated with DD using 32P-5'-end-labeled DNA fragments obtained from the human p53 tumor suppressor gene. In addition, we investigated the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), an indicator of oxidative DNA damage, in calf thymus DNA by using HPLC with an electrochemical detector. DD-catalyzed BA-1,2-dihydrodiol caused Cu(II)-mediated DNA damage including 8-oxodG formation in the presence of NAD+. BA-1,2-dihydrodiol induced a Fpg sensitive and piperidine labile G lesion at the 5'-ACG-3' sequence complementary to codon 273 of the human p53 tumor suppressor gene, which is known as a hotspot. DNA damage was inhibited by catalase and bathocuproine, suggesting the involvement of H2O2 and Cu(I). The observation of NADH production by UV-visible spectroscopy suggested that DD catalyzed BA-1,2-dihydrodiol most efficiently to the corresponding catechol among the PAH-dihydrodiols tested. A time-of-flight mass spectroscopic study showed that the catechol form of BA-1,2-dihydrodiol formed after DD treatment. In conclusion, BA-1,2-dihydrodiol can induce DNA damage more efficiently than B[a]P-7,8-dihydrodiol and other BA-dihydrodiols in the presence of DD. The reaction mechanism on oxidative DNA damage may be explained by theoretical calculations with an enthalpy change of dihydrodiols and oxidation potential of their catechol forms. DD may play an important role in BA carcinogenesis via oxidative DNA damage.

Synthesis of the o-quinones and other oxidized metabolites of polycyclic aromatic hydrocarbons implicated in carcinogenesis

Efficient new syntheses of the o-quinone derivatives of benzo[a]pyrene (BPQ), 7,12-dimethylbenz[a]anthracene (DMBAQ), and benz[a]anthracene (BAQ), implicated as active carcinogenic metabolites of the parent polycyclic aromatic hydrocarbons (PAHs), are reported. These PAH quinones also serve as starting compounds for the synthesis of the other active metabolites of these PAHs thought to be involved in their mechanism(s) of carcinogenesis. The latter include the corresponding o-catechols, trans-dihydrodiols, and the corresponding anti- and syn-diol epoxides.

Metabolism of the polynuclear sulfur heterocycle benzo[b]phenanthro[2,3-d]thiophene by rodent liver microsomes: evidence for multiple pathways in the bioactivation of benzo[b]phenanthro[2,3-d]thiophene

Benzo[b]phenanthro[2,3-d]thiophene (BPT), a thia analogue of dibenz[a,h]anthracene (DBA), is a carcinogenic environmental pollutant. We have examined the metabolism of BPT by rodent liver microsomes to investigate the mechanism by which BPT produces mutagenic and carcinogenic effects. Both rat and mouse liver microsomes biotransformed [G-(3)H]BPT to various metabolites including BPT 3,4-diol and BPT sulfoxide, which are significantly more mutagenic than the parent compound. Liver microsomes from both control mice and rats metabolize BPT at similar rates. Treatment of mice with P450 inducers DBA, 3-methylcholanthrene (3-MC), Aroclor 1254, and phenobarbital enhanced the rate of metabolism of BPT by 74-, 28-, 77-, and 6-fold, respectively. In comparison, the treatment of rats with DBA and 3-MC increased the rate of metabolism of BPT by 22- and 34-fold, respectively, suggesting that P450 enzymes responsible for the metabolism of BPT are enhanced to different extents in rats and mice by a similar class of compounds. In general, the liver microsomes from mice treated with DBA or 3-MC were more active than those from similarly treated rats in metabolizing BPT to its 3,4-diol, a precursor to the bay-region diol epoxide of BPT. BPT sulfone was a minor metabolite (if formed) in all cases. The liver microsomes from rats treated with DBA or 3-MC or from mice treated with PB produced a significant proportion of BPT sulfoxide (12-41%). In contrast, the liver microsomes from DBA- or 3-MC-treated mice formed BPT sulfoxide as a minor metabolite (<2%). These studies indicate that cytochrome P450 enzymes induced by PAHs (e.g., P450 1A1 and P450 1B1) and by PB (e.g., P450 2B1, 3A1, and/or 3A2) are involved in the metabolism of BPT to mutagenic BPT 3,4-diol and BPT sulfoxide, providing evidence for the first time that BPT and possibly other thia-PAHs are metabolically activated via the formation of both the dihydrodiol (and subsequently diol epoxide) and the sulfoxide.

Transport of anthracene and benz(a)anthracene through iron-quartz and three aquifer materials in laboratory columns

In groundwater systems, dissolved natural organic matter (NOM) can influence the mobility of organic contaminants by altering the contaminant behavior in water and solid phases. The transport of anthracene and benz(a)anthracene (B(a)A) was studied in the presence and absence of NOM and/or soil organic matter (SOM) in column experiments. The results show that sorption are related to the properties of polycyclic aromatic hydrocarbons (PAHs), NOM and SOM. In the Fe-quartz media, the amount of NOM (20 mg/l) in solution had a little effect on increasing the apparent solubility of anthracene and countering increased anthracene sorption. In the natural (Bemidji) soil, Suwannee river fulvic acid (SRFA, 20 mg/l) and Suwannee river humic acid (SRHA) in water did not compete with SOM for anthracene, indicating that SOM has higher partition efficiency for anthracene. It was also observed that slow diffusion through an organic phase apparently caused most of the observed tailing in column breakthrough curves (BTCs). Even though the fOC of washed Bemidji sediment was very low, the transport of B(a)A was retarded significantly, however, and the transport of B(a)A was shown to be facilitated by dissolved NOM.

Seitomycin: isolation, structure elucidation and biological activity of a new angucycline antibiotic from a terrestrial Streptomycete

A new antibiotic, named seitomycin (1c), and the known microbial metabolite tetrangulol methyl ether (2) were found in the ethyl acetate extract of two terrestrial Streptomyces sp. isolates. The structure of the new antibiotic was elucidated by spectroscopic studies and by comparison of the NMR data with the structurally related hatomarubigin C (1a) and SM-196 B (1b). Seitomycin (1c) showed moderate antimicrobial and weak phytotoxic activity, similar to tetrangulol methyl ether (2).

Cytochrome c location in phosphatidylcholine/cardiolipin model membranes: resonance energy transfer study

Resonance energy transfer between lipid-bound fluorescent probe 3-methoxybenzanthrone as a donor and heme group of cytochrome c as an acceptor has been examined to ascertain the protein disposition relative to the surface of model membranes composed of phosphatidylcholine and cardiolipin (10, 50 and 80 mol%). The model of energy transfer in membrane systems has been extended to the case of donors distributed between the two-bilayer leaflets and acceptors located at the outer monolayer taking into account the donor and acceptor orientational behavior. Assuming specific protein orientation relative to the membrane surface and varying lateral distance of the donor-acceptor closest approach in the range from 0 to 3.5 nm the limits for possible heme distances from the bilayer midplane have been found to be 0.8-3 nm (10 mol% CL), 0-2.6 nm (50 mol% CL), and 1.4-3.3 nm (80 mol% CL).