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HPLC-(1)H NMR has been used to study the tissue-specific distribution of phenylphenalenones, polyphenolic natural products of Xiphidium caeruleum, a neotropical member of the Haemodoraceae plant family. The present results provide insight into the occurrence of phenylphenalenone-related compounds in root segments of whole plants and different in vitro culture lines of the same species.
This paper presents calculations of the NICS (nuclear independent chemical shieldings) in a rectangular grid surrounding the molecules of benzene, naphthalene and coronene. Using the relationship between calculated NICS and the induced magnetic field, the calculated NICS are used to predict intermolecular effects due to molecular magnetic susceptibility or ring current effects. As expected from approximate ring current models, these intermolecular shielding effects are concentrated along the direction perpendicular to the molecular plane and they approach asymptotically to a dipolar functional dependence, i.e. (1-3 cos(2)theta)/r(3)). The deviations from the dipolar functional form require that the calculations of these intermolecular effects be done using a suitable interpolation scheme of the NICS calculated on the grid. The analysis of the NICS tensor components shows that these intermolecular shielding effects should be primarily expected on shielding components of the neighboring molecules nuclei, which are perpendicular to the molecular plane of the aromatic compound generating the induced field. The analysis of the calculated NICS along the series benzene, naphthalene and coronene shows that these intermolecular effects increase monotonically with the number of aromatic rings.
The products of aqueous chlorination reactions of tricyclic aromatic hydrocarbons (fluorene, carbazole, dibenzofuran, anthracene, phenanthrene and some methyl derivatives) with hypochlorite have been determined by gas chromatography-mass spectrometry. They included chloro-substituted, oxygenated (quinones) and hydroxylated (phenols) compounds, and products of addition which were readily formed at ambient temperature. The extent of the reactions was shown to depend on the chlorine dose, the solution pH, the initial concentrations of both compounds and the structures. Monochlorinated compounds and quinones were shown to be present in chlorinated water under the conditions utilized for water treatment.
Three fused octacyclic phenylphenalenone dimers were isolated from Musa acuminata: Anigorootin, which was first isolated from Anigozanthos flavidus and hitherto represented the only compound of that type, the new 4'-hydroxy-anigorootin, and 4',4"-di-hydroxy-anigorootin, which is a revised structure. The crystal structure of anigorootin was determined by X-ray crystallography. 3,3'-Bis-hydroxyanigorufone, a dimer of the conventional type known from Anigozanthos preissii, was also found in Musa acuminata. Phytochemical analysis of several Haemodoraceae species revealed the occurrence of anigorootin, 3,3'-bis-hydroxyanigorufone, and the novel metabolite 3,3'-bis-anigorufone. The occurrence of the same compounds in Musaceae and Haemodoraceae indicates the close chemotaxonomic relationship of both plant families.
A new type of fiber-optic chemical sensor has been developed for the determination and differentiation of geometric isomers. The operation of the sensor is based upon the molecular-geometric-selective absorption of polynuclear aromatic hydrocarbons (PAH) on a liquid crystal. The selective interaction of a PAH with a liquid-crystal substrate causes quenching of the liquid-crystal fluorescence. Detection limits of such a device for PAH compounds approach 10(-10) mol/cm3; the sensor response time is about 2 min. Because the sensor is based upon physical absorption, it is reusable and reversible.
The total synthesis of 1-O-methyllateriflorone (2) is described. The construction of the cage-like domain of the molecule involved a biomimetic Claisen/Diels-Alder cascade, whereas the novel spiroxalactone framework was generated by an intramolecular Michael reaction within precursor 16a involving the carboxylate residue as the nucleophile. This finding might bear on the biosynthetic pathway by which nature forms lateriflorone. Described herein is also an interesting cascade sequence involving facile 6 pi electrocyclizations which leads to complex benzopyran systems. The biological evaluation of a small library of lateriflorone analogues and related systems establishing the first SAR within this class of compounds is also included. Among the most active compounds against tumor cells are 2, 16b, 56, 58, and 59.
Radioactive carcinogens have provided most of our present knowledge about the interactions between carcinogens and components of biological systems. The requirement of radioactive carcinogens restricts carcinogen-DNA binding studies to chemicals that are readily available in isotopically labelled form, i.e., a minute fraction of all potentially mutagenic or carcinogenic chemicals. To extend the scope of carcinogen-DNA binding studies, an alternative method, which does not require radioactive test chemicals, has been developed. In this approach, radioactivity (32P) is incorporated into DNA constituents by polynucleotide kinase-catalysed (32P)-phosphate transfer from (gamma-32P)ATP after exposure of the DNA, in vitro or in vivo, to a nonradioactive, covalently binding chemical; alteration of DNA nucleotides is shown by the appearance of extra spots on autoradiograms from thin-layer chromatograms of digests of the chemically modified DNA. Adduct levels are quantitated by scintillation counting. The sensitivity of the technique depends, to some extent, on the chemical structure of the adducts, in that greater sensitivity is achieved if adducts can be separated, as a class, from the normal nucleotides. An estimated 80% of all carcinogens can be separated in this way, giving rise to bulky and/or aromatic substituents in DNA. Under present conditions, one such adduct in 10(9)-10(10) normal nucleotides can be detected. A total of 41 compounds has been studied, so far. Binding to DNA of rodent liver and skin was readily detected by the 32P-postlabelling assay for all known carcinogens among these compounds, and adducts were detected in DNA from tissues of smokers.
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The concentrations of a suite of persistent organic chemicals were measured in multiple media in 10 child day care centers located in central North Carolina. Five centers served mainly children from low-income families, as defined by the federal Women, Infants, and Children (WIC) assistance program, and five served mainly children from middle-income families. The targeted chemicals were chosen because of their probable carcinogenicity, acute or chronic toxicity, or hypothesized potential for endocrine system disruption. Targeted compounds included polycyclic aromatic hydrocarbons (PAHs), pentachloro- and nonyl-phenol, bisphenol-A, dibutyl and butylbenzyl phthalate, polychlorinated biphenyls (PCBs), organochlorine pesticides, the organophosphate pesticides diazinon and chlorpyrifos, and the herbicide 2,4-dichlorophenoxyacetic acid (2,4D). Sampled media were indoor and outdoor air, food and beverages, indoor dust, and outdoor play area soil. Concentrations of the targeted compounds were determined using a combination of extraction and analysis methods, depending on the media. Analysis was predominantly by gas chromatography/mass spectrometry (GC/MS) or gas chromatography with electron capture detection (GC/ECD). Concentrations of the targeted pollutants were low and well below the levels generally considered to be of concern as possible health hazards. Potential exposures to the target compounds were estimated from the concentrations in the various media, the children's daily time-activity schedules at day care, and the best currently available estimates of the inhalation rates (8.3 m(3)/day) and soil ingestion rates (100 mg/day) of children ages 3-5. The potential exposures for the target compounds differed depending on the compound class and the sampled media. Potential exposures through dietary ingestion were greater than those through inhalation, which were greater than those through nondietary ingestion, for the total of all PAHs, the phenols, the organophosphate pesticides, and the organochlorine pesticides. Potential exposures through dietary ingestion were greater than those through nondietary ingestion, which were greater than those through inhalation, for those PAHs that are probable human carcinogens (B2 PAH), the phthalate esters, and 2,4D. For the PCBs, exposures through inhalation were greater than those through nondietary ingestion, and exposures through dietary ingestion were smallest. Differences in targeted compound levels between the centers that serve mainly low-income clients and those that serve mainly middle-income clients were small and depended on the compound class and the medium.
Metabolism of chemicals occurs in skin and therefore should be taken into account when one determines topical exposure dose. Skin metabolism is difficult to measure in vivo because biological specimens may also contain metabolites from other tissues. Metabolism in skin during percutaneous absorption can be studied with viable skin in flow-through diffusion cells. Several compounds metabolized by microsomal enzymes in skin (benzo[a]pyrene and 7-ethoxycoumarin) penetrated human and hairless guinea pig skin predominantly unmetabolized. However, compounds containing a primary amino group (p-aminobenzoic acid, benzocaine, and azo color reduction products) were substrates for acetyltransferase activity in skin and were substantially metabolized during absorption. A physiologically based pharmacokinetic model has been developed with an input equation, allowing modeling after topical exposure. Plasma concentrations in the hairless guinea pig were accurately predicted for the model compound, benzoic acid, from in vitro absorption, metabolism, and other pharmacokinetic parameters.
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N-(4-Methoxy-2,3-dihydro-1H-phenalen-2-yl)amide derivatives, conformationally restricted ligands for melatonin receptors, were synthesized by an alternative synthetic method from the corresponding 1,8-naphthalic anhydride which was transformed into the phenalenecarboxylic acid 7. A Curtius reaction on 7 gave the amino compound which was acylated to give compounds 4a-c. The (+)- and (-)-4a-c enantiomers were separated by semipreparative chiral HPLC. Compounds were evaluated for their affinity for chicken brain melatonin receptors in binding assays using 2-[125I]iodomelatonin and for their potency to lighten the skin of Xenopus laevis tadpoles. The butyramido derivative 4c was the most potent ligand (Ki = 1.7 nM). No enantioselectivity was observed with the enantiomers which were equipotent to the racemic mixture. In contrast to the reference compounds, melatonin, agomelatine (S 20098), and N-[2-(2, 7-dimethoxynaphth-1-yl)ethyl]acetamide, which were very potent at lightening the skin of X. laevis tadpoles, compounds 4a-c were inactive or weakly active (EC50 > 1 microM). In this bioassay, compound 4a was characterized as a putative antagonist of melatonin receptors.
Phytochemical analysis of rhizomes of Strelitzia reginae resulted in the isolation and identification of an unusual new (1) and four known phenalenone-type compounds, which were identified using MS and NMR spectroscopic techniques. The occurrence of phenalenones in Strelitziaceae, which has been established for the first time, is of chemotaxonomic interest.
Four blocked mutants which accumulated new dihydrobenzo[a]naphthacenequinone metabolites, designated pradimicins M, N, O and P, have been isolated from cultures of mutants of Actinomadura hibisca P157-2 resulting from treatment with N-methyl-N'-nitro-N-nitrosoguanidine. The structures of the four compounds were determined by spectral analysis. Pradimicins N, O and P contain D-alanine, while pradimicin M does not. The conformations at C-5 and C-6 of these compounds are different from those of the original pradimicins.
The rules of molecular geometry for predicting carcinogenic activity of polynuclear aromatic hydrocarbons (PAH) have been applied to a series of 50 unsubstituted PAH, and predicted carcinogenic activity is in good agreement with the results of testing for complete carcinogenic activity in mice and/or rats. The rules were developed from a knowledge of the center or centers of highest chemical or biochemical reactivity and are consistent with a unified hypothesis which states that the first step in the metabolic activation of unsubstituted PAH is the biochemical introduction of a methyl group. This bioalkylation reaction 1) takes place between certain PAH and S-adenosyl-L-methionine and is catalyzed by cytosolic methyltransferase, 2) offers a means of probing for centers of reactivity in PAH, 3) provides a biochemical link between unsubstituted preprocarcinogens of aromatic type ArX and alkyl-substituted procarcinogens of aromatic type ArCH2X (where X = H), and 4) makes it possible to include compounds of both aromatic types, in a consistent theory of aromatic hydrocarbon activation which incorporates alkyl substitution. The present study reveals that there are structural determinants of carcinogenicity.
This study deals with some methods of making human exposure estimates, aimed at describing the human exposure for selected air pollutants in Sweden that are suspected carcinogens. Nitrogen oxides (NOx) have been chosen as an indicator substance for estimating the concentration of the urban plume. Earlier investigations have shown that the traffic in Swedish cities contributes around 85% to the measured NOx concentrations, and that most of the mutagenicity in urban air originates from traffic. The first section of this paper describes measurements in Stockholm of some unregulated light hydrocarbons, such as ethene, ethyne, propane, propene, butane, and isobutane. In addition, measurements of some volatile aromatic hydrocarbons are presented. Simultaneous measurements of carbon monoxide (CO) were made. The ratios between CO and the individual specific compounds were determined by linear regression analysis. By analysis of relationships between CO and NOx, NOx concentrations can be used as a tracer to describe the exposure for these specific compounds. NOx are considered to be a better tracer than CO, because NOx or NO2 values exist for many places over a long time, while CO is measured mostly in streets with high concentrations. At low concentrations, instruments that measure normal CO levels give no detectable signals. Through use of atmospheric dispersion models and models that describe how people live and work in urban areas it has been possible to describe the average exposure to NOx in cities of different sizes. The exposure to NOx for people living in the countryside has also been estimated. In this way, it has been possible to calculate the average exposure dose for NOx for the Swedish population. This figure is 23 micrograms/m3. By use of the relationships between NOx and specific compounds the average dose has been calculated for the following compounds: polyaromatic compounds (PAH); ethene, propene, and butadiene; benzene, toluene, and xylene; formaldehyde and actaldehyde; nickel, chromium (VI), arsenic, and cadmium; asbestos; and silicon.
Epidemiological and laboratory studies provide insight into the anticarcinogenic potential of garlic and its constituent compounds. Both water- and lipid-soluble allyl sulfur compounds are effective in blocking a myriad of chemically induced tumors. Part of the protection from these compounds probably relates to a block in nitrosamine formation and metabolism. However, blockage in the initiation and promotion phases of the carcinogenicity of various compounds, including polycyclic hydrocarbons, provide evidence that garlic and its constituents can alter several phase I and II enzymes. Their ability to block experimentally induced tumors in a variety of sites including skin, mammary and colon, suggests a general mechanism of action. Changes in DNA repair and in immunocompetence may also account for some of this protection. Some, but not all, allyl sulfur compounds can also effectively retard tumor proliferation and induce apoptosis. Changes in cellular thiol and phosphorylation stains may account for some of these antitumorigenic properties. The anticarcinogenic potential of garlic can be influenced by several dietary components including specific fatty acids, selenium, and vitamin A. Since garlic and its constituents can suppress carcinogen formation, carcinogen bioactivation, and tumor proliferation it is imperative that biomarkers be established to identify which individuals might benefit most and what intakes can occur with ill consequences.