Antimicrobial, Cytotoxic and Mutagenic Activity of Gemini QAS Derivatives of 1,4:3,6-Dianhydro-l-iditol.

A series of quaternary diammonium salts derivatives of 1,4:3,6-dianhydro-l-iditol were synthesized, using isommanide (1,4:3,6-dianhydro-d-mannitol) as a starting material. Both aromatic (pyridine, 4-(N,N-dimethylamino)pyridine (DMAP), (3-carboxamide)pyridine; N-methylimidazole) and aliphatic (trimethylamine, N,N-dimethylhexylamine, N,N-dimethyloctylamine, N,N-dimethyldecylamine) amines were used, giving eight gemini quaternary ammonium salts (QAS). All salts were tested for their antimicrobial activity against yeasts, Candida albicans and Candida glabrata, as well as bacterial Staphylococcus aureus and Escherichia coli reference strains. Moreover, antibacterial activity against 20 isolates of S. aureus collected from patients with skin and soft tissue infections (n = 8) and strains derived from subclinical bovine mastitis milk samples (n = 12) were evaluated. Two QAS with octyl and decyl residues exhibited antimicrobial activity, whereas those with two decyl residues proved to be the most active against the tested pathogens, with MIC of 16-32, 32, and 8 µg/mL for yeast, E. coli, and S. aureus reference and clinical strains, respectively. Only QAS with decyl residues proved to be cytotoxic in MTT assay against human keratinocytes (HaCaT), IC50 12.8 ± 1.2 µg/mL. Ames test was used to assess the mutagenic potential of QAS, and none of them showed mutagenic activity in the concentration range 4-2000 µg/plate.

Applying Bayesian forecasting to predictive toxicology: The probability of innate carcinogenicity to humans of colorants synthesized from benzidine.

The preclinical identification of health hazards relies on the performance (the historic concordance to the respective gold standard) of regulatorily recommended bioassays. However, any testing with less than 100% sensitivity (or 100% specificity) can deliver false results (outcomes discordant to the respective gold standard). Conversely, the predictive values approach (a.k.a. Bayesian forecasting) weighs (1) the performance of the predictive bioassay (battery, or framework) with (2) the prevalence of -positivity to the respective gold standard- in the most representative category to which the test substance can be allocated. Thus, the predictive values approach (PVA) provides the numeric probability for the toxicity to humans of chemicals that, circumstantially, are evaluable only through nonclinical data. Consequently, the PVA improves the predictivity of nonclinical toxicology, and increases the impact of hazard identifications entirely based on preclinical data. This article aimed to introduce the PVA through a worked example. Due to their toxicological homogeneity and public health relevance, the superfamily of colorants synthesized from benzidine (BZ) or some mutagenic congeners was selected (colorings hereafter mentioned as BZ-related-colorants). Through the PVA, the numeric probability of innate carcinogenicity to humans of 259 BZ-related-colorants was either estimated from rodent carcinogenesis bioassays (RCBs) or predicted from methods alternative to the RCB. A discussion was provided on (1) some limitations and implications of the PVA, and (2) the probable significance of the predictive values figured here for 259 BZ-related-colorings.

Synthesis of silver nanoparticles using Ziziphus nummularia leaf extract and evaluation of their antimicrobial, antioxidant, cytotoxic and genotoxic potential (4-in-1 system).

This study reports the synthesis of silver nanoparticles (AgNPs) from silver nitrate by leaf extract of a medicinal plant Ziziphus nummularia. The leaf extract acts as a reducing and stabilizing agent for the formation of nanoparticles. The green synthesized AgNPs were characterized by ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FITR) spectroscopy, Thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM) analysis and evaluated their antimicrobial, antioxidant, cytotoxic and genotoxic potential. The UV-Vis spectroscopy showed a characteristic absorption peak at 430 nm due to surface plasma resonance. TEM analysis showed that synthesized AgNPs were spherical and oval with an average size of 25.96 nm. AgNPs showed effective antimicrobial activity (lowest MIC-0.625 µg/mL against Escherichia coli), synergistic antimicrobial activity (lowest ΣFIC 0.09 with chlormaphenicol against Corynebacterium rubrum) and antibiofilm activity. AgNPs showed strong DPPH activity with IC50 - 520 µg/mL and ABTS activity IC50 - 55 µg/mL and reducing capacity assessment. In vitro cytotoxic effect was evaluated by MTT assay against HeLa cells, breast cells and fibroblast cells. Genotoxic effect was evaluated by comet assay. AgNPs displayed dose-dependent cytotoxic and genotoxic effect. Our findings indicated that synthesized AgNPs could be considered as multifunctional and have great potential for use in biomedical applications.HighlightsSilver nanoparticles were synthesized using leaf extract of Ziziphus nummulariaCharacterization was done by various spectral techniquesAntimicrobial efficacy was demonstrated against an array of bacteriaAgNPs exhibited significant cytotoxic effect against HeLa cell lineAgNPs showed cytotoxicity and genotoxicity in a dose-dependent manner.

Copper(I) complexes with phosphines P(p-OCH3-Ph)2CH2OH and P(p-OCH3-Ph)2CH2SarGly. Synthesis, multimodal DNA interactions, and prooxidative and in vitro antiproliferative activity.

Phosphonium salt (p-OCH3-Ph)2P(CH2OH)2Cl (MPOHC), derived phosphine ligands without and with SarGly (Sarcosine-Glycine) peptide carrier P(p-OCH3-Ph)2CH2OH (MPOH) and P(p-OCH3-Ph)2CH2SarGly (MPSG), respectively, and two copper(I) complexes [Cu(I)(dmp)(MPOH)] (1-MPOH; dmp = (2,9-dimethyl-1,10-phenanthroline)) and [Cu(I)(dmp)(MPSG)] (1-MPSG) were synthesized. The resulting compounds were characterized by elemental analysis, 1D and 2D NMR and UV-Vis absorption spectroscopies, mass spectrometry, cyclic voltammetry and by X-ray diffraction analysis. Cytotoxicity of all compounds was evaluated in vitro against colon, lung, breast, pancreatic, prostate tumor cell lines, as well as towards non-tumor cell lines: lung, kidney and keratinocyte. Stable in biological medium in the presence of atmospheric oxygen, Cu(I) complexes exerted a cytotoxic effect higher than that elicited by cisplatin against tested cancer cell lines. The introduction of methoxy group onto the phenyl rings of the phosphine ligand coordinated to the copper(I) ion resulted in a relevant increase of cytotoxicity in the case of breast, pancreatic and prostate tumor cell lines in vitro. Attachment of a peptide carrier significantly increased the selectivity towards cancer cells. Fluorescence spectroscopic data (calf thymus DNA: CT-DNA) titration), together with analysis of DNA fragmentation (gel electrophoresis) and molecular docking provided evidence for the multimodal interaction of copper compounds with DNA and showed their unusual low genotoxicity. Additionally, copper complexes were able to generate reactive oxygen species as a result of redox processes, proved by fluorescence spectroscopy and cyclic voltamperometry.

Synthesis, Characterization and Biological Application of Pyrazolo[1,5-a]pyrimidine Based Organometallic Re(I) Complexes.

The neutral rhenium(I) complexes (I-VI) of type [ReCl(CO)3Ln-] where L1 = 7-phenyl-5-(pyridin-2-yl)pyrazolo[1,5-a]pyrimidine, L2 = 7-(4-bromophenyl)-5-(pyridin-2-yl)pyrazolo[1,5-a]pyrimi- dine, L3 = 7-(4-chlorophenyl)-5-(pyridin-2-yl)pyrazolo[1,5-a]pyrimidine, L4 = 7-(2-chlorophenyl) -5-(pyridin-2-yl)pyrazolo[1,5-a]pyrimidine, L5 = 7-(4-methoxyphenyl)-5-(pyridin-2-yl)pyrazolo [1,5-a]pyrimidine, L6 = 5-(pyridin-2-yl)-7-(p-tolyl)pyrazolo[1,5-a]pyrimidine were synthesized and characterized by 13C-APT, 1H-NMR, IR, electronic spectra, magnetic moment and conductance measurement. The anti-proliferative activity on HCT116 cells by MTT assay suggests potent cytotoxic nature of complexes, even some complexes have better activity than standard drug cisplatin, oxaliplatin, and carboplatin. The complexes found to have better antimicrobial activity compare to pyrazolo pyrimidine ligands. The theoretical study of compounds-DNA interactions was examined by molecular docking as a supportive tool to the experimental data, which suggests the groove mode of binding. The values of docking energy for compounds-DNA interaction were found in the range of -230.31 to -288.34 kJ/mol. The intrinsic binding constant values of complexes (1.1-3.5×105 M-1) were found higher than the ligands (0.32-1.8×105 M-1).

Synthesis, Characterization, Antimicrobial Activity, and Genotoxicity Assessment of Two Heterocyclic Compounds Containing 1,2,3-Selena- or 1,2,3-Thiadiazole Rings.

New 1,2,3-thiadiazole and 1,2,3-selenadiazole derivatives, (4-[4-((4-bromobenzyl)oxy)-phenyl]-1,2,3-thiadiazole (5a), 4-[4-((4-chlorobenzyl)oxy)-phenyl]-1,2,3-thiadiazole (5b)), (4-[4-((4-bromobenzyl)oxy)-phenyl]-1,2,3-selenadiazole (6a), and 4-[4-((4-chlorobenzyl)oxy)-phenyl]-1,2,3-selenadiazole (6b)), were prepared and screened in vitro for their antimicrobial activity against various pathogenic microbes. In addition, two compounds (5a and 6a) were examined for their in vivo genotoxicity using rats and an 8-hydroxy-2'-deoxyguanosine (8-OHdG) assay. Compounds 5a and 5b were found to be highly active against Gram-positive and Gram-negative bacteria. In addition, a significant inhibition of urinary 8-OHdG level (50.2%) was observed upon treatment of animals with 500 mg/kg body weight (b.w.) of compound 6a (p < 0.0001). However, compound 5a increased urinary 8-OHdG levels. The lethal dose (LD50) values for compounds 5a and 6a were determined by an up-and-down procedure (OECD 425; OECD 1998), which showed that these compounds are safe, since the LD50 was >5000 mg/kg b.w. Thus, the tested compounds might have the potential for use as antibiotics, since they have low genotoxicity and strong antimicrobial activity.

Detoxification of Heterocyclic Aromatic Amines by Probiotic to Inhibit Medical Hazards.

Cancer is the second leading factor of human death in the world. Long-term consumption of cooked red meat brings about various types of cancers like colorectal cancer due to the formation of Heterocyclic Aromatic Amines (HAAs) during the heating process of meat. There are various solutions for the reduction of these toxicants. The aim of this article is to describe probiotic as one of the possible strategies for bioremoval of these carcinogenic and mutagenic substances and change food to functional one as well. The mechanism of biodetoxification is binding by probiotics, which depends on some variables including the probiotic characteristics, kind and content of the mutagens, as well as some properties of media. In this article, after introducing detoxification ability of probiotics and listing of all reported probiotics in this field, the influencing variables are surveyed and finally, opportunities and problems of HAA bioremoval by probiotics are described.

Synthesis and characterization of silver nanoparticles using Caesalpinia pulcherrima flower extract and assessment of their in vitro antimicrobial, antioxidant, cytotoxic, and genotoxic activities.

Caesalpinia pulcherrima flower extract mediated synthesis of silver nanoparticles was attempted in the present work including optimization of some procedure parameters. Characterization of synthesized silver nanoparticles was done by various spectral analyses. The size of synthesized silver nanoparticles was 12 nm and they were spherical in shape. The green synthesized silver nanoparticles were further evaluated for antimicrobial, antioxidant, cytotoxic, and genotoxic activities; they showed good antimicrobial, antioxidant, and cytotoxic effects. Genotoxic study revealed non-toxic nature at lower concentration. Overall results suggest that the synthesized silver nanoparticles have pronounced applicability in pharmaceutical and biomedical field.

Synthesis, characterization, and determination of genotoxic effect of a novel dimeric 8-hydroxyquinoline Cd(II) SCN complex.

In this study, a Cd(II) complex was synthesized using 8-hydroxyquinoline and thiocyanate as the ligands and structurally characterized with the combination of FTIR, 1H-NMR, 13C-NMR, UV-vis, and MS spectral data. Then, genotoxic effects of the prepared complex were investigated. Genotoxic properties of the dimeric 8-hydroxyquinolinthiocyanatoCd(II) [Cd2(8Q)2(SCN)2] complex synthesized as drug raw material were analyzed in human peripheral blood lymphocytes. Concentrations of 1, 2, 4, 6, and 8 µg/mL [Cd2(8Q)2(SCN)2] were used for 24 and 48 h durations. [Cd2(8Q)2(SCN)2] significantly increased chromosomal aberrations (CAs) at 4, 6, and 8 µg/mL concentrations after a 24- h period and 2 and 4 µg/mL after a 48-h period. [Cd2(8Q)2(SCN)2] significantly decreased the mitotic index (MI) at all concentrations, both at 24 and 48 h. Micronuclei frequency (MN) was not affected by [Cd2(8Q)2(SCN)2] treatment compared with the control. After application for a 48 h period, 6 and 8 µg/mL concentrations showed toxic effects both in chromosomal abnormality and in micronucleus tests. It also decreased the cytokinesis-block proliferation index (CBPI), but this result was statistically significant only at 6 and 8 µg/mL concentrations. In the comet assay (single-cell gel electrophoresis (SCGE)), significant increases in comet tail length, tail moment, and tail intensity were observed at all concentrations. [Cd2(8Q)2(SCN)2] displays clastogenic effect in the concentrations used in human peripheral lymphocytes at chromosomal abnormality, micronucleus tests, and cytokinesis-block proliferation index parameters. Further studies should be conducted in other test systems to evaluate the complete genotoxic potential of [Cd2(8Q)2(SCN)2].

A Mechanistic Model for Colibactin-Induced Genotoxicity.

Precolibactins and colibactins represent a family of natural products that are encoded by the clb gene cluster and are produced by certain commensal, extraintestinal, and probiotic E. coli. clb+ E. coli induce megalocytosis and DNA double-strand breaks in eukaryotic cells, but paradoxically, this gene cluster is found in the probiotic Nissle 1917. Evidence suggests precolibactins are converted to genotoxic colibactins by colibactin peptidase (ClbP)-mediated cleavage of an N-acyl-d-Asn side chain, and all isolation efforts have employed ΔclbP strains to facilitate accumulation of precolibactins. It was hypothesized that colibactins form unsaturated imines that alkylate DNA by cyclopropane ring opening (2 → 3). However, as no colibactins have been isolated, this hypothesis has not been tested experimentally. Additionally, precolibactins A-C (7-9) contain a pyridone that cannot generate the unsaturated imines that form the basis of this hypothesis. To resolve this, we prepared 13 synthetic colibactin derivatives and evaluated their DNA binding and alkylation activity. We show that unsaturated imines, but not the corresponding pyridone derivatives, potently alkylate DNA. The imine, unsaturated lactam, and cyclopropane are essential for efficient DNA alkylation. A cationic residue enhances activity. These studies suggest that precolibactins containing a pyridone are not responsible for the genotoxicity of the clb cluster. Instead, we propose that these are off-pathway fermentation products produced by a facile double cyclodehydration route that manifests in the absence of viable ClbP. The results presented herein provide a foundation to begin to connect metabolite structure with the disparate phenotypes associated with clb+ E. coli.

Toxic effect and genotoxicity of the semisynthetic derivatives dillapiole ethyl ether and dillapiole n-butyl ether for control of Aedes albopictus (Diptera: Culicidae).

Two derivatives of dillapiole, dillapiole ethyl ether (1KL39-B) and butyl ether-n dillapiole (1KL43-C), were studied for their toxicity and genotoxicity against Aedes albopictus, to help develop new strategies for the control of this potential vector of dengue and other arboviruses, because it is resistant to synthetic insecticides. Eggs and larvae exposed to different concentrations of 1KL39-B (25, 30, 50, 70, and 80µg/mL) and of 1KL43-C (12.5, 20, 25, 30 and 40µg/mL) exhibited toxicity and susceptibility, with 100% mortality. The LC50 was 55.86±1.57µg/mL for 1KL39-B and 25.60±1.24µg/mL for 1KL43-C, while the LC90 was 70.12µg/mL for 1KL39-B and 41.51µg/mL for 1KL43-C. The gradual decrease in oviposition of the females of the G1 to G4 generations was proportional to the increase in concentrations of these compounds, which could be related to the cumulative effect of cell anomalies in neuroblasts and oocytes (P<0.05), including micronuclei, budding, multinucleated cells and nuclear bridges. These findings showed that both 1KL39-B and 1KL43-C can serve as potential alternatives in the control of A. albopictus.

Genotoxicity and cytotoxicity assessment of new ethyl-carbamates with ixodicidal activity.

The mammalian erythrocyte micronucleus test was used on the peripheral blood of Wistar rats exposed to two new ethyl-carbamates: ethyl-4-bromophenyl-carbamate (LQM 919) and ethyl-4-chlorophenyl-carbamate (LQM 996) to analyze their genotoxic potential. The mitotic index and cell proliferation kinetics in human lymphocyte cultures in the presence of these ethyl-carbamates were used to evaluate cytotoxicity and cytostaticity respectively. Exposure to greater acute doses (300mg/kg) and to all of the subchronic doses (12.5, 25 and 50mg/kg daily for 90 days) of these ethyl-carbamates induced an increased frequency (p<0.05) of micro-nucleated polychromatic erythrocytes (MN-PCE) compared with rats not exposed to the ethyl-carbamates. Increases in MN-PCE was higher in males than in females exposed to LQM 996 50mg/Kg (p<0.05). All observed changes in rats return 21days after suspending ethyl-carbamate exposure. The highest concentration (0.3mM) of both ethyl-carbamates in lymphocyte cultures increased the percentage of cells in first division metaphase and decreased the percentage of cells in third division metaphase, indicating an increase in cell cycle length or a possible cell cycle arrest in metaphase (cytostatic effect). The results of this study show that the evaluated ethyl-carbamates may induce genotoxic damage in rats and alterations in the human lymphocyte cell cycle.

Evaluation of DNA Binding, Radicals Scavenging and Antimicrobial Studies of Newly Synthesized N-Substituted Naphthalimides: Spectroscopic and Molecular Docking Investigations.

In this study, we investigated a new series of naphthalimide based Schiff base compounds as potential DNA binding, antioxidant and antimicrobial agents. The structural characterization of synthesized compounds was carried out with the aid of elemental analysis and spectroscopic techniques (UV-vis., IR, (1)H and (13)C NMR). The DNA binding properties of target compounds against Ct-DNA (calf thymus) have been investigated in detail by numerous biophysical techniques (UV-vis, fluorescence, ethidium bromide displacement assay, Time resolved fluorescence, viscosity, cyclic voltammetry and circular dichorism) and the evidences have suggested that the test compounds could interact with DNA via intercalative binding. The extent of DNA binding (Kb) of these compounds follow the order of 3b (3.33 × 10(4) M(-1)) > 3a (2.25 × 10(4) M(-1)) > 3c (2 × 10(4) M(-1)), suggesting that compound 3b binds more strongly to Ct- DNA than the compounds 3a and 3c. Molecular docking results further support intercalative binding of test compounds with DNA. The binding energies of docked compounds (3a-3c) were found to be -8.20 to -8.69 kcal/ mol, suggesting greater binding affinity to Ct-DNA. The synthesized compounds displayed potential antimicrobial activities against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Salmonella typhimurium. Compound 3c has emerged as most active against all the four tested bacterial strains with MIC value in the range of 0.031-0.062 mg/mL. In the mutagenicity studies, all the test compounds were found to be non-mutagenic both in the presence and absence of metabolic activation. Furthermore, the antioxidant activity experiments show that these compounds exhibited potential scavenging activities against DPPH and H2O2 radicals.

A new synthetic resorcinolic lipid 3-heptyl-3,4,6-trimethoxy-3H-isobenzofuran-1-one: evaluation of toxicology and ability to potentiate the mutagenic and apoptotic effects of cyclophosphamide.

Resorcinolic lipids have important biological actions, including anti-carcinogenic activity. Therefore, we evaluated the mutagenic, genotoxic, immunomodulatory and apoptotic potential and the biochemical and histopathological changes caused by the synthetic resorcinolic lipid 3-Heptyl-3,4,6-trimethoxy-3H-isobenzofuran-1-one, (AMS35AA; 10, 20 and 40 mg/kg) alone or in combination with cyclophosphamide (100 mg/kg) in Swiss mice. The results indicated that AMS35AA is not genotoxic or mutagenic and does not alter liver or kidney histology. However, the compound does cause an increase (p < 0.05) in the levels of glutamic-oxaloacetic transaminase and creatinine and in splenic phagocytosis and liver and kidney apoptosis. When combined with cyclophosphamide, AMS35AA caused increased (p < 0.05) mutagenic damage (although the compound had anti-genotoxic activity), splenic phagocytosis, neutropenia and glutamic-oxaloacetic transaminase and creatinine levels (even in the absence of histological damage) and induced liver and kidney apoptosis. We conclude that this resorcinolic lipid may be an important chemotherapy adjuvant that can potentiate mutagenic damage and increase apoptosis caused by cyclophosphamide without causing adverse effects. In addition, the immunomodulatory activity of the compound should be noted, which counters reductions in lymphocyte number, a primary side effect of cyclophosphamide in cancer therapy.

Improved synthesis and mutagenicity of oligonucleotides containing 5-hydroxymethylcytosine, 5-formylcytosine and 5-carboxylcytosine.

5-Formylcytosine (fC or (5-CHO)dC) and 5-carboxylcytosine (caC or (5-COOH)dC) have recently been identified as constituents of mammalian DNA. The nucleosides are formed from 5-methylcytosine (mC or (5-Me)dC) via 5-hydroxymethylcytosine (hmC or (5-HOMe)dC) and are possible intermediates of an active DNA demethylation process. Here we show efficient syntheses of phosphoramidites which enable the synthesis of DNA strands containing these cytosine modifications based on Pd(0)-catalyzed functionalization of 5-iododeoxycytidine. The first crystal structure of fC reveals the existence of an intramolecular H-bond between the exocyclic amine and the formyl group, which controls the conformation of the formyl substituent. Using a newly designed in vitro mutagenicity assay we show that fC and caC are only marginally mutagenic, which is a prerequisite for the bases to function as epigenetic control units.

[The chiral mutagens: cytogenetic effects on higher plants].

The paper covers investigation of cytogenetic activity of chiral mutagens and their specific effects on the plant cells chromosomes of soft winter wheat (Triticum aestivum L.). Comparative analysis of cytogenetic activity of chiral NEU: S(+)1-N-nitroso- 1-N-methyl-3-N-sec-buthylureas (S(+)NMsBU) and R(-)1-N-nitroso- 1N-methyl-3-Nsec-buthylureas (R(-)NMsBU) on winter wheat was performed. As it was shown by the frequency of chromosomal aberrations the S(+) stereoisomer was twice more active than R(-). In addition to typical anaphase aberrations (fragments, bridges, lagging chromosomes) the numerous mitosis pathologies were revealed - K-mitoses, hyperspiralization and despiralization of chromosomes, unequal allocation of chromosomes between the daughter nuclei, mass fragmentation, nondisjunction and chromosome adhesion, three-pole mitoses, etc. Neither of the mentioned pathologies was observed under the action of NEU and gamma-rays.

Novel trans-platinum complexes of the histone deacetylase inhibitor valproic acid; synthesis, in vitro cytotoxicity and mutagenicity.

The first examples of Pt complexes of the well known anti-epilepsy drug and histone deacetylase inhibitor, valproic acid (VPA), are reported. Reaction of the Pt(II) am(m)ine precursors trans-[PtCl(2)(NH(3))(py)] and trans-[PtCl(2)(py)(2)] with silver nitrate and subsequently sodium valproate gave trans-[Pt(VPA(-1H))(2)(NH(3))(py)] and trans-[Pt(VPA(-1H))(2)(py)(2)], respectively. The valproato ligands in both complexes are bound to the Pt(II) centres via the carboxylato functionality and in a monodentate manner. The X-ray crystal structure of trans-[Pt(VPA(-1H))(2)(NH(3))(py)] is described. Replacement of the dichlorido ligands in trans-[PtCl(2)(py)(2)] and trans-[PtCl(2)(NH(3))(py)] by valproato ligands (VPA(-1H)) to yield trans-[Pt(VPA(-1H))(2)(py)(2)] and trans-[Pt(VPA(-1H))(2)(NH(3))(py)] respectively, significantly enhanced cytotoxicity against A2780 (parental) and A2780 cisR (cisplatin resistant) ovarian cancer cells. The mutagenicity of trans-[Pt(VPA(-1H))(2)(NH(3))(py)] and trans-[Pt(VPA(-1H))(2)(py)(2)] was determined using the Ames test and is also reported.

Trimethylsilyldiazomethane: a safe non-explosive, cost effective and less-toxic reagent for phenol derivatization in GC applications.

Diazomethane is a highly explosive and toxic gas routinely employed for the quantitative and clean derivatization of phenols. We investigated the commercially available trimethylsilyldiazomethane in the presence of diisopropylethylamine as a safe, non-explosive and less-toxic alternative using six phenolic polychlorinated biphenyls as model analytes and fluoro-tagged analogues as internal standards. We compared yields and derivatization times of each method employing a liver microsomal extract as a real matrix. Steric hindrance and electronic properties of the analytes were also investigated. The alternative method afforded equal to higher derivatization yields with increased reaction times, up to 100 min, while explosion and toxic exposure risks were minimized and cost efficiency was increased above 25%. These findings demonstrate that non-explosive trimethylsilyl diazomethane produces comparable derivatization results to the dangerous diazomethane under the conditions studied.

Mutagenic potential of DNA glycation: miscoding by (R)- and (S)-N2-(1-carboxyethyl)-2'-deoxyguanosine.

Elevated circulating glucose resulting from complications of obesity and metabolic disease can result in the accumulation of advanced glycation end products (AGEs) of proteins, lipids, and DNA. The formation of DNA-AGEs assumes particular importance as these adducts may contribute to genetic instability and elevated cancer risk associated with metabolic disease. The principal DNA-AGE, N(2)-(1-carboxyethyl)-2'-deoxyguanosine (CEdG), is formed as a mixture of R and S isomers at both the polymer and monomer levels. In order to examine the miscoding potential of this adduct, oligonucleotides substituted with (R)- and (S)-CEdG and the corresponding triphosphates (R)- and (S)-CEdGTP were synthesized, and base-pairing preferences for each stereoisomer were examined using steady-state kinetic approaches. Purine dNTPs were preferentially incorporated opposite template CEdG when either the Klenow (Kf(-)) or Thermus aquaticus (Taq) polymerases were used. The Kf(-) polymerase preferentially incorporated dGTP, whereas Taq demonstrated a bias for dATP. Kf(-) incorporated purines opposite the R isomer with greater efficiency, but Taq favored the S isomer. Incorporation of (R)- and (S)-CEdGTP only occurred opposite dC and was catalyzed by Kf(-) with equal efficiencies. Primer extension from a 3'-terminal CEdG was observed only for the R isomer. These data suggest CEdG is the likely adduct responsible for the observed pattern of G transversions induced by exposure to elevated glucose or its alpha-oxoaldehyde decomposition product methylglyoxal. The results imply that CEdG within template DNA and the corresponding triphosphate possess different syn/anti conformations during replication which influence base-pairing preferences. The implications for CEdG-induced mutagenesis in vivo are discussed.

Improved syntheses of non-dioxin-like polychlorinated biphenyls (PCBs) and some of their sulfur-containing metabolites.

Polychlorinated biphenyls (PCBs) are an important group of environmental pollutants that have been associated with adverse human health effects. Despite recent advances in their synthesis, the availability of PCB congeners in sufficient quantity and purity still represents one obstacle in the investigation of their biological effects. We report herein improved syntheses of PCB congeners (and their metabolites) containing two or more ortho-chlorine substituents. The Suzuki coupling reaction at 110 °C yielded PCB congeners with a 2,2'-substitution pattern in good yields (78-99%), but failed to give PCB congeners with 3 or 4 ortho chlorine substituents. Symmetrically substituted PCB congeners with multiple ortho chlorine substituents were obtained in 20-52% yields using a modified Ullmann coupling reaction. The yield of the coupling increased with increasing degree of chlorination of the starting material. The modified Ullmann coupling reaction employed much milder reaction conditions (copper-bronze/CuCl in N-methylpyrrolidinone, 110 °C) and, therefore, appears to be advantageous compared to the classical Ullmann coupling reaction (copper-bronze, no solvent, 230 °C). PCBs 136 and 155 prepared via the modified Ullmann coupling reaction were nitrated and reduced with Na(2)S(2)O(4) to the corresponding amino-PCBs. Subsequently, the amino-PCBs were converted into sulfur-containing PCB metabolites or PCB 184 via the corresponding diazonium salt. These modified reaction conditions allow the synthesis of large quantities of pure, non-dioxin-like PCB congeners and their sulfur-containing metabolites for environmental and toxicological studies by overcoming problems associated with classical PCB synthesis strategies.