Heike Bruhn

Institute of Molecular Biology, Mayence, Rheinland-Pfalz, Germany

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Publications (10)31.64 Total impact

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    ABSTRACT: Five manganese(I) tricarbonyl complexes of the general formula [Mn(CO)3(bpyR,R)(azole)]PF6 with R = H, COOCH3, and azole = ketoconazole (ktz), miconazole (mcz), and clotrimazole (ctz) were synthesized and fully charaterized, including X-ray structure analysis for the ctz compound. The antibacterial activity on a panel of eight Gram-positive and Gram-negative bacterial strains was determined. While there was no effect on the latter microorganisms, the ctz complex showed submicromolar activity on Staphylococcus aureus and S. epidermidis with MIC values of 0.625 μM. Antiparasitic activity was investigated on Leishmania major and Trypanosoma brucei. Coordination of the organic azole drugs to the Mn(CO)3 moiety led to complexes with low micromolar IC50 values, but their potential for antileishmanial therapy is low due to comparable toxicity on mammalian cell lines 293T and J774.1. In contrast, the antitrypanosomal activity is much more promising, and the most potent compound incorparting the ktz ligand has an IC50 value on T. brucei of 0.7 μM with selectivity on parasitic over mammalian cells as expressed by a selectivity index above 10. These results demonstrate that metal coordination of established drugs can significantly improve their biological activity and expand their range of medicinal applications. (Chemical Equation Presented).
    No preview · Article · Jul 2015 · Organometallics
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    ABSTRACT: A poorly water soluble acidic active pharmaceutical ingredient (API) was transformed into an ionic liquid (IL) aiming at faster and higher oral availability in comparison to a prodrug. API preparations were characterized in solid state by single crystal and powder diffraction, NMR, DSC, IR and in solution by NMR and ESI-MS. Dissolution and precipitation kinetics were detailed as was the role of the counterion on API supersaturation. Transepithelial API transport through Caco-2 monolayers and counterion cytotoxicity were assessed. The mechanism leading to a 700 fold faster dissolution rate and longer duration of API supersaturation of the ionic liquid in comparison to the free acid was deciphered. Transepithelial transport was about three times higher for the IL in comparison to the prodrug when substances were applied as suspensions with the higher solubility of the IL outpacing the higher permeability of the prodrug. The counterion was nontoxic with IC50 values in the upper μM / lower mM range in cell lines of hepatic and renal origin as well as in macrophages. The IL approach was instrumental for tuning physico-chemical API properties, while avoiding the inherent need for structural changes as required for prodrugs.
    No preview · Article · Dec 2014 · Pharmaceutical Research
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    ABSTRACT: Isoquinolines (IQs) are natural substances with an antibiotic potential we aim to optimize. Specifically, IQ-238 is a synthetic analog of the novel-type N,C-coupled naphthylisoquinoline (NIQ) alkaloid ancisheynine. Recently, we developed and tested other IQs such as IQ-143. By utilizing genome-wide gene expression data, metabolic network modelling and voronoi tessalation based data analysis–as well as cytotoxicity measurements, chemical properties calculations and principal component analysis of the NIQs–we show that IQ-238 has strong antibiotic potential for staphylococci and low cytotoxicity against murine or human cells. Compared to IQ-143, systemic effects are less pronounced. Most enzyme activity changes due to IQ-238 are located in the carbohydrate metabolism. Validation includes metabolite measurements on biological replicates. IQ-238 delineates key properties and a chemical space for a good therapeutic window. The combination of analysis methods allows suggestions for further lead development and yields an in-depth look at staphylococcal adaptation and network changes after antibiosis. Results are compared to eukaryotic host cells.
    No preview · Article · Nov 2014 · International Journal of Medical Microbiology
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    ABSTRACT: Potent compounds do not necessarily make the best drugs in the market. Consequently, with the aim to describe tools that may be fundamental for refining the screening of candidates for animal and preclinical studies and further development, molecules of different structural classes synthesized within the frame of a broad screening platform were evaluated for their trypanocidal activities, cytotoxicities against murine macrophages J774.1 and selectivity indices, as well as for their ligand efficiencies and structural chemical properties. To advance into their modes of action, we also describe the morphological and ultrastructural changes exerted by selected members of each compound class on the parasite Trypanosoma brucei. Our data suggest that the potential organelles targeted are either the flagellar pocket (compound 77, N-Arylpyridinium salt; 15, amino acid derivative with piperazine moieties), the endoplasmic reticulum membrane systems (37, bisquaternary bisnaphthalimide; 77, N-Arylpyridinium salt; 68, piperidine derivative), or mitochondria and kinetoplasts (88, N-Arylpyridinium salt; 68, piperidine derivative). Amino acid derivatives with fumaric acid and piperazine moieties (4, 15) weakly inhibiting cysteine proteases seem to preferentially target acidic compartments. Our results suggest that ligand efficiency indices may be helpful to learn about the relationship between potency and chemical characteristics of the compounds. Interestingly, the correlations found between the physico-chemical parameters of the selected compounds and those of commercial molecules that target specific organelles indicate that our rationale might be helpful to drive compound design toward high activities and acceptable pharmacokinetic properties for all compound families.
    No preview · Article · Nov 2014 · Parasitology Research
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    ABSTRACT: Four new N-heterocyclic carbene (NHC) rhodium and iridium complexes decorated with anionic or cationic pendant groups to increase their water solubility and biological activity have been synthesised and characterised. The lipophilicity of the complexes was determined and the complexes that contained cationic phosphonium groups can be considered delocalised lipophilic cations (DLCs). All complexes were tested for their antibacterial, antiparasitic and anticancer activity, with only the phosphonium-functionalised complexes showing moderate to high activity, whereas the exchange of metal from rhodium to iridium had a negligible effect. Most promising was the activity on Trypanosoma brucei, with IC50 values in the range of 150-400 nM and a selectivity index (SI) of up to 50. General toxicity on mammalian cell lines was a general problem, though, and needs to be mitigated in future work. Cellular uptake studies clearly confirmed that the cationic phosphonium groups facilitated uptake, which was linked with higher biological activity.
    No preview · Article · Nov 2013 · Berichte der deutschen chemischen Gesellschaft
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    ABSTRACT: Organometallic analogues of chloroquine show promise as new antimalarial agents capable of overcoming resistance to the parent drug chloroquine. Here, the synthesis and characterization of three new cymantrene (CpMn(CO)(3)) and cyrhetrene (CpRe(CO)(3)) 4-aminoquinoline conjugates with either an amine or amide linker are reported. The antimalarial activity of the new organometallic conjugates N-(2-(7-chloroquinolin-4-ylamino)ethyl)-4-cymantrenylbutanamide (3), N-(2-(7-chloroquinolin-4-ylamino)ethyl)-4-cyrhetrenylbutanamide (4) and N-(7-chloroquinolin-4-yl)-N'-(cymantrenylmethyl)ethane-1,2-diamine (6) was evaluated against a chloroquine-sensitive (CQS) and a chloroquine-resistant strain (CQR) of the malaria parasite Plasmodium falciparum. The cymantrene complex with an amine linker (6) showed good activity against the CQS strain but was inactive against the CQR strain. In contrast, cymantrene and cyrhetrene compounds with an amide linker were active against both the CQS and the CQR strain. In addition, the antibacterial, anti-trypanosomal and anti-leishmanial activity of the compounds was evaluated. Compound 6 showed submicromolar activity against Trypanosoma brucei at a concentration where the toxicity to normal human cells is low. No significant effect was noticed on the exchange of manganese for rhenium in the CpM(CO)(3) moiety in any of the biological assays.
    No preview · Article · Mar 2012 · Dalton Transactions
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    ABSTRACT: Screening of various bisquaternary bisnaphthalimides against a variety of human pathogens revealed one compound, designated MT02, with strong inhibitory effects against Gram-positive bacteria. The MICs ranged from 0.31 μg/ml against community-acquired methicillin-resistant Staphylococcus aureus (MRSA) lineage USA300 to 20 μg/ml against Streptococcus pneumoniae. Radioactive whole-cell labeling experiments indicated a strong impact of MT02 on bacterial DNA replication. DNA microarray studies generated a transcriptional signature characterized by stronger expression of genes involved in DNA metabolism, DNA replication, SOS response, and transport of positively charged compounds. Furthermore, surface plasmon resonance and gel retardation experiments demonstrated direct binding of MT02 to DNA in a concentration-dependent, reversible, and non-sequence-specific manner. The data presented suggest that the bisquaternary bisnaphthalimide MT02 exerts anti-Gram-positive activity by binding to DNA and thereby preventing appropriate DNA replication.
    Full-text · Article · Oct 2010 · Antimicrobial Agents and Chemotherapy
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    ABSTRACT: Fifteen new DOPA-derived pyrrole alkaloids, named baculiferins A-O (2-16), were isolated from the Chinese marine sponge Iotrochota baculifera, together with the known alkaloids purpurone (1) and ningalin A (17). Most of the new compounds contain one to three O-sulfate units. Their structures were determined by extensive spectroscopic analysis including (1)H and (13)C NMR (COSY, HMQC, HMBC) and ESIMS data. A possible pathway for the biosynthetic origin of the isolated alkaloids is proposed, in which DOPA is assumed to be a joint biogenetic precursor. Baculiferins C, E-H, and K-N (4, 6-9, 12-15) were found to be potent inhibitors against the HIV-1 IIIB virus in both, MT4 and MAGI cells. Additional bioassay revealed that baculiferins could dramatically bind to the HIV-1 target proteins Vif, APOBEC3G, and gp41, for which structure-activity relationships are discussed.
    Full-text · Article · Aug 2010 · Bioorganic & medicinal chemistry
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    ABSTRACT: Warnericin RK is the first antimicrobial peptide known to be active against Legionella pneumophila, a pathogen bacterium that is responsible for severe pneumonia. Strikingly, this peptide displays a very narrow range of antimicrobial activity, almost limited to the Legionella genus, and a hemolytic activity. A similar activity has been described for delta-lysin, a well-known hemolytic peptide of Staphylococci that has not been described as antimicrobial. In this study we aimed to understand the mode of action of warnericin RK and to explain its particular target specificity. We found that warnericin RK permeabilizes artificial membranes in a voltage-independent manner. Osmotic protection experiments on erythrocytes showed that warnericin RK does not form well-defined pores, suggesting a detergent-like mode of action, as previously described for delta-lysin at high concentrations. Warnericin RK also permeabilized Legionella cells, and these cells displayed a high sensitivity to detergents. Depending on the detergent used, Legionella was from 10- to 1000-fold more sensitive than the other bacteria tested. Finally, the structure of warnericin RK was investigated by means of circular dichroism and NMR spectroscopy. The peptide adopted an amphiphilic alpha-helical structure, consistent with the proposed mode of action. We conclude that the specificity of warnericin RK toward Legionella results from both the detergent-like mode of action of the peptide and the high sensitivity of these bacteria to detergents.
    Full-text · Article · Oct 2009 · Biophysical Journal
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    ABSTRACT: Pathogenomics – Study of Pathogenesis in Genomic and Post-Genomic EraImmunotherapy and Vaccine Development – Alternative Strategies to Antibiotics for the Treatment of Infections by Multiresistant Bacterial PathogensAntibiotics – Current Status and Future ChallengesConclusion AcknowledgmentsReferences
    No preview · Article · Jul 2009