Discovery of substituted oxadiazoles as a novel scaffold for DNA gyrase inhibitors

DNA gyrase and topoisomerase IV are type IIa topoisomerases that are essential bacterial enzymes required to oversee the topological state of DNA during transcription and replication processes. Their ATPase domains, GyrB and ParE, respectively, are recognized as viable targets for small molecule inhibitors, however, no synthetic or natural product GyrB/ParE inhibitors have so far reached the clinic for use as novel antibacterial agents, except for novobiocin which was withdrawn from the market. In the present study, a series of substituted oxadiazoles have been designed and synthesized as potential DNA gyrase inhibitors. Structure-based optimization resulted in the identification of compound 35, displaying an IC50 of 1.2 mu M for Escherichia coli DNA gyrase, while also exhibiting a balanced low micromolar inhibition of E. coli topoisomerase IV and of the respective Staphylococcus aureus homologues. The most promising inhibitors identified from each series were ultimately evaluated against selected Grampositive and Gram-negative bacterial strains, of which compound 35 inhibited Enterococcus faecalis with a MIC90 of 75 mu M. Our study thus provides further insight into the structural requirements of substituted oxadiazoles for dual inhibition of DNA gyrase and topoisomerase IV. (C) 2017 Elsevier Masson SAS. All rights reserved.Peer reviewe

Screening and Characterisation of Antimicrobial Properties of Semisynthetic Betulin Derivatives

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Utilization of in situ ELISA method for examining Trk receptor phosphorylation in cultured cells

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Defining conditions for biofilm inhibition and eradication assays for Gram-positive clinical reference strains

BackgroundBiofilms are formed by a complex bacterial community encapsulated by a polymeric matrix, with strong adherent properties and persistent phenotype. Biofilms are considered one of the most challenging areas of modern medicine. Existing antibiotics have been developed against free-floating bacterial cells, and thus, many treatments of biofilm-related infection fail. In this study, we compared the effects of different media on biofilm growth of clinical reference strains of Staphylococci and Enterococci, including multi-drug resistant representatives. Further, we optimized the resazurin-based assay for determining the minimal biofilm inhibitory concentration (MBIC) of standard antibiotics, and evaluated its use for the determination of minimal biofilm eradication concentration (MBEC).ResultsWe showed that tryptic soy broth supplemented with 1% glucose was an optimal media for maximum biofilm growth of all strains tested, with an extended incubation time for Enterococci. A range of parameters were tested for the resazurin assay, including concentration, temperature and time of incubation. Using quality parameters to analyze the assay's performance, the conditions for the resazurin assay were set as follows: 4g/mL and 8g/mL, with incubation at 25 degrees C for 20min and 40min for Staphylococci and Enterococci, respectively.ConclusionsIn summary, we defined conditions for optimal biofilm growth and for standardized resazurin assay for MBIC determination against six Gram-positive clinical reference strains. We also observed that MBEC determination by the resazurin-based assay is limited due to the poor detection limit of the assay. Complementary cell counting data is needed for precise determination of MBEC.Peer reviewe

Natural Product - Drug Interactions and Their Evaluation Using a Caco-2 Cell Culture Model

Natural products, such as herbal medicinal products, food supplements, and functional food, are widely used to support well-being and for promoting health. In general, the effects of using these products are desired and beneficial, but unexpected adverse effects might also occur, especially when natural products are used with medication. Consumers do not often even know that they are exposed to bioactive compounds that might interact with the body and have effects on their well-being. One of the objectives of the World Health Organization is to promote herb-drug interaction monitoring, and it is important to know how marketed preparations and compounds from common foods interact when they are absorbed. In this review, we describe how a Caco-2 cell absorption model has been used to study how natural products, such as flaxseed, rapeseed, purple loosestrife, pine, echinacea, certain berries and herbs, anthranoid laxatives, and traditional medicinal plants, affect the absorption of co-administered drugs. We discuss the types of interactions and adverse effects that might occur and their possible reasons. Overall, we conclude that the Caco-2 cell absorption model is a useful tool for studying the absorption of natural products with drugs; and that to enable the safe use of natural products with medicines, concomitant use should be studied.Peer reviewe

Anti-influenza virus activity of benzo[d]thiazoles that target heat shock protein 90

Seasonal or pandemic influenza virus infections are a worldwide health problem requiring antiviral therapy. Since virus resistance to the established neuraminidase inhibitors and novel polymerase inhibitors is growing, new drug targets are needed. Heat shock protein 90 (Hsp90) is associated with several aspects of the influenza virus life cycle, and is considered a relevant host cell target. We report here on a series of benzo[d]thiazole and 4,5,6,7-tetrahydrobenzo[d]thiazole derivatives with robust and selective activities against influenza A (H1N1, H3N2) and influenza B viruses. Two compounds, 1 and 4, have low micromolar EC50 values and show high binding affinities for Hsp90, which suggests that inhibition of Hsp90 is the mechanism underlying their antiviral effects. These compounds represent suitable scaffolds for designing novel Hsp90 inhibitors with favourable activities against influenza virus.status: publishe