Improved small-molecule macroarray platform for the rapid synthesis and discovery of antibacterial chalcones

Promising antibacterial agents against multidrug resistant Staphylococcus aureus

Rapid emergence of multidrug resistant Staphylococcus aureus infections has created a critical health menace universally. Resistance to all the available chemotherapeutics has been on rise which led to WHO to stratify Staphylococcus aureus as high tier priorty II pathogen. Hence, discovery and development of new antibacterial agents with new mode of action is crucial to address the multidrug resistant Staphylococcus aureus infections. The egressing understanding of new antibacterials on their biological target provides opportunities for new therapeutic agents. This review underlines on various aspects of drug design, structure activity relationships (SARs) and mechanism of action of various new antibacterial agents and also covers the recent reports on new antibacterial agents with potent activity against multidrug resistant Staphylococcus aureus. This review provides attention on in vitro and in vivo pharmacological activities of new antibacterial agents in the point of view of drug discovery and development.

Fine-Tuning Covalent Inhibition of Bacterial Quorum Sensing

Emerging antibiotic resistance among human pathogens has galvanized efforts to find alternative routes to combat bacterial virulence. One new approach entails interfering with the ability of bacteria to coordinate population-wide gene expression, or quorum sensing (QS), thus inhibiting the production of virulence factors and biofilm formation. We have recently developed such a strategy by targeting LasR, the master regulator of QS in the opportunistic human pathogen Pseudomonas aeruginosa, through the rational design of covalent inhibitors closely based on the core structure of the native ligand. We now report several groups of new inhibitors, one of which, fluoro-substituted ITC-12, displayed complete covalent modification of LasR, as well as effective QS inhibition in vitro and promising in vivo results. In addition to their potential clinical relevance, this series of synthetic QS modulators can be used as a tool to further unravel the complicated QS regulation in P. aeruginosa.

Synthesis and spectroscopic studies of berberine immobilized modified cellulose material

This report describes the synthesis, characterization and spectroscopic studies of berberine immobilized modified cellulose materials, which could be a promising new biocompatible fluorescence material because berberine is a natural fluorescent molecule having important pharmacological aspects including selective binding with DNA G-quadruplex.

Chemical methods to interrogate bacterial quorum sensing pathways

Bacteria frequently manifest distinct phenotypes as a function of cell density in a phenomenon known as quorum sensing (QS). This intercellular signalling process is mediated by "chemical languages" comprised of low-molecular weight signals, known as autoinducers, and their cognate receptor proteins. As many of the phenotypes regulated by QS can have a significant impact on the success of pathogenic or mutualistic prokaryotic-eukaryotic interactions, there is considerable interest in methods to probe and modulate QS pathways with temporal and spatial control. Such methods would be valuable for both basic research in bacterial ecology and in practical medicinal, agricultural, and industrial applications. Toward this goal, considerable recent research has been focused on the development of chemical approaches to study bacterial QS pathways. In this Perspective, we provide an overview of the use of chemical probes and techniques in QS research. Specifically, we focus on: (1) combinatorial approaches for the discovery of small molecule QS modulators, (2) affinity chromatography for the isolation of QS receptors, (3) reactive and fluorescent probes for QS receptors, (4) antibodies as quorum "quenchers," (5) abiotic polymeric "sinks" and "pools" for QS signals, and (6) the electrochemical sensing of QS signals. The application of such chemical methods can offer unique advantages for both elucidating and manipulating QS pathways in culture and under native conditions.

Selecting, Acquiring, and Using Small Molecule Libraries for High-Throughput Screening

The selection, acquisition and use of high quality small molecule libraries for screening is an essential aspect of drug discovery and chemical biology programs. Screening libraries continue to evolve as researchers gain a greater appreciation of the suitability of small molecules for specific biological targets, processes and environments. The decisions surrounding the make-up of any given small molecule library is informed by a multitude of variables and opinions vary on best-practices. The fitness of any collection relies upon upfront filtering to avoiding problematic compounds, assess appropriate physicochemical properties, install the ideal level of structural uniqueness and determine the desired extent of molecular complexity. These criteria are under constant evaluation and revision as academic and industrial organizations seek out collections that yield ever improving results from their screening portfolios. Practical questions including cost, compound management, screening sophistication and assay objective also play a significant role in the choice of library composition. This overview attempts to offer advice to all organizations engaged in small molecule screening based upon current best practices and theoretical considerations in library selection and acquisition.

Expedient construction of small molecule macroarrays via sequential palladium- and copper-mediated reactions and their ex situ biological testing

We report the highly efficient syntheses of a series of focused libraries in the small molecule macroarray format using Suzuki-Miyaura and copper-catalyzed azide-alkyne cycloaddition (or "click") reactions. The libraries were based on stilbene and triazole scaffolds, which are known to have a broad range of biological activities, including quorum-sensing (QS) modulation in bacteria. The library products were generated in parallel on the macroarray in extremely short reaction times (~10-20 min) and isolated in excellent purities. Biological testing of one macroarray library post-cleavage (ex situ) revealed several potent agonists of the QS receptor, LuxR, in Vibrio fischeri. These synthetic agonists, in contrast to others that we have reported, were only active in the presence of the native QS signal in V. fischeri, which is suggestive of a different mode of activity. Notably, the results presented herein showcase the ready compatibility of the macroarray platform with chemical reactions that are commonly utilized in small molecule probe and drug discovery today. As such, this work serves to expand the utility of the small molecule macroarray as a rapid and operationally straightforward approach toward the synthesis and screening of bioactive agents.

Small-molecule proteostasis regulators for protein conformational diseases

Protein homeostasis (proteostasis) is essential for cellular and organismal health. Stress, aging, and the chronic expression of misfolded proteins, however, challenge the proteostasis machinery and the vitality of the cell. Enhanced expression of molecular chaperones, regulated by heat shock transcription factor-1 (HSF-1), has been shown to restore proteostasis in a variety of conformational disease models, suggesting a promising therapeutic approach. We describe the results of a ∼900,000 small molecule screen that identified novel classes of small molecule proteostasis regulators (PRs) that induce HSF-1-dependent chaperone expression and restore protein folding in multiple conformational disease models. The beneficial effects to proteome stability are mediated by HSF-1, DAF-16/FOXO, SKN-1/Nrf-2, and the chaperone machinery through mechanisms that are distinct from current known small molecule activators of the HSR. We suggest that modulation of the proteostasis network by PRs represents a promising therapeutic approach for the treatment of a variety of protein conformational diseases.