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.

Antibacterial and Antibiofilm Potentials of Marine Pyrrole-2-Aminoimidazole Alkaloids and their Synthetic Analogs.

Pyrrole-2-aminoimidazole compounds are found in marine organisms, mainly as secondary metabolites in various marine sponges. Studies of natural pyrrole-2-aminoimidazole compounds showed that they possess different pharmacological properties, such as antimicrobial, antibiofilm, immunosuppressive and anticancer activities. Many analogs of the natural compounds have been synthesized to improve their biological activities. This review focuses on the antibacterial and antibiofilm potentials of natural pyrrole-2-aminoimidazoles and their synthetic analogs and derivatives, as well as on the structure-activity relationships of the most promising compounds. Known molecular targets of these compounds in bacterial cells are also described here, as is the synergistic activity of the pyrrole- 2-aminoimidazoles and conventional antibiotics.

Benzothiazole-based Compounds in Antibacterial Drug Discovery.

Numerous compounds with a benzothiazole scaffold that have been described in the literature show promising activities against several Gram-positive and Gramnegative bacteria, and also against Mycobacterium tuberculosis. Benzothiazole-based antibacterial compounds bind to different biological targets in bacterial cells and have been shown to be inhibitors of enzymes that are important for essential processes in the bacterial cells, such as cell-wall synthesis, cell division, and DNA replication, or are important for different biosynthetic pathways of essential compounds in bacterial cells, such as the biosynthesis of histidine and biotin. This review focuses on the antibacterial potential of benzothiazole-based compounds, in terms of their specific interactions with targets in bacterial cells. We assess the importance of the benzothiazole scaffold in the discovery of new antibacterial compounds, the potential of benzothiazole-based compounds against resistant bacterial strains, optimization of their antibacterial activity, and the future perspectives of benzothiazole-based antibacterials.

Discovery of Benzothiazole Scaffold-Based DNA Gyrase B Inhibitors.

Bacterial DNA gyrase and topoisomerase IV control the topological state of DNA during replication and are validated targets for antibacterial drug discovery. Starting from our recently reported 4,5,6,7-tetrahydrobenzo[1,2-d]thiazole-based DNA gyrase B inhibitors, we replaced their central core with benzothiazole-2,6-diamine scaffold and interchanged substituents in positions 2 and 6. This resulted in equipotent nanomolar inhibitors of DNA gyrase from Escherichia coli displaying improved inhibition of Staphylococcus aureus DNA gyrase and topoisomerase IV from both bacteria. Compound 27 was the most balanced inhibitor of DNA gyrase and topoisomerase IV from both E. coli and S. aureus. The crystal structure of the 2-((2-(4,5-dibromo-1H-pyrrole-2-carboxamido)benzothiazol-6-yl)amino)-2-oxoacetic acid (24) in complex with E. coli DNA gyrase B revealed the binding mode of the inhibitor in the ATP-binding pocket. Only some compounds possessed weak antibacterial activity against Gram-positive bacteria. These results provide a basis for structure-based optimization toward dual DNA gyrase and topoisomerase IV inhibitors with antibacterial activity.