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[Display omitted] • New feature of Schiff base, inhibit enzyme that causing drug resistant, was found. • Compounds exhibited promising inhibition against metallo-β-lactamase. • Compounds restored antimicrobial activity of cefazolin against resistance bacteria. • From kinetics, thermodynamics and docking aspect, inhibit behavior was confirmed. • The most active compound was well tolerated with mouse fibroblast cells. The irregular use of antibiotics has created a natural selection pressure for bacteria to adapt resistance. Bacterial resistance caused by metallo-β-lactamases (MβLs) has been the most prevalent in terms of posing a threat to human health. The New Delhi metallo-β-lactamase-1 (NDM-1) has been shown to be capable of hydrolyzing almost all β-lactams. In this work, eight aromatic Schiff bases 1 – 8 were prepared and identified by enzyme kinetic assays to be the potent inhibitors of NDM-1 (except 4). These molecules exhibited a more than 95 % inhibition, and an IC 50 value in the range of 0.13–19 μM on the target enzyme, and 3 was found to be the most effective inhibitor (IC 50 = 130 nM). Analysis of structure–activity relationship revealed that the o -hydroxy phenyl improved the inhibitory activity of Schiff bases on NDM-1. The inhibition mode assays including isothermal titration calorimetry (ITC) disclosed that both compounds 3 and 5 exhibited a reversibly mixed inhibition on NDM-1, with a K i value of 1.9 and 10.8 μM, respectively. Antibacterial activity tests indicated that a dose of 64 μg·mL−1 Schiff bases resulted in 2–128-fold reduction in MICs of cefazolin on E. coli producing NDM-1 (except 4). Cytotoxicity assays showed that both Schiff bases 3 and 5 have low cytotoxicity on the mouse fibroblast (L929) cells at a concentration of up to 400 μM. Docking studies suggested that the hydroxyl group interacts with Gln123 and Glu152 of NDM-1, and the amino groups interact with the backbone amide groups of Glu152 and Asp223. This study provided a novel scaffold for the development of NDM-1 inhibitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • A compound library of fifty-two dithiocarbamates was constructed. • SA09-Cu exhibited promising synergistic inhibition on CREs. • SA09-Cu is a noncompetitive inhibitor of NDM-1. • SA09-Cu inactivated NDM-1 possibly by oxidizing the Zn(II)-thiolate site. The worldwide prevalence of NDM-1-producing Gram-negative pathogens has drastically undermined the clinical efficacy of carbapenems, prompting a need to devise an effective strategy to preserve their clinical value. Here we constructed a focused compound library of dithiocarbamates and systematically evaluated their potential synergistic antibacterial activities combined with copper. SA09-Cu exhibited excellent inhibition against a series of clinical NDM-1-producing carbapenem-resistant Enterobacteriaceae (CRE) in restoring meropenem effect, and slowed down the development of carbapenem resistance. Enzymatic kinetic and isothermal titration calorimetry studies demonstrated that SA09-Cu was a noncompetitive NDM-1 inhibitor. The electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) revealed a novel inhibition mechanism, which is that SA09-Cu could convert NDM-1 into an inactive state by oxidizing the Zn(II)-thiolate site of the enzyme. Importantly, SA09-Cu showed a unique redox tuning ability, and avoided to be reduced by intracellular thiols of bacteria. In vivo experiments indicated that SA09 combined with CuGlu could effectively potentiate MER's effect against NDM-1-producing E. coli (EC23) in the murine infection model. This study provides a highly promising scaffold in developing novel inhibitors to combat NDM-1-producing CREs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The novel thiosemicarbazones specifically inhibit NDM-1 and ImiS, with an IC 50 in the range of 0.37–21.35 and 0.45–8.76 μM. • The thiosemicarbazones alone sterilize resistant bacteria E. coli -ImiS and E. coli -NDM-1, with a MIC value in the scope of 8–128 μg/mL. • Partial thiosemicarbazones enhanced the antimicrobial activity of Meropenem on E. coli -ImiS and E. coli -NDM-1. • A thiosemicarbazone in combination with Meropenem significantly reduced the bacterial load in liver and spleen of mice. The superbug infection mediated by metallo-β-lactamases (MβLs) has grown into anemergent health threat, and development of MβL inhibitors is an ideal strategy to combat the infection. In this work, twenty-five thiosemicarbazones 1a - e , 2a - e , 3a - e , 4a - d, 5a-d and 6a-b were synthesized and assayed against MβLs ImiS, NDM-1 and L1. The gained molecules specifically inhibited NDM-1 and ImiS, exhibiting an IC 50 value in the range of 0.37–21.35 and 0.45–8.76 µM, and 2a was found to be the best inhibitor, with an IC 50 of 0.37 and 0.45 µM, respectively, using meropenem (MER) as substrate. Enzyme kinetics and dialysis tests revealed and confirmed by ITC that 2a is a time-and dose-dependent inhibitor of ImiS and NDM-1, it competitively and reversibly inhibited ImiS with a K i value of 0.29 µM, but irreversibly inhibited NDM-1. Structure-activity relationship disclosed that the substitute dihydroxylbenzene significantly enhanced inhibitory activity of thiosemicarbazones on ImiS and NDM-1. Most importantly, 1a - e , 2a - e and 3a - b alone more strongly sterilized E. coli -ImiS and E. coli -NDM-1 than the MER, displaying a MIC value in the range of 8–128 μg/mL, and 2a was found to be the best reagent with a MIC of 8 and 32 μg/mL. Also, 2a alone strongly sterilized the clinical isolates EC01, EC06-EC08, EC24 and K. pneumonia -KPC-NDM, showing a MIC value in the range of 16–128 μg/mL, and exhibited synergistic inhibition with MER on these bacteria tested, resulting in 8–32-fold reduction in MIC of MER. SEM images shown that the bacteria E. coli -ImiS, E. coli -NDM-1, EC24, K. pneumonia -KPC and K. pneumonia -KPC-NDM treated with 2a (64 μg/mL) suffered from distortion, emerging adhesion between individual cells and crumpled membranes. Mice tests shown that monotherapy of 2a evidently limited growth of EC24 cells, and in combination with MER, it significantly reduced the bacterial load in liver and spleen. Docking studies suggest that the 2,4-dihydroxylbenzene of 2a acts as zinc-binding group with the Zn(II) and the residual amino acids in CphA active center, tightly anchoring the inhibitor at active site. This work offered a promising scaffold for the development of MβLs inhibitors, specifically the antimicrobial for clinically drug-resistant isolates. [ABSTRACT FROM AUTHOR]

[Display omitted] • N -acylhydrazones reversibly and competitively inhibit NDM-1; • N -acylhydrazones synergize meropenem to exhibit antibacterial effect in vivo and in vitro ; • N -acylhydrazones have low cytotoxicity. The expression of β-lactamases, especially metallo-β-lactamases (MβLs) in bacteria is one of the main causes of drug resistance. In this work, an effective N -acylhydrazone scaffold as MβL inhibitor was constructed and characterized. The biological activity assays indicated that the synthesized N -acylhydrazones 1 – 11 preferentially inhibited MβL NDM-1, and 1 was found to be the most effective inhibitor with an IC 50 of 1.2 µM. Analysis of IC 50 data revealed a structure–activity relationship, which is that the pyridine and hydroxylbenzene substituents at 2-position improved inhibition of the compounds on NDM-1. ITC and enzyme kinetics assays suggested that it reversibly and competitively inhibited NDM-1 (K i = 0.29 ± 0.05 µM). The synthesized N -acylhydrazones showed synergistic antibacterial activities with meropenem, reduced 4–16-fold MIC of meropenem on NDM-1- producing E. coli BL21 (DE3), while 1 restored 4-fold activity of meropenem on K. pneumonia expressing NDM-1 (NDM- K. pneumoniae). The mice experiments suggested that 1 combined meropenem to fight against NDM- K. pneumoniae infection in the spleen and liver. Cytotoxicity assays showed that 1 and 2 have low cytotoxicity. This study offered a new framework for the development of NDM-1 inhibitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SARS-CoV-2 main protease is the target to combat COVID-19. • Ebsulfur and Ebselen strongly inhibited the main protease(IC 50 = 0.074-0.91 μM). • The Ebsulfur tightly and irreversibly bound the main protease by forming an S S bond. The emerging COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has raised a global catastrophe. To date, there is no specific antiviral drug available to combat this virus, except the vaccine. In this study, the main protease (Mpro) required for SARS-CoV-2 viral replication was expressed and purified. Thirty-six compounds were tested as inhibitors of SARS-CoV-2 Mpro by fluorescence resonance energy transfer (FRET) technique. The half-maximal inhibitory concentration (IC 50) values of Ebselen and Ebsulfur analogs were obtained to be in the range of 0.074–0.91 μM. Notably, the molecules containing furane substituent displayed higher inhibition against Mpro, followed by Ebselen 1i (IC 50 = 0.074 μM) and Ebsulfur 2k (IC 50 = 0.11 μM). The action mechanism of 1i and 2k were characterized by enzyme kinetics, pre-incubation and jump dilution assays, as well as fluorescent labeling experiments, which suggested that both compounds covalently and irreversibly bind to Mpro, while molecular docking suggested that 2k formed an S S bond with the Cys145 at the enzymatic active site. This study provides two very potent scaffolds Ebsulfur and Ebselen for the development of covalent inhibitors of Mpro to combat COVID-19. [ABSTRACT FROM AUTHOR]