Hydroxamic acid with benzenesulfonamide: An effective scaffold for the development of broad-spectrum metallo-β-lactamase inhibitors

Synthesis and Anticancer Potential of New Hydroxamic Acid Derivatives as Chemotherapeutic Agents

Histone deacetylase (HDAC) inhibitors have been shown to induce differentiation, cell cycle arrest, and apoptosis due to their low toxicity, inhibiting migration, invasion, and angiogenesis in many cancer cells. Studies show that hydroxamic acids are generally used as anticancers. For this reason, it is aimed to synthesize new derivatives of hydroxamic acids, to examine the anticancer properties of these candidate inhibitors, and to investigate the inhibition effects on some enzymes that cause multidrug resistance in cancer cells. For this reason, new (4-amino-2-methoxy benzohydroxamic acid (a), 4-amino-3-methyl benzohydroxamic acid (b), 3-amino-5-methyl benzohydroxamic acid (c)) amino benzohydroxamic acid derivatives were synthesized in this study. The effects on healthy fibroblast, lung (A549), and cervical (HeLa) cancer cells were investigated. In addition, their effects on TRXR1, GST, and GR activities, which are important for the development of chemotherapeutic strategies, were also examined. It was determined that molecule b was the most effective molecule in HeLa cancer cells with the lowest IC₅₀ value of 0.54. It was determined that molecule c was the most effective molecules for A549 and HeLa cancer cells, with the lowest IC₅₀ values of 0.78 mM and 0.25 mM, respectively. It was determined that b and c molecules directed cancer cells to necrosis rather than apoptosis. c molecule showed anticancer effect in A549 and HeLa cancer cells. It was found that molecule c significantly suppressed both GR and TRXR1 activities. In GST activities, however, inhibitors did not have a significant effect on cancer cells.

Hydroxamate and thiosemicarbazone: Two highly promising scaffolds for the development of SARS-CoV-2 antivirals

The emerging COVID-19 pandemic generated by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has severely threatened human health. The main protease (Mpro) of SARS-CoV-2 is promising target for antiviral drugs, which plays a vital role for viral duplication. Development of the inhibitor against Mpro is an ideal strategy to combat COVID-19. In this work, twenty-three hydroxamates 1a-i and thiosemicarbazones 2a-n were identified by FRET screening to be the potent inhibitors of Mpro, which exhibited more than 94% (except 1c) and more than 69% inhibition, and an IC50 value in the range of 0.12-31.51 and 2.43-34.22 μM, respectively. 1a and 2b were found to be the most effective inhibitors in the hydroxamates and thiosemicarbazones, with an IC50 of 0.12 and 2.43 μM, respectively. Enzyme kinetics, jump dilution and thermal shift assays revealed that 2b is a competitive inhibitor of Mpro, while 1a is a time-dependently inhibitor; 2b reversibly but 1a irreversibly bound to the target; the binding of 2b increased but 1a decreased stability of the target, and DTT assays indicate that 1a is the promiscuous cysteine protease inhibitor. Cytotoxicity assays showed that 1a has low, but 2b has certain cytotoxicity on the mouse fibroblast cells (L929). Docking studies revealed that the benzyloxycarbonyl carbon of 1a formed thioester with Cys145, while the phenolic hydroxyl oxygen of 2b formed H-bonds with Cys145 and Asn142. This work provided two promising scaffolds for the development of Mpro inhibitors to combat COVID-19.

Dihydroxyphenyl-substituted thiosemicarbazone: A potent scaffold for the development of metallo-β-lactamases inhibitors and antimicrobial

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 IC₅₀ 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 IC₅₀ 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.

Hydroxamates as a potent skeleton for the development of metallo-β-lactamase inhibitors

Bacterial resistance caused by metallo-β-lactamases (MβLs) has become an emerging public health threat, and the development of MβLs inhibitor is an effective way to overcome the resistance. In this study, thirteen novel O-aryloxycarbonyl hydroxamates were constructed and assayed against MβLs. The obtained molecules specifically inhibited imipenemase-1 (IMP-1) and New Delhi metallo-β-lactamase-1, exhibiting an IC₅₀ value in the range of 0.10-18.42 and 0.23-22.33 μM, respectively. The hydroxamate 5 was found to be the most potent inhibitor, with an IC₅₀ of 0.1 and 0.23 μM using meropenem and cefazolin as substrates. ICP-MS analysis showed that 5 did not coordinate to the Zn(II) ions at the active site of IMP-1, while the rapid dilution, thermal shift and MALDI-TOF assays revealed that the hydroxamate formed a covalent bond with the enzyme. Cytotoxicity assays indicated that the hydroxamates have low toxicity in MCF-7 cells. This work provided a potent scaffold for the development of MβLs inhibitors.

Dipyridyl-substituted thiosemicarbazone as a potent broad-spectrum inhibitor of metallo-β-lactamases

To combat the superbug infection caused by metallo-β-lactamases (MβLs), a dipyridyl-substituted thiosemicarbazone (DpC), was identified to be the broad-spectrum inhibitor of MβLs (NDM-1, VIM-2, IMP-1, ImiS, L1), with an IC₅₀ value in the range of 0.021-1.08 µM. It reversibly and competitively inhibited NDM-1 with a K_i value of 10.2 nM. DpC showed broad-spectrum antibacterial effect on clinical isolate K. pneumonia, CRE, VRE, CRPA and MRSA, with MIC value ranged from 16 to 32 µg/mL, and exhibited synergistic antibacterial effect with meropenem on MβLs-producing bacteria, resulting in a 2-16-, 2-8-, and 8-fold reduction in MIC of meropenem against EC-MβLs, EC01-EC24, K. pneumonia, respectively. Moreover, mice experiments showed that DpC also had synergistic antibacterial action with meropenem. In this work, DpC was identified to be a potent scaffold for the development of broad-spectrum inhibitors of MβLs.