Salicylaldoxime derivatives as new leads for the development of carbonic anhydrase inhibitors

Screening a library of potential competitive inhibitors against bacterial threonyl-tRNA synthetase: DFT calculations

Due to the growing interest in directing aminoacyl-tRNA synthetases for antimicrobial therapies, evaluating the binding proficiency of potential inhibitors against this target holds significant importance. In this work, we proposed potential ligands that could properly bind to the crucial Zn(II) cofactor located in the active site of Threonyl-tRNA synthetases (ThrRS), potentially functioning as competitive inhibitors. Initially, detailed DFT quantum chemical study was conducted to examine the binding ability of threonine against unnatural amino acids to cofactor Zn(II). Then, the binding energy value for each suggested ligand has been determined and compared to the value determined for the native substrate, threonine. Our screening investigation showed that the native threonine should coordinate in a bidentate fashion to this Zn(II) which lead to the highest (binding energy) BE Thereby, the synthetic site of ThrRS rejects unnatural amino acids that cannot afford this type of coordination to Zn(II) ion which has been supported by our calculations. Moreover, based on their binding to the Zn(II) and the obtained BE values compared to the cognate threonine, many potent ligands have been suggested. Importantly, ligands with deprotonated warheads showed the highest binding ability amongst a list of potential hits. Further investigation on the selected ligands using molecular docking and QM/MM calculations confirmed our findings of the suggested ligands being able to bind efficiently in the active site of ThrRS. The suggested hits from this study should be valuable in paving routs for developing candidates as competitive inhibitors against the bacterial ThrRS.Communicated by Ramaswamy H. Sarma.

Redetermination of the crystal structure of (E)-5-bromo-2-hydroxybenzaldehyde oxime, C 7 H 6 BrNO 2

C11H14ClNO, monoclinic, P21/c (no. 14), a = 14.48(2) Å, b = 3.956(6) Å, c = 13.765(19) Å, β = 99.266(15) ∘ , V = 778.4(19) Å 3 , Z = 4, R gt (F) = 0.0236, wR ref (F 2) = 0.0584, T = 296(2) K.

3-Functionalised benzenesulphonamide based 1,3,4-oxadiazoles as selective carbonic anhydrase XIII inhibitors: Design, synthesis and biological evaluation

A new series of benzenesulphonamide linked-1,3,4-oxadiazole hybrids (6a-s) has been synthesized and tested for their carbonic anhydrase inhibition against human (h) carbonic anhydrase (CA) isoforms hCA I, II, IX, and XIII. Fluorescence properties of some of the synthesized molecules were studied. Most of the molecules exhibited significant inhibitory power, comparable or better than the standard drug acetazolamide (AAZ) on hCA XIII. Out of 19 tested molecules, compound 6e (75.8 nM) was 3 times more potent than AAZ (250.0 nM) against hCA I, whereas compound 6e (15.4 nM), 6g (16.2 nM), 6h (16.4 nM) and 6i (17.0 nM) were found to be more potent than AAZ (17.0 nM) against isoform hCA XIII. It is anticipated that these compounds could be taken as the potential leads for the development of selective hCA XIII isoform inhibitors with improved potency.

Synthesis of a new series of 3-functionalised-1-phenyl-1,2,3-triazole sulfamoylbenzamides as carbonic anhydrase I, II, IV and IX inhibitors

The synthesis of a novel series of 3-functionalised benzenesulfonamides incorporating phenyl-1,2,3-triazole with an amide linker was achieved by using the "click-tail" approach. The new compounds, including the intermediates, were assayed as inhibitors of human carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA I and II (cytosolic isoforms) and also for hCA IV and IX (transmembrane isoforms) taking acetazolamide as standard drug. Most of these compounds exhibited excellent activity against all these isoforms. hCA I was inhibited with Kis in the range of 50.8-966.8 nM, while the glaucoma associated hCA II was inhibited with Kis in the range of 6.5-760.0 nM. Isoform hCA IV was inhibited with Kis in the range of 65.3-957.5 nM, whereas the tumor associated hypoxia induced hCA IX was inhibited with Kis in the range of 30.8-815.9 nM. The structure activity relationship study for the 3-functionalised-1-phenyl-1,2,3-triazole sulfamoylbenzamides against these isoforms was also inferred from the results.

Synthesis of novel isoindoline-1,3-dione-based oximes and benzenesulfonamide hydrazones as selective inhibitors of the tumor-associated carbonic anhydrase IX

The synthesis, characterization and biological evaluation of a library of isoindoline-1,3-dione-based oximes and benzenesulfonamide hydrazones is disclosed. The set of hydroxyiminoethyl aromatic derivatives 10-18 was designed to assess the potentiality as zinc-binder for a feebly studied functional group in the field of carbonic anhydrase (CA, EC 4.2.1.1) inhibition. Analogue phenylphthalimmides were linked to benzenesulfonamide scaffold by hydrazone spacers in the second subset of derivatives 20-28 to further investigate the application of the "tail approach" as tool to afford CA selective inhibition profiles. The compounds were assayed for the inhibition of physiologically relevant isoforms of human carbonic anhydrases (hCA, EC 4.2.1.1), the cytosolic CA I and II, and the membrane-bound CA IV and tumor-associated CA IX. The new zinc-binders, both of the oxime and sulfonamide types, showed a striking selective activity against the target hCA IX over ubiquitous hCA I and II, with diverse inhibitory ranges and ratio differing the two subsets. With CA IX being a strongly current antitumor/antimetastatic drug target, these series of compounds may be of interest for the development of new, both conventional and unconventional anticancer drugs targeting hypoxia-induced CA isoforms such as CA IX with minimum ubiquitous CAs-related side effects.

Dual-tail approach to discovery of novel carbonic anhydrase IX inhibitors by simultaneously matching the hydrophobic and hydrophilic halves of the active site

Dual-tail approach was employed to design novel Carbonic Anhydrase (CA) IX inhibitors by simultaneously matching the hydrophobic and hydrophilic halves of the active site, which also contains a zinc ion as part of the catalytic center. The classic sulfanilamide moiety was used as the zinc binding group. An amino glucosamine fragment was chosen as the hydrophilic part and a cinnamamide fragment as the hydrophobic part in order to draw favorable interactions with the corresponding halves of the active site. In comparison with sulfanilamide which is largely devoid of the hydrophilic and hydrophobic interactions with the two halves of the active site, the compounds so designed and synthesized in this study showed 1000-fold improvement in binding affinity. Most of the compounds inhibited the CA effectively with IC₅₀ values in the range of 7-152 nM. Compound 14e (IC₅₀: 7 nM) was more effective than the reference drug acetazolamide (IC₅₀: 30 nM). The results proved that the dual-tail approach to simultaneously matching the hydrophobic and hydrophilic halves of the active site by linking hydrophobic and hydrophilic fragments was useful for designing novel CA inhibitors. The effectiveness of those compounds was elucidated by both the experimental data and molecular docking simulations. This work laid a solid foundation for further development of novel CA IX inhibitors for cancer treatment.

Docking ligands into flexible and solvated macromolecules. 6. Development and application to the docking of HDACs and other zinc metalloenzymes inhibitors

Metalloenzymes are ubiquitous proteins which feature one or more metal ions either directly involved in the enzymatic activity and/or structural properties (i.e., zinc fingers). Several members of this class take advantage of the Lewis acidic properties of zinc ions to carry out their various catalytic transformations including isomerization or amide cleavage. These enzymes have been validated as drug targets for a number of diseases including cancer; however, despite their pharmaceutical relevance and the availability of crystal structures, structure-based drug design methods have been poorly and indirectly parametrized for these classes of enzymes. More specifically, the metal coordination component and proton transfers of the process of drugs binding to metalloenzymes have been inadequately modeled by current docking programs, if at all. In addition, several known issues, such as coordination geometry, atomic charge variability, and a potential proton transfer from small molecules to a neighboring basic residue, have often been ignored. We report herein the development of specific functions and parameters to account for zinc-drug coordination focusing on the above-listed phenomena and their impact on docking to zinc metalloenzymes. These atom-type-dependent but atomic charge-independent functions implemented into Fitted 3.1 enable the simulation of drug binding to metalloenzymes, considering an acid-base reaction with a neighboring residue when necessary with good accuracy.

Synthesis and characterization of some metal complexes of a proton transfer salt, and their inhibition studies on carbonic anhydrase isozymes and the evaluation of the results by statistical analysis

A novel proton transfer compound (HMeOABT)(+) (HDPC)(-) (1) and its Fe(III), Co(II), Ni(II) and Cu(II) complexes (2-5) have been prepared and characterized by spectroscopic techniques. Complex 4 has distorted octahedral conformation revealed by single crystal X-ray diffraction method. Structures of the other complexes might be proposed as octahedral according to experimental data. All compounds were also evaluated for their in vitro inhibition effects on hCA I and II for their hydratase and esterase activities. Although there is no inhibition for hydratase activities, all compounds have inhibited the esterase activities of hCA I and II. Data have been analyzed by using a one-way analysis of variance. The comparison of the inhibition studies of 1-5 to parent compounds indicates that 1-5 have superior inhibitory effects. The inhibition effects of 2-5 are also compared to inhibitory properties of the metal complexes of MeOABT and H2DPC, revealing an improved transfection profile.