Synthesis of different thio-scaffolds bearing sulfonamide with subnanomolar carbonic anhydrase II and IX inhibitory properties and X-ray investigations for their inhibitory mechanism

The dopamine D2 receptors antagonist Veralipride inhibits carbonic anhydrases: solution and crystallographic insights on human isoforms

The inhibitory effects of veralipride, a benzamide-class antipsychotic acting as dopamine D2 receptors antagonist incorporates a primary sulfonamide moiety and was investigated for its interactions with carbonic anhydrase (CA) isoforms. In vitro profiling using the stopped-flow technique revealed that veralipride exhibited potent inhibitory activity across all tested hCA isoforms, with exception of hCA III. Comparative analysis with standard inhibitors, acetazolamide (AAZ), and sulpiride, provided insights for understanding the relative efficacy of veralipride as CA inhibitor. The study reports the X-ray crystal structure analysis of the veralipride adduct with three human (h) isoforms, hCA I, II, and CA XII mimic, allowing the understanding of the molecular interactions rationalizing its inhibitory effects against each isoform. These findings contribute to our understanding of veralipride pharmacological properties and for the design of structural analogs endowed with polypharmacological properties.

Photoactivatable Heptamethine-Based Carbonic Anhydrase Inhibitors Leading to New Anti-Antibacterial Agents

With the aim to propose innovative antimicrobial agents able to not only selectively inhibit bacterial carbonic anhydrases (CAs) but also to be photoactivated by specific wavelengths, new heptamethine-based compounds decorated with a sulfonamide moiety were synthesized by means of different spacers. The compounds displayed potent CA inhibition and a slight preference for bacterial isoforms. Furthermore, minimal inhibitory and bactericidal concentrations and the cytotoxicity of the compounds were assessed, thus highlighting a promising effect under irradiation against S. epidermidis. The hemolysis activity test showed that these derivatives were not cytotoxic to human red blood cells, further corroborating their favorable selectivity index. This approach led to the discovery of a valuable scaffold for further investigations.

Vasodilation of Pre-contracted Porcine Retinal Arteries by Carbonic Anhydrase Inhibitors with Enhanced Lipophilicity

PURPOSE

In this study, we investigated the vasodilation properties on pre-contracted retinal arteries of a restricted series of carbonic anhydrase inhibitors (CAIs) of the sulfonamide type with enhanced lipophilicity, to assess if it affects the potency of CAIs as vasodilators.

METHODS

Carbonic anhydrase (CA) inhibition and in vitro kinetics of the compounds designed and synthesized for testing in this study were assessed by extracting human CA isoform proteins (hCA) from human cells expressing the isoforms of interest, and then measure the affinity of the novel compound for the hCAs by stopped-flow CO₂ hydrase spectroscopy. Lipophilicity of compounds was measured by obtaining their octanol-water partition coefficient, expressed as calculated logP. Porcine eyes were obtained from a local abattoir, and the wall tension of porcine retinal arteriole segments dissected from the eyes was measured with small wire vessel myography. The effects of the CA compounds on wall tension were assessed by adding them to the myography bath, after pre-contracting the vessel by prostaglandin analog U-46619.

RESULTS

All compounds induced vasodilation but at different concentrations. Among the tested compounds the most potent vasodilators were found to be the seleno-compound 4 and sulfur-ether compound 8 with EC₅₀ values of 7.13 × 10^-5 and 7.93 × 10^-5 M, respectively, whereas the remaining ones induced complete vasodilation at EC₅₀ comprised within the sub millimolar range.

CONCLUSIONS

All the data reported in this study (i.e. results from myography, in vitro kinetics and LogPs) confirm the important role played by several CA isoforms in vasodilation, although the precise mechanism of action still remains to be elucidated.

Novel benzenesulfonamide-bearing pyrazoles and 1,2,4-thiadiazoles as selective carbonic anhydrase inhibitors

Two series comprising 20 novel benzenesulfonamides bearing thioureido-linked pyrazole 8 and amino-1,2,4-thiadiazole 10 were synthesized and assayed as human carbonic anhydrase (hCA) inhibitors against isoforms I and II as well as the tumor-associated isoforms IX and XII. Molecular modeling studies of some potent derivatives (8a, 8c, 10a, and 10c) were also performed against isoforms hCA I, II, and XII. Both the promising series of compounds were synthesized by using commercially available mtethyl ketones and sulfanilamide as the starting materials. Interestingly, this paper also reports a novel methodology for the synthesis of amino-1,2,4-thiadiazoles 10 using 3-amino isoxazoles and 4-isothiocyanatobenzenesulfonamide as reactants. The activity profile of all the newly synthesized compounds reveals that amino-linked 1,2,4-thiadiazoles 10 were better inhibitors of the cytosolic isoform, hCA I, as compared to thioureido-linked pyrazoles 8. Further, hCA II was strongly inhibited by nearly all the newly synthesized sulfonamides, while all the compounds were less effective as hCA IX and XII inhibitors compared to the standard drug acetazolamide. However, in terms of selectivity, compound 8e was found to be the most selective inhibitor of hCA II, which is the isoform associated with glaucoma, edema, altitude sickness, and epilepsy.

Calixarenes Incorporating Sulfonamide Moieties: Versatile Ligands for Carbonic Anhydrases Inhibition

Carbonic anhydrases (CAs) continue to represent a relevant pharmaceutical target. The need of selective inhibitors and the involvement of these metalloenzymes in many multifaceted diseases boost the search for new ligands able to distinguish among the different CA isoforms, and for multifunctional systems simultaneously able to inhibit CAs and to interfere with other pathological events by interacting with additional targets. In this work, we successfully explored the possibility of preparing new CAs ligands by combining calixarenes with benzensulfonamide units. Inhibition tests towards three human CA isoforms evidenced, for some of the ligands, K_i values in the nanomolar range and promising selectivity. X-ray and molecular modeling studies provided information on the mode of binding of these calixarene derivatives. Thanks to the encouraging results and the structural features typical of the calixarene scaffold, it is then possible to plan for the future the design of multifunctional inhibitors for this class of widely spread enzymes.

Chalcogenides-incorporating carbonic anhydrase inhibitors concomitantly reverted oxaliplatin-induced neuropathy and enhanced antiproliferative action

Platinum-based chemotherapy is widely used for the treatment of different tumors but is associated with serious side effects, among which neuropathic pain. Carbonic anhydrase (CA, EC 4.2.1.1) inhibitors have recently been validated as therapeutic agents in neuropathic pain and as antitumor agents. We report the synthesis of new organochalcogenides bearing the benzensulfonamide moiety acting as potent inhibitors of several human CA isoforms and, in particular, against hCA II and VII endowed with potent neuropathic pain attenuating effects. Moreover, in combination with cisplatin or doxorubicin, some of the new CA inhibitors enhanced the effects of the anticancer drugs capability in counteracting breast cancer MCF7 cell viability. The concomitant anti-neuropathic pain and antiproliferative effects of the new chalcogenide-based CA inhibitors represent an innovative approach for the counteraction and management of side effects associated with clinically platinum drugs as antitumor agents.

Selective Inhibition of Helicobacter pylori Carbonic Anhydrases by Carvacrol and Thymol Could Impair Biofilm Production and the Release of Outer Membrane Vesicles

Helicobacter pylori, a Gram-negative neutrophilic pathogen, is the cause of chronic gastritis, peptic ulcers, and gastric cancer in humans. Current therapeutic regimens suffer from an emerging bacterial resistance rate and poor patience compliance. To improve the discovery of compounds targeting bacterial alternative enzymes or essential pathways such as carbonic anhydrases (CAs), we assessed the anti-H. pylori activity of thymol and carvacrol in terms of CA inhibition, isoform selectivity, growth impairment, biofilm production, and release of associated outer membrane vesicles-eDNA. The microbiological results were correlated by the evaluation in vitro of H. pylori CA inhibition, in silico analysis of the structural requirements to display such isoform selectivity, and the assessment of their limited toxicity against three probiotic species with respect to amoxicillin. Carvacrol and thymol could thus be considered as new lead compounds as alternative H. pylori CA inhibitors or to be used in association with current drugs for the management of H. pylori infection and limiting the spread of antibiotic resistance.

Novel insights on saccharin- and acesulfame-based carbonic anhydrase inhibitors: design, synthesis, modelling investigations and biological activity evaluation

A large library of saccharin and acesulfame derivatives has been synthesised and evaluated against four isoforms of human carbonic anhydrase, the two off-targets hCA I/II and the tumour related isoforms hCA IX/XII. Different strategies of scaffold modification have been attempted on both saccharin as well as acesulfame core leading to the obtainment of 60 compounds. Some of them exhibited inhibitory activity in the nanomolar range, albeit some of the performed changes led to either micromolar activity or to its absence, against hCA IX/XII. Molecular modelling studies focused the attention on the binding mode of these compounds to the enzyme. The proposed inhibition mechanism is the anchoring to zinc-bound water molecule. Docking studies along with molecular dynamics also underlined the importance of the compounds flexibility (e.g. achieved through the insertion of methylene group) which favoured potent and selective hCA inhibition.

Synthesis of novel tris-chalcones and determination of their inhibition profiles against some metabolic enzymes

In this study, we report the synthesis of novel tris-chalcones and testing of human carbonic anhydrase I, and II isoenzymes (hCA I, and hCA II), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and α-glycosidase (α-Gly) inhibitors for the development of novel chalcone structures towards for treatment of some diseases. The compounds demonstrated K_i values between 13.6 ± 1.1 and 50.0 ± 17.1 nM on hCA I, 9.9 ± 0.8 and 39.5 ± 15.1 nM on hCA II, 3.1 ± 0.2 and 20.1 ± 1.9 nM on AChE, 4.9 ± 0.4 and 14.7 ± 5.2 nM on BChE and 3.9 ± 0.2 and 22.4 ± 10.7 nM on α-Gly enzymes. The results revealed that novel tris-chalcones can have promising drug potential for glaucoma, leukaemia, epilepsy; Alzheimer's disease that was associated with the high enzymatic activity of hCA I, hCA II, AChE, and BChE enzymes.

Dual Carbonic Anhydrase IX/XII Inhibitors and Carbon Monoxide Releasing Molecules Modulate LPS-Mediated Inflammation in Mouse Macrophages

Low concentrations of carbon monoxide (CO) were reported to exhibit anti-inflammatory effects when administered in cells by suitable chemotypes such as CO releasing molecules (CO-RMs). In addition, the pH-modulating abilities of specific carbonic anhydrase isoforms played a crucial role in different models of inflammation and neuropathic pain. Herein, we report a series of chemical hybrids consisting of a Carbonic Anhydrase (CA) inhibitor linked to a CO-RM tail (CAI/CO-RMs). All compounds and their precursors were first tested in vitro for their inhibition activity against the human CA I, II, IX, and XII isoforms as well their CO releasing properties, aiming at corroborating the data by means of molecular modelling techniques. Then, their impact on metabolic activity modulation of RAW 264.7 mouse macrophages for 24 and 48 h was assessed with or without lipopolysaccharide (LPS) stimulation. The compounds were shown to counteract the inflammatory stimulus as also indicated by the reduced tumor necrosis factor alpha (TNF-α) release after treatment. All the biological results were compared to those of N-acetylcysteine (NAC) as a reference antioxidant compound. Within the series, two CAI/CO-RM hybrids (1 and 2), bearing both the well-known scaffold able to inhibit CAs (acesulfame) and the cobalt-based CO releasing portion, induced a higher anti-inflammatory effect up to 48 h at concentrations lower than NAC.

Synthesis, Computational Studies and Assessment of in Vitro Activity of Squalene Derivatives as Carbonic Anhydrase Inhibitors

We report novel molecules incorporating the nontoxic squalene scaffold and different carbonic anhydrase inhibitors (CAIs). Potent inhibitory action, in the low-nanomolar range, was detected against isoforms hCA II for sulfonamide derivatives, which proved to be selective against this isoform over the tumor-associate hCA IX and XII isoforms. On the other hand, coumarin derivatives showed weak potency but high selectivity against the tumor-associated isoform CA IX. These compounds are interesting candidates for preclinical evaluation in glaucoma or various tumors in which the two enzymes are involved. In addition, an in silico study of inhibitor-bound hCA II revealed extensive interactions with the hydrophobic pocket of the active site and provided molecular insights into the binding properties of these new inhibitors.

Azidothymidine "Clicked" into 1,2,3-Triazoles: First Report on Carbonic Anhydrase-Telomerase Dual-Hybrid Inhibitors

Cancer cells rely on the enzyme telomerase (EC 2.7.7.49) to promote cellular immortality. Telomerase inhibitors (i.e., azidothymidine) can represent promising antitumor agents, although showing high toxicity when administered alone. Better outcomes were observed within a multipharmacological approach instead. In this context, we exploited the validated antitumor targets carbonic anhydrases (CAs; EC 4.2.1.1) IX and XII to attain the first proof of concept on CA–telomerase dual-hybrid inhibitors. Compounds 1b, 7b, 8b, and 11b showed good in vitro inhibition potency against the CAs IX and XII, with K_I values in the low nanomolar range, and strong antitelomerase activity in PC-3 and HT-29 cells (IC₅₀ values ranging from 5.2 to 9.1 μM). High-resolution X-ray crystallography on selected derivatives in the adduct with hCA II as a model study allowed to determine their binding modes and thus to set the structural determinants necessary for further development of compounds selectively targeting the tumoral cells.

Synthetic Strategies and Computational Inhibition Activity Study for Triazinyl-Substituted Benzenesulfonamide Conjugates with Polar and Hydrophobic Amino Acids as Inhibitors of Carbonic Anhydrases

Various sulfonamide derivatives are intensively studied as anticancer agents owing to their inhibitory activity against human tumor-associated carbonic anhydrase isoforms. In this work, different synthetic procedures for the series of 1,3,5-triazinyl-aminobenzenesulfonamide conjugates with amino acids, possessing polar uncharged, negatively charged, and hydrophobic side chain, were studied and optimized with respect to the yield/purity of the synthesis/product as well as the time of synthetic reaction. These procedures were compared to each other via characteristic HPLC-ESI-DAD/QTOF/MS analytical product profiles, and their benefits as well as limitations were discussed. For new sulfonamide derivatives, incorporating s-triazine with a symmetric pair of polar and some less-polar proteinogenic amino acids, inhibition constants (KIs) against four human carboanhydrases (hCAs), namely cytosolic hCA I, II, transmembrane hCA IV, and the tumor-associated, membrane-bound hCA IX isoforms, were computationally predicted applying various methods of the advanced statistical analysis. Quantitative structure-activity relationship (QSAR) analysis indicated an impressive KI ratio (hCA II/hCA IX) 139.1 and hCA IX inhibition constant very similar to acetazolamide (KI = 29.6 nM) for the sulfonamide derivative disubstituted with Gln. The derivatives disubstituted with Ser, Thr, and Ala showed even lower KIs (8.7, 13.1, and 8.4 nM, respectively).

Continued exploration and tail approach synthesis of benzenesulfonamides containing triazole and dual triazole moieties as carbonic anhydrase I, II, IV and IX inhibitors

A library of twenty two novel 1,2,3-triazole benzenesulfonamides incorporating thiosemicarbazide, 5(4H)-thione-1,2,4-triazole and variously substituted phenacyl appended 1,2,4-triazole as tail were designed, synthesized and assessed for their efficacy as inhibitors against carbonic anhydrase human (h) isoforms hCA I, II, IV and IX. The physiologically important and off-target cytosolic isoform hCA I was weakly inhibited by most of the newly synthesized sulfonamides while the glaucoma associated isoform hCA II was moderately inhibited with KIs spanning in low nanomolar range (KI = 8.0 nM-0.903 μM). The membrane bound isoform hCA IV, which is known to be involved in glaucoma and retinitis pigmentosa among others, was strongly inhibited by all newly synthesized sulfonamides out of which nine compounds inhibited isoform hCA IV even more effectively as compared to standard drug acetazolamide (AAZ). The membrane bound isoform hCA IX, associated with growth of tumor cells, was moderately inhibited with KIs ranging between 51 nM-3.198 μM. The effect of appending variously substituted tails on heterocyclic moieties over inhibition potential of synthesized sulfonamides is also disclosed which can be of further interest in pharmacological studies for exploring synthesis of isoform selective inhibitors.

Synthesis of novel tellurides bearing benzensulfonamide moiety as carbonic anhydrase inhibitors with antitumor activity

We have synthetized a novel series of β-hydroxy tellurides bearing the benzenesulfonamide group as potent inhibitors of carbonic anhydrase enzymes. In a one pot procedure, we discovered both the ring opening reaction of the three-membered ring and the cleavage of the sulfonamide protecting moiety at the same time. Moreover, the first X-ray co-crystallographic structure of a β-hydroxy telluride derivative with hCA II is reported. The potent effects of these compounds against the tumor-associated hCA IX with low nanomolar constant inhibition values give the possibility to evaluate their activity in vitro using a breast cancer cell line (MDA-MB-231). Compounds 7e and 7g induced significant toxic effects against tumor cells after 48 h incubation in normoxic conditions killing over 50% of tumor cells at 3 μM, but their efficacy decreased in hypoxic conditions reaching the 50% of the tumor cell viability only at 30 μM. These unusual features make them interesting lead compounds to act as antitumor agents, not only as Carbonic Anhydrase IX inhibitors, but reasonably in different pathways, where hCA IX is not overexpressed.

Syntesis of thio- and seleno-acetamides bearing benzenesulfonamide as potent inhibitors of human carbonic anhydrase II and XII

A novel series of thio- and seleno-acetamides bearing benzenesulfonamide were synthetized and tested as human carbonic anhydrase inhibitors. These compounds were tested for the inhibition of four human (h) isoforms, hCA I, II, IX, and XII, involved in pathologies such as glaucoma (CA II and XII) or cancer (CA IX/XII). Several derivatives showed potent inhibition activity in low nanomolar range such as 3a, 4a, 7a and 8a. Furthermore, based on the tail approach we explain the interesting and selective inhibition profile of compound such as 5a and 9a, which were more selective for hCA I, 9b which was selective for hCA II, 3f selective for hCA IX and finally, 3e and 4b selective for hCA XII, over the other three isoforms. They are interesting leads for the development of more effective and isoform-selective inhibitors.

Synthesis and Evaluation of Carbonic Anhydrase Inhibitors with Carbon Monoxide Releasing Properties for the Management of Rheumatoid Arthritis

Carbon monoxide (CO) is a gas endogenously produced in humans, reported to exhibit anti-inflammatory and cytoprotective effects at low concentration. In this context, CO releasing molecules (CORMs) are attracting enormous interest. Herein, we report a series of small-molecule hybrids consisting of a carbonic anhydrase (CA; EC 4.2.1.1) inhibitor linked to a CORM tail section (CAI-CORMs). All compounds were screened in vitro for their inhibition activity against the human (h) CA I, II, IV, IX, and XII isoforms. On selected CAI-CORM hybrids, the CO releasing properties were evaluated, along with their pain-relieving effect, in a model of rheumatoid arthritis. One CAI-CORM hybrid (5b) induced a higher pain-relieving effect compared to the one exerted by the single administration of CAI (5a) and CORM (15b) fragments, shedding light on the possibility to enhance the pain relief effect of CA inhibitors inserting a CO releasing moiety on the same molecular scaffold.

Sulfonamides incorporating piperazine bioisosteres as potent human carbonic anhydrase I, II, IV and IX inhibitors

Starting from the molecular simplification of (R) 4-(3,4-dibenzylpiperazine-1-carbonyl)benzenesulfonamide 9a, a compound endowed with selectivity for human Carbonic Anhydrase (hCA) IV, a series of piperazines and 4-aminopiperidines carrying a 4-sulfamoylbenzamide moiety as Zn-binding group have been designed and tested on human isoforms hCA I, II, IV and IX, using a stopped flow CO₂ hydrase assay. The aim of the work was to derive structure-activity relationships useful for designing isoform selective compounds. These structural modifications changed the selectivity profile of the analogues from hCA IV to hCA I and II, and improved potency. Several of the new compounds showed subnanomolar activity on hCA II. X-ray crystallography of ligand-hCAII complexes was used to compare the binding modes of the new piperazines and the previously synthesized 2-benzyl-piperazine analogues, explaining the inhibition profiles.

Ditocopheryl Sulfides and Disulfides: Synthesis and Antioxidant Profile

Symmetrical ditocopheryl disulfides (Toc)₂ S₂ and symmetrical and unsymmetrical ditocopheryl sulfides (Toc)₂ S were simply prepared under remarkably mild conditions with complete control of the regiochemistry by using δ-, γ-, and β-tocopheryl-N-thiophthalimides (Toc-NSPht) as common starting materials. The roles of sulfur atom(s), H-bond and aryl ring substitution pattern on the antioxidant profile of these new compounds, which were assembled by linking together two tocopheryl units, are also discussed.

Towards New Catalytic Antioxidants: A Simple and Mild Synthesis of Selenenylsulfides

A new methodology for the synthesis of small molecules containing the S-Se bond is reported. Aryl- and alkyl-selenols react smoothly with N-thiophthalimides to afford the corresponding selenenylsulfides through a clean SN2 path occurring at the sulfur atom. The reaction proceeds under very mild conditions in DMF in absence of catalysts for most of the substrates. The scope of the reaction was found to be broad, allowing a wide series of selenols and N-thiophtalimides to be efficiently employed in this procedure. Owing to the instability of the S-Se bond, selenenylsulfides exhibited a remarkable tendency to disproportionate to the corresponding symmetric diselenides and disulfides. Preliminary evaluation of the catalytic antioxidant properties of novel selenenylsulfides showed their behaviour as GPx mimics.

Selenols: a new class of carbonic anhydrase inhibitors

Stable aryl selenols were obtained through a convenient procedure. Selenols represent a new chemotype acting as carbonic anhydrase inhibitors (CAIs), inhibiting four human isoforms, CAs I, II, VII and the tumor-associated CA IX. X-ray crystallographic, physical and computational studies provided insights into the binding mode of this conceptually new class of CAIs.

Direct biocatalysed synthesis of first sulfur-, selenium- and tellurium- containing l-ascorbyl hybrid derivatives with radical trapping and GPx-like properties

6-O-l-Ascorbyl selenoesters, thioesters and telluroesters can be efficiently and directly prepared from l-ascorbic acid and suitable functionalised chalcogenoesters through lipase-catalysed transesterification reactions.

Mild and selective silicon-mediated access to enantioenriched 1,2-mercaptoamines and β-amino arylchalcogenides

Metal-free ring opening reactions of activated and unactivated aziridines with different silyl chalcogenides are described.

Ring opening reactions of heterocycles with selenium and tellurium nucleophiles

An overview of the preparation and synthetic potentialities of functionalized organoselenium and organotellurium compounds is presented.