Synthesis of new 3-(2-mercapto-4-oxo-4H-quinazolin-3-yl)-benzenesulfonamides with strong inhibition properties against the tumor associated carbonic anhydrases IX and XII

We report a series of novel metanilamide-based derivatives 3a–q bearing the 2-mercapto-4-oxo-4H-quinazolin-3-yl moiety as tail. All compounds were synthesized by means of straightforward condensation procedures and were investigated in vitro for their inhibition potency against the human (h) carbonic anhydrase (CA; EC 4.2.1.1.1) isoforms I, II, IX and XII. Among all compounds tested the 6-iodo 3g and the 7-fluoro 3i derivatives were the most potent inhibitors against the tumor associated CA IX and XII isoform (K_Is 1.5 and 2.7 nM respectively for the hCA IX and K_Is 0.57 and 1.9 nM respectively for the hCA XII).The kinetic data reported here strongly support compounds of this type for their future development as radiotracers in tumor pathologies which are strictly dependent on the enzymatic activity of the hCA IX and XII isoforms.     

Synthesis and biological evaluation of novel tris-chalcones as potent carbonic anhydrase,acetylcholinesterase, butyrylcholinesterase and α-glycosidase inhibitors

A novel class of fluoro-substituted tris-chalcones derivatives (5a-5i) was synthesized from phloroglucinol and corresponding benzaldehydes. A three step synthesis method was followed for the production of these tris-chalcone compounds. The structures of the newly synthesized compounds (5a-5i) were confirmed on the basis of IR, ¹H NMR, ¹³C NMR, and elemental analysis. The compounds’ inhibitory activities were tested against human carbonic anhydrase I and II isoenzymes (hCA I and hCA II), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and α-glycosidase (α-Gly). These chalcone derivatives had K_i values in the range of 19.58–78.73 nM for hCA I, 12.23–41.70 nM for hCA II, 1.09–6.84 nM for AChE, 8.30–32.30 nM for BChE and 0.93 ± 0.20–18.53 ± 5.06 nM against α-glycosidase. These results strongly support the promising nature of the tris-chalcone scaffold as selective carbonic anhydrase, acetylcholinesterase, butyrylcholinesterase, and α-glycosidase inhibitor. Overall, due to these derivatives’ inhibitory potential on the tested enzymes, they are promising drug candidates for the treatment of diseases like glaucoma, leukemia, epilepsy; Alzheimer’s disease; type-2 diabetes mellitus that are associated with high enzymatic activity of carbonic anhydrase, acetylcholine esterase, butyrylcholinesterase, and α-glycosidase.     

Synthesis and exploration of 2-morpholino-4-phenylthiazol-5-yl acrylamide derivatives for their effects against carbonic anhydrase I,II, IX and XII isoforms as a non-sulfonamide class of inhibitors

Novel series of 2-morpholino-4-phenylthiazol-5-yl acrylamide derivatives (8a–s) have been synthesized and explored as a non-sulfonamide class of carbonic anhydrase (CA, EC 4.2.1.1) inhibitors. The newly synthesized molecules were evaluated for their CA inhibitory potency against four isoforms: the cytosolic isozyme hCA I, II as well as trans-membrane tumor associated isoform hCA IX and hCA XII taking acetazolamide (AAZ) as standard drug. The results revealed that most of the compounds showed good activity against hCA II, IX, and XII whereas none of them were active against hCA I (K_i >100 μM). It is observed that the physiologically most important cytosolic isoform hCA II was inhibited by these molecules in the range of K_i 9.3–77.7 μM. It is also found the both the transmembrane isoforms hCA IX and XII were also inhibited with K_is ranging between 54.7–96.7 μM and 4.6–8.8 μM, respectively. The binding modes of the active compounds within the catalytic pockets of hCA II, IX and XII were evaluated by docking studies. This new non-sulfonamide class of selective inhibitors of hCA II, IX and XII over the hCA I isoform may be used for further understanding the physiological roles of some of these isoforms in various pathologies.     

Carbonic anhydrase inhibitors: Synthesis and inhibition of the human carbonic anhydrase isoforms I,II, IX and XII with benzene sulfonamides incorporating 4- and 3-nitrophthalimide moieties

A series of 4 and 5 nitro-1,3-dioxoisoindolin-2-yl benzenesulfonamide derivatives (compounds 1–8) was synthesized by reaction of benzenesulfonamide derivatives with 4 and 3-nitrophthalic anhydrides. These new sulfonamides were investigated as inhibitors of the zinc metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) and more specifically against the human (h) cytosolic isoforms hCA I and II and the transmembrane, tumor-associated hCA IX and XII. Most of the novel compounds were medium potency-weak hCA I inhibitors (K_is in the range of 295–10,000 nM), but were more effective hCA II inhibitors (K_is of 1.7–887 nM). The tumor-associated hCA IX was also inhibited, with K_is in the micromolar range, whereas against hCA XII the inhibition constants were in the range of 90–3746 nM. The structure–activity relationship (SAR) with this series of sulfonamides is straightforward, with the main features leading to good activity for each isoforms being established. The high sequence hCA alignment homology and molecular docking studies was performed in order to rationalize the activities reported and binding mode to different hCA as inhibitors.     

Discovery of new potent inhibitors for carbonic anhydrase IX by structure-based virtual screening

Through structure-based virtual screening, some dozen of benzene sulfonamides with novel scaffolds are identified as potent inhibitors against carbonic anhydrase (CA) IX with IC₅₀ values ranging from 2.86 to 588.34 nM. Among them, compounds 1 and 9 show high selectivity against tumor-target CA IX over CA II (the selectivity ratios are 21.3 and 136.6, respectively). The possible binding poses of hit compounds are also explored and the selectivity is elucidated by molecular docking simulations. The hit compounds discovered in this work would provide novel scaffolds for further hit-to-lead optimization.     

Inhibition Profiles of Some Symmetric Sulfamides Derived from Phenethylamines on Human Carbonic Anhydrase I,and II Isoenzymes

In this work, the inhibitory effect of some symmetric sulfamides derived from phenethylamines were determined against human carbonic anhydrase (hCA) I, and II isoenzymes, and compared with standard compound acetazolamide. IC₅₀ values were obtained from the Enzyme activity (%)-[Symmetric sulfamides] graphs. Also, K_i values were calculated from the Lineweaver-Burk graphs. Some symmetric sulfamides compounds ( 11 – 18 ) demonstrated excellent inhibition effects against hCA I, and II isoenzymes. These compounds demonstrated effective inhibitory profiles with IC₅₀ values in ranging from 21.66–28.88 nM against hCA I, 14.44–30.13 nM against hCA II. Among these compounds, the best K_i value for hCA I (K_i: 8.34±1.60 nM) and hCA II (K_i: 16.40±1.00 nM) is compound number 11 . Besides, the IC₅₀ value of acetazolamide used as a standard was determined as hCA I, hCA II 57.75 nM, 49.50 nM, respectively. Moreover, in silico ADME-Tox study showed that all synthesized compounds ( 11 – 18 ) had good oral bioavailability in light of Jorgensen's rule of three, and of Lipinski's rule of five.     

Synthesis and inhibitory properties of some carbamates on carbonic anhydrase and acetylcholine esterase

A series of carbamate derivatives were synthesized and their carbonic anhydrase I and II isoenzymes and acetylcholinesterase enzyme (AChE) inhibitory effects were investigated. All carbamates were synthesized from the corresponding carboxylic acids via the Curtius reactions of the acids with diphenyl phosphoryl azide followed by addition of benzyl alcohol. The carbamates were determined to be very good inhibitors against for AChE and hCA I, and II isoenzymes. AChE inhibition was determined in the range 0.209–0.291?nM. On the other hand, tacrine, which is used in the treatment of Alzheimer’s disease possessed lower inhibition effect (K_i: 0.398?nM). Also, hCA I and II isoenzymes were effectively inhibited by the carbamates, with inhibition constants (K_i) in the range of 4.49–5.61?nM for hCA I, and 4.94–7.66?nM for hCA II, respectively. Acetazolamide, which was clinically used carbonic anhydrase (CA) inhibitor demonstrated K_i values of 281.33?nM for hCA I and 9.07?nM for hCA II. The results clearly showed that AChE and both CA isoenzymes were effectively inhibited by carbamates at the low nanomolar levels.     

Evaluation of antimicrobial,antibiofilm and carbonic anhydrase inhibition profiles of 1,3‐bis‐chalcone derivatives

A series of 1,3‐bis‐chalcone derivatives ( 3a‐i, 6a‐i and 8 ) were synthesized and evaluated antimicrobial, antibiofilm and carbonic anhydrase inhibition activities. In this evaluation, 6f was found to be the most active compound showing the same effect as the positive control against Bacillus subtilis and Streptococcus pyogenes in terms of antimicrobial activity. Biofilm structures formed by microorganisms were damaged by compounds at the minimum inhibitory concentration value between 0.5% and 97%.1,3‐bis‐chalcones ( 3a‐i, 6a‐i and 8 ) showed good inhibitory action against human (h) carbonic anhydrase (CA) isoforms I and II. hCA I and II were effectively inhibited by these compounds, with K _i values in the range of 94.33 ± 13.26 to 787.38 ± 82.64 nM for hCA I, and of 100.37 ± 11.41 to 801.76 ± 91.11 nM for hCA II, respectively. In contrast, acetazolamide clinically used as CA inhibitor showed K _i value of 1054.38 ± 207.33 nM against hCA I, and 983.78 ± 251.08 nM against hCA II, respectively.     

Synthesis and biological evaluation of coumarin-1,3,4-oxadiazole hybrids as selective carbonic anhydrase IX and XII inhibitors

With an aim to develop novel heterocyclic hybrids as potent anticancer agents, we synthesized a series of coumarin-1,3,4-oxadiazole hybrids (7a-t) and evaluated for their inhibitory activity against the four physiologically relevant human carbonic anhydrase (hCA, EC 4.2.1.1) isoforms CA I, CA II, CA IX and CA XII. The CA inhibition results clearly indicated that the coumarin-1,3,4-oxadiazole derivatives (7a-t) exhibited selective inhibition of the tumor associated isoforms, CA IX and CA XII over CA I and II isoforms. Among all, compound 7b, exhibited significant inhibition in lower micromolar potency against hCA XII, with a K_i of 0.16 µM and compound 7n, exhibited significant inhibition in lower micromolar potency against hCA IX, with a K_i of 2.34 µM respectively. Therefore, compound 7b and 7n could be the potential leads for development of selective anticancer agents by exhibiting a novel mechanism of action through hCA IX and XII inhibition.     

1H‐indazole molecules reduced the activity of human erythrocytes carbonic anhydrase I and II isoenzymes

Carbonic anhydrase (CA) is an important metabolic enzyme family closely related to many physiological and pathological processes. Currently, carbonic anhydrase inhibitors are the target molecules in the treatment and diagnosis of many diseases. In present study, we investigated the inhibitory effects of some indazole molecules on the CA‐I and CA‐II isoenzymes isolated from human erythrocytes. We showed that human CA‐I and CA‐II activities were reduced by of some indazoles at low concentrations. IC₅₀ values, K_i constants, and inhibition types for each indazole molecule were determined. The indazoles showed K_i constants in a range of 0.383 ± 0.021 to 2.317 ± 0.644 mM, 0.409 ± 0.083 to 3.030 ± 0.711 mM against CA‐I and CA‐II, respectively. Each indazole molecule exhibited a noncompetitive inhibition effect. Bromine‐ and chlorine‐bonded indazoles were found to be more potent inhibitory effects on carbonic anhydrase isoenzymes. In conclusion, we conclude that these results may be useful in the synthesis of carbonic anhydrase inhibitors.     

Design,synthesis and antiproliferative activity evaluation of a series of pyrrolo[2,1-f][1,2,4]triazine derivatives

A series of 6-aminocarbonyl pyrrolo[2,1-f][1,2,4]triazine derivatives were designed by scaffold hopping strategy. The IC₅₀ values of compound 14a against PI3Ks were measured, showing selective activity against p110α and p110δ with IC₅₀s of 122 nM and 119 nM respectively. All the synthesized compounds were evaluated for their antiproliferative activity against human cancer cells by SRB assay. Compounds 14a, 14p and 14q exhibited potent antiproliferative activity against five types of human cancer cells and the PK property of 14q was also investigated here.     

Effects of dopaminergic compounds on carbonic anhydrase isozymes I,II, and VI

Studies on carbonic anhydrase (CA, EC 4.2.1.1) inhibitors have increased due to several therapeutic applications while there are few investigations on activators. Here we investigated CA inhibitory and activatory capacities of a series of dopaminergic compounds on human carbonic anhydrase (hCA) isozymes I, II, and VI. 2-Amino-1,2,3,4-tetrahydronaphthalene-6,7-diol hydrobromide and 2-amino-1,2,3,4-tetrahydronaphthalene-5,6-diol hydrobromide were found to show effective inhibitory action on hCA I and II whereas 2-amino-5,6-dibromoindan hydrobromide and 2-amino-5-bromoindan hydrobromide exhibited only moderate inhibition against both isoforms, being more effective inhibitors of hCA VI. K_i values of the molecules 3–6 were in the range of 41.12–363 μM against hCA I, of 0.381–470 μM against hCA II and of 0.578–1.152 μM against hCA VI, respectively. Compound 7 behaved as a CA activator with K_A values of 27.3 μM against hCA I, of 18.4 μM against hCA II and of 8.73 μM against hCA VI, respectively.     

Synthesis and comparative carbonic anhydrase inhibition of new Schiff’s bases incorporating benzenesulfonamide,methanesulfonamide, and methylsulfonylbenzene scaffolds

Herein, we report the synthesis, characterization, and carbonic anhydrase (CA) inhibition of the newly synthesized Schiff’s bases 4–18 with benzenesulfonamide, methanesulfonamide, and methylsulfonylbenzene scaffolds. The compound inhibition profiles against human CA (hCA) isoforms I, II, IX, and XII were compared to those of the standard inhibitors, acetazolamide (AAZ) and SLC-0111 (a CA inhibitor in Phase II clinical trials for the treatment of hypoxic tumors). The hCA I was inhibited by compounds 4a–8a with inhibition constants (K_I) in the range 93.5–428.1 nM (AAZ and SLC-0111: K_I, 250.0 and 5080.0 nM, respectively). Compounds 4a–8a proved to be effective hCA II inhibitors, with K_I ranging from 18.2 to 133.3 nM (AAZ and SLC-0111: K_I, 12.0 and 960.0 nM, respectively). Compounds 4a–8a effectively inhibited hCA IX, with K_I in the range 8.5–24.9 nM; these values are superior or equivalent to that of AAZ and SLC-0111 (K_I, 25.0 and 45.0 nM, respectively). Compounds 4a–8a displayed effective hCA XII inhibitory activity with K_I values ranging from 8.6 to 43.2 nM (AAZ and SLC-0111: K_I, 5.7 and 4.5 nM, respectively). However, compounds 9b–13b and 14c–18c were found to be micromolar CA inhibitors. For molecular docking studies, compounds 5a, 6a, and 8a were selected.     

Design,synthesis and evaluation of N-substituted saccharin derivatives as selective inhibitors of tumor-associated carbonic anhydrase XII

A series of N-alkylated saccharin derivatives were synthesized and tested for the inhibition of four different isoforms of human carbonic anhydrase (CA, EC 4. 2.1.1): the transmembrane tumor-associated CA IX and XII, and the cytosolic CA I and II. Most of the reported derivatives inhibited CA XII in the nanomolar/low micromolar range, hCA IX with K_Is ranging between 11 and 390 nM, whereas they were inactive against both CA I (K_Is >50 μM) and II (K_Is ranging between 39.1 nM and 50 μM). Since CA I and II are off-targets of antitumor carbonic anhydrase inhibitors (CAIs), the obtained results represent an encouraging achievement for the development of new anticancer candidates without the common side effects of non-selective CAIs. Moreover, the lack of an explicit zinc binding function on these inhibitors opens the way towards the exploration of novel mechanisms of inhibition that could explain the high selectivity of these compounds for the inhibition of the transmembrane, tumor-associated isoforms over the cytosolic ones.     

Design,synthesis & biological evaluation of ferulic acid-based small molecule inhibitors against tumor-associated carbonic anhydrase IX

Carbonic anhydrase IX (CAIX) is an emerging drug target for hypoxia associated cancers. To identify potent and selective inhibitors of CAIX, a small library of ferulic acid (FA) derivatives bearing triazole moiety has been designed, synthesized and evaluated against different human CA isoforms (CAII, CAVA & CAIX). Though most of the compounds showed CAIX inhibition in the micromolar range, compound 7i selectively inhibits CAIX in the nanomolar range (IC₅₀ = 24 nM). In silico analysis revealed binding of 7i with the catalytically important amino acid residues of CAIX. Further, cell-based studies indicate that 7i inhibits the activity of CAIX, decreases the epithelial to mesenchymal transitions, induces apoptosis, inhibits cell migration and colonization potential of cancer cells. Taken together, these results emphasized the use of 7i as a prospective pharmacological lead molecule in CAIX targeted anticancer therapeutics.     

Synthesis,characterization, crystal structure of novel bis-thiomethylcyclohexanone derivatives and their inhibitory properties against some metabolic enzymes

In this study, a series of novel bis-thiomethylcyclohexanone compounds (3a–3j) were synthesized by the addition of thio-Michael to the bis-chalcones under mild reaction conditions. The bis-thiomethylcyclohexanone derivatives (bis-sulfides) were characterized by ¹H NMR, ¹³C NMR, FTIR and elemental analysis techniques. Furthermore, the molecular and crystal structures of 3h, 3i and 3j compounds were determined by single crystal X-ray diffraction studies. In this study, X-ray crystallography provided an alternative and often-complementary means for elucidating functional groups at the enzyme inhibitory site. Acetylcholinesterase (AChE) is a member of the hydrolase protein super family and has a significant role in acetylcholine-mediated neurotransmission. Here, we report the synthesis and determining of novel bis-thiomethylcyclohexanone compounds based hybrid scaffold of AChE inhibitors. The newly synthesized bis-thiomethylcyclohexanone compounds showed K_i values of in range of 39.14–183.23 nM against human carbonic anhydrase I isoenzyme (hCA I), 46.03–194.02 nM against human carbonic anhydrase II isoenzyme (hCA II), 4.55–32.64 nM against AChE and 12.77–37.38 nM against butyrylcholinesterase (BChE). As a result, novel bis-thiomethylcyclohexanone compounds can have promising anti Alzheimer drug potential and record novel hCA I, and hCA II enzymes inhibitor.     

SLC-0111 enaminone analogs, 3/4-(3-aryl-3-oxopropenyl) aminobenzenesulfonamides,as novel selective subnanomolar inhibitors of the tumor-associated carbonic anhydrase isoform IX

SLC-0111, an ureido substituted benzenesulfonamide, is a selective carbonic anhydrase (CA, EC 4.2.1.1) IX inhibitor that is currently in Phase I/II clinical trials for the treatment of advanced hypoxic tumors complicated with metastases. Herein we report the synthesis of two series of 3/4-(3-aryl-3-oxopropenyl) aminobenzenesulfonamides 5a–i and 6a–j as SLC-0111 enaminone congeners. The prepared enaminones were in vitro investigated as inhibitors of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA I, II, IV and IX, using a stopped-flow CO₂ hydrase assay. All these isoforms were inhibited by the enaminones reported here in variable degrees. The target tumor-associated isoform hCA IX was undeniably the most affected one (K_Is: 0.21–7.1 nM), with 6- to 21-fold enhanced activity than SLC-0111 (K_I = 45 nM). All the prepared enaminones displayed interesting selectivity towards hCA IX over hCA I (SI: 32 – >35714), hCA II (SI: 2 – 1689) and hCA IV (SI: 11 – >45454). Of particular interest, bioisosteric replacement of phenyl tail with the bulkier 2-naphthyl tail, sulfonamide 6h, achieved the higher II/IX selectivity herein reported with SI of 1689.     

Discovery of new ureido benzenesulfonamides incorporating 1,3,5-triazine moieties as carbonic anhydrase I,II, IX and XII inhibitors

A series of twenty novel ureido benzenesulfonamides incorporating 1,3,5-triazine moieties substituted on one side with aromatic amines and on the other side with dimethylamine, morpholine and piperidine is reported. The compounds were synthesized from the 4-(3-(4,6-dichloro-1,3,5-triazin-2-yl)ureido)benzensulfonamide (1) by using stepwise nucleophilic substitution of the chlorine atoms of cyanuric chloride. The intermediates 2(a-e) and final compounds 3(a-o) were tested for their efficiency as carbonic anhydrase (CA) inhibitors against four selected physiologically relevant human carbonic anhydrase (CA, EC 4.2.1.1) isoforms, namely, the cytosolic ones hCA I and II, and the transmembrane, tumor associated ones hCA IX, and XII. The compounds 2a, 2e and 3m showed the highest activity for hCA IX with K_is in the range of 11.8–14.6?nM. Most of the compounds showed high hCA IX selectivity over the abundant off-target isoforms hCA I and II. Since hCA IX is a validated drug target for anticancer/antimetastatic agents, these isoform-selective and potent inhibitors may be considered of interest for further medicinal/pharmacologic studies.     

(3,4-Dihydroxyphenyl)(2,3,4-trihydroxyphenyl)methanone and its derivatives as carbonic anhydrase isoenzymes inhibitors

In this study, we have synthesised (3,4-dihydroxyphenyl)(2,3,4-trihydroxyphenyl)methanone and a series of its derivatives (5, 13–16) and tested the ability of these compounds to inhibit two metalloenzyme human carbonic anhydrase (hCA, EC 4.2.1.1) isozymes, hCA I and hCA II. The synthesised compounds showed inhibitory effect on hCA I and hCA II isozymes. The results showed that synthesised compounds (5, 13–16) demonstrated the best inhibition activity against hCA I (IC₅₀: 3.22–54.28 μM) and hCA II (IC₅₀: 18.52–142.01 μM). The compound 14 showed the highest inhibiton effect against hCA I (IC₅₀: 3.22 μM; K_i: 1.19?±?1.4 μM). On the other hand, the compound 13 showed the highest inhibiton effect against hCA II (IC₅₀: 18.52 μM; K_i: 3.25?±?1.13 μM).     

Issue information

Benzothiazepine compounds have a wide range of applications such as antibacterial, antidepressants, anticonvulsants, antihypertensives, antibiotics, antifungal, hypnotic, enzyme inhibitors, antitumor, anticancer and anti‐HIV agents. In this study, the synthesis of novel tetralone‐based benzothiazepine derivatives ( 1–16 ) and their in vitro antibacterial activity and human carbonic anhydrase isoenzymes I and II (hCA I and II) inhibitory effects were investigated. Both isoenzymes were purified by sepharose‐4B‐l ‐tyrosine‐sulfanilamide affinity chromatography from fresh human red blood cells. All compounds demonstrated the low nanomolar inhibitory effects on both isoenzymes using esterase activity. Benzothiazepine derivative 2 demonstrated the best hCA I inhibitory effect with K_i value of 18.19 nM. Also, benzothiazepine derivative 7 showed the best hCA II inhibitory effect with K_i value of 11.31 nM. On the other hand, acetazolamide clinically used as CA inhibitor, showed K_i value of 19.92 nM against hCA I and 33.60 nM against hCA II, respectively.