Carbonic Anhydrase Inhibitors. Schiff Bases of some Aromatic Sulfonamides and Their Metal Complexes: Towards More Selective Inhibitors of Carbonic Anhydrase Isozyme IV

Abstract

Reaction of three aromatic sulfonamides possessing a primary amino group, i.e., sulfanilamide, homosulfanilamide and p-aminoethyl-benzenesulfonamide with heterocyclic and aromatic aldehydes afforded a series of Schiff bases. Metal complexes of some of these Schiff bases with divalent transition ions such as Zn(II), Cu(II), Co(II) and Ni(II) have also been obtained. The new compounds were assayed as inhibitors of three isozymes of carbonic anhydrase (CA). Several of the new compounds showed a modest selectivity for the membrane-bound (bovine) isozyme CA IV (bCA IV) as compared to the cytosolic human isozymes hCA I and II, in contrast to classical inhibitors which generally possess a 17-33 times lower affinity for bCA IV. This greater selectivity toward bCA IV is due mainly to a slightly decreased potency against hCA II relative to classical inhibitors. However, metal complexes of these Schiff bases possessed an increased affinity for hCA II, being less inhibitory against bCA IV. The first type of compounds reported here (i.e., the Schiff bases of aromatic sulfonamides with heterocyclic aldehydes) might thus lead to the development of low molecular weight isozyme specific CA IV inhibitors. The difference in affinity for the three isozymes of the inhibitors reported by us here is tentatively explained on the basis of recent X-ray crystallographic studies of these isozymes and their adducts with substratesiinhibitors     

Carbonic Anhydrase Inhibitors: Schiff's Bases of Aromatic and Heterocyclic Sulfonamides and their Metal Complexes

Schiff's bases were obtained from aromatic/heterocyclic sulfonamides and amino-sulfonamide derivatives, such as sulfanilamide, homosulfanilamide, 4-aminoethyl-benzenesulfonamide and 5-amino-1,3,4-thiadiazole-2-sulfonamide. Metal complexes of some of these Schiff's bases, incorporating Zn(II), Co(II), Ni(II) and Cu(II) ions, were also prepared and tested as inhibitors of the zinc enzyme carbonic anhydrase (CA), and more specifically the red blood cell isozymes I and II. The Schiff's bases behaved as medium potency CA I and CA II inhibitors, whereas their metal complexes showed a highly enhanced potency, with several low nanomolar CA II inhibitors detected.     

Carbonic Anhydrase Inhibitors: Novel Compounds Containing S-NH Moieties: Sulfenamido-Sulfonamides,Sulfenimido-Sulfonamides and their Interaction with Isozymes I,II and IV

Abstract

Reaction of 2-nitrophenyl-and 4-nitrophenylsulfenyl chlorides with aromatic/heterocyclic sulfonamides/bis-sulfonamides containing a free amino, hydrazino or imino group afforded sulfenamido-sulfonamides, or sulfenimido-sulfonamides. Oxidation of these derivatives with potassium permanganate in acetone led to the corresponding bis-sulfonamides. The obtained compounds were assayed as inhibitors of the zinc enzyme carbonic anhydrase (CA), isozymes hCAI, hCAII (human cytosolic forms from red cells) and bCAIV (bovine membrane-associated form). Good inhibition of the three CA isozymes was observed with some of the new compounds, the bis-sulfonamides being more active than the sulfenamido-sulfonamides. Structure-active correlations for the new series of inhibitors are discussed. Some of the sulfenamido-sulfonamides (but not the corresponding bis-sulfonamides) showed topical intraocular pressure lowering effects when applied as a 2% solution directly into the rabbit eye.     

Carbonic Anhydrase Inhibitors. Inhibition of Cytosolic Isozymes I and II and Transmembrane,Cancer-associated Isozyme IX with Anions

Except for sulfonamides, metal complexing anions represent the second class of inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). The first inhibition study of the transmembrane, tumor-associated isozyme CA IX with anions is reported here. Inhibition data of the cytosolic isozymes CA I and CA II with a large number of anionic species such as halides, pseudohalides, bicarbonate, nitrate, hydrosulfide, arsenate, etc., are also provided for comparison. Isozyme IX has an inhibition profile by anions different in some aspects from those of CA I and CA II, that may have interesting physiological consequences.     

Carbonic Anhydrase Inhibitors. Inhibition of Cytosolic Isozymes I and II and Transmembrane,Cancer-associated Isozyme IX with Lipophilic Sulfonamides

A series of new compounds was obtained by reaction of aromatic/heterocyclic sulfonamides incorporating amino groups with N,N-diphenylcarbamoyl chloride and diphenylacetyl chloride. These sulfonamides were assayed for the inhibition of three carbonic anhydrase (CA, EC 4.2.1.1) isozymes: the cytosolic CA I and CA II, and the transmembrane, cancer-associated isozyme CA IX. Good inhibitors against all these isoforms were detected, and the inhibition profile of the newly investigated isozyme IX was observed to be different from that of the cytosolic isozymes, I and II. This may lead to the development of novel anticancer therapies based on the selective inhibition of CA IX.     

Carbonic Anhydrase Inhibitors. Arylsulfonylureido-and Arylureido-Substituted Aromatic and Heterocyclic Sulfonamides: Towards Selective Inhibitors of Carbonic Anhydrase Isozyme I

Abstract

Reaction of twenty aromatic/heterocyclic sulfonamides containing a free amino, imino, hydra-zino or hydroxyl group, with tosyl isocyanate or 3,4-dichlorophenyl isocyanate afforded two series of derivatives containing arylsulfonylureido or diarylureido moieties in their molecule respectively. The new derivatives were assayed as inhibitors of three carbonic anhydrase (CA) isozymes, CA I, II (cytosolic forms) and IV (membrane-bound form). Potent inhibition was observed against all three isozymes but especially against CA I, which is generally 10-75 times less susceptible to inhibition by the classical sulfonamides in clinical use as compared to the other major red cell isozyme, CA II, or the membrane-bound one, CA IV. The derivatives obtained from tosyl isocyanate were generally more potent than the corresponding ones obtained from 3,4-dichlorophenyl isocyanate. This is the first reported example of selective inhibition of CA I and might lead to more selective drugs/diagnostic agents from this class of pharmacologically relevant compounds.     

Carbonic Anhydrase Inhibitors: Inhibition of Isozymes I,II and IV by Sulfamide and Sulfamic Acid Derivatives

Abstract

Sulfamide and sulfamic acid are the simplest compounds containing the SO₂NH₂ moiety, responsible for binding to the Zn(II) ion within carbonic anhydrase (CA, EC 4.2.1.1) active site, and thus acting as inhibitors of the many CA isozymes presently known. Here we describe two novel classes of CA inhibitors obtained by derivatizations of the lead molecules mentioned above. The new compounds, possessing the general formula RSO₂NH-SO₂X (X = OH, NH₂), were obtained by reaction of sulfamide or sulfamic acid with alkyl/arylsulfonyl halides or aryl-sulfonyl isocyanates. A smaller series of derivatives has been obtained by reaction of aromatic aldehydes with sulfamide, leading to Schiff bases of the type ArCH=NSO₂NH₂. All the new compounds act as strong inhibitors of isozymes I, II and IV of carbonic anhydrase. Their mechanism of CA inhibition is also discussed based on electronic spectroscopic measurements on adducts with the Co(II)-substituted enzyme. These experiments led to the conclusion that the new inhibitors are directly coordinated (in a monodentate manner) to the metal ion within the enzyme active site, similarly to the classical inhibitors, the aromatic/heterocyclic sulfonamides.     

Carbonic Anhydrase Inhibitors: Synthesis of Water Soluble Sulfonamides Incorporating a 4-sulfamoylphenylmethylthiourea Scaffold,with Potent Intraocular Pressure Lowering Properties

Reaction of thiophosgene with 4-aminomethyl-benzenesulfonamide afforded 4-isothiocyanatomethyl-benzenesulfonamide, which by reaction with amines, amino acids and oligopeptides, lead to a series of new sulfonamides incorporating a 4-sulfamoylphenyl-methylthiourea scaffold. These new thioureas showed strong affinities towards isozymes I, II and IV of carbonic anhydrase (CA, EC 4.2.1.1). In vitro inhibitory potency was good (in the low nanomolar range) for the derivatives of: amino-benzoic acids, β -phenyl-serine, α -phenyl-glycine, for those incorporating hydroxy- and mercapto-amino acids (Ser, Thr, Cys and Met), hydrophobic amino acids (Val, Leu, Ile), aromatic amino acids (Phe, His, Trp, Tyr; DOPA); dicarboxylic amino acids as well as di-/tri-/tetrapeptides among others. Such CA inhibitors displayed very good water solubility (in the range of 2-3%) as sodium (carboxylate) salts, with pH values for the solutions obtained of 6.5-7.0. Furthermore, in normotensive rabbits, some of them showed an effective and prolonged intraocular pressure (IOP) lowering when administered topically, as 2% solutions.     

Carbonic Anhydrase Activators: Synthesis of High Affinity Isozymes I,II and IV Activators,Derivatives of 4-(Arylsulfonylureido-Amino Acyl)Ethyl-1H-Imidazole

Abstract

Based on the X-ray crystallographic structure of the adduct of human carbonic anhydrase II (hCA II) with the weak activator histamine (Briganti, F., Mangani, S., Orioli, P., Scozzafava, A., Vernaglione, G. and Supuran, C.T. (1997) Biochemistry, 36, 10 384–10 392), a novel class of tight-binding CA activators was designed by using histamine (Hst) as lead molecule. Thus, N-1-tritylsulfenyl Hst was synthesized by reaction of Hst with tetrabromophthalic anhydride followed by protection of its imidazole moiety with tritylsulfenyl chloride. After hydrazinolysis, it afforded a key intermediate which was derivatized at the aliphatic amino group. Reaction of the key intermediate with 4-fluorophenylsulfonylureido amino acids (fpu-AA) or 2-toluenesul-fonylureido amino acids (ots-AA) in the presence of carbodiimides, afforded after deprotection, a series of compounds with the general formula fpu/ots-AA-Hst (fpu = 4-FC₆H₄SO₂NHCO; ots = 2-MeC₆H₄SO₂NHCO). Some structurally related dipeptides with the general formula fpu/ ots-AA1-AA2-Hst (AA, AA1 and AA2 represent amino acyl moieties), were also prepared, by a strategy similar to that used for the simple amino acyl compounds above. The new derivatives proved to be efficient in vitro activators of three CA isozymes. Best activity was shown against hCA I and bCA IV, for which some of the new compounds (such as the Lys, Arg. His or the dipeptide derivatives) showed affinities in the 2–12 nm range (h = human; b = bovine isozymes). hCA II was on the other hand somehow less prone to activation by the new derivatives, which possessed affinities around 30–60 nM for this isozyme. Ex vivo experiments showed some of the new activators to strongly enhance red cell CA activity (180–230%) after incubation with human erythrocytes. This new class of CA activators might lead to the development of drugs/ diagnostic tools for the CA deficiency syndrome, a genetic disease of bone, brain and kidneys.     

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.     

Antibacterial Co(II), Cu(II), Ni(II) and Zn(II) Complexes of Thiadiazole Derived Furanyl,Thiophenyl and Pyrrolyl Schiff Bases

2-Amino-1,3,4-thiadiazole undergoes a condensation reaction with furane-, thiophene- and pyrrole-2-carboxaldehyde to form tridentate NNO, NNS and NNN donor Schiff bases. These Schiff bases were further used to obtain complexes of the type [M(L) 2] X, where M=Co(II), Cu(II), Ni(II) or Zn(II), L=L 1, L 2 or L 3 and X=Cl 2. The new compounds described here have been characterized by their physical, spectral and analytical data, and have been screened for antibacterial activity against several bacterial strains such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The antibacterial potency of the Schiff bases increased upon chelation/complexation in comparison to the uncomplexed Schiff bases against the tested bacterial species thus, opening new approaches to find new ways in the fight against antibiotic-resistant strains.     

Carbonic Anhydrase Inhibitors. Metal Complexes of 5-(2-Chlorophenyl)-1, 3, 4-Thiadiazole-2-Sulfonamide with Topical Intraocular Pressure Lowering Properties: The Influence of Metal Ions Upon the Pharmacological Activity

Metal complexes of a sulfonamide possessing strong carbonic anhydrase (CA) inhibitory properties, 5-(2-chlorophenyl)-1, 3, 4-thiadiazole-2-sulfonamide (chlorazolamide) have been obtained from the sodium salt of the sulfonamide and the following metal ions: Mg(II), Zn(II), Mn(II), Cu(II), Co(II), Ni(II), Be(II), Cd(II), Pb(II), AI(III), Fe(III) and La(III). The original sulfonamide and its complexes were assayed for the in vitro inhibition of three CA isozymes, CA I, II, and IV, some of which play a critical role in ocular fluid secretion. All these compounds (the sulfonamide and its metal complexes) behaved as powerful inhibitors against the three investigated isozymes. The parent sulfonamide possessed an extremely weak topical pressure lowering effect when administered as a 1-2% suspension into the rabbit eye, but some of its metal complexes, such as the Mg(II), Zn(II), Mn(II) and Cu(II) derivatives, lower intraocular pressure (IOP) in experimental animals very well. Ex vivo data showed a 99.5-99.9% CA II inhibition in ocular fluids and tissues of rabbits treated with these agents, proving that the observed IOP lowering is due to CA inhibition. The influence of the different metal ions upon the efficiency of the obtained complexes as pressure lowering drugs are discussed, leading to the possibility of designing more selective; potent pharmacological agents from this class     

Carbonic Anhydrase Inhibitors: Allylsulfonamide,Styrene Sulfonamide,N -allyl Sulfonamides and Some of Their Si,Ge, and B Derivatives

Unsubstituted aromatic, heterocyclic and perfluoroalkylic sulfonamides possessing the general formula RSO 2 NH 2 act as powerful inhibitors of the zinc enzyme carbonic anhydrase (CA). Unsaturated primary/substituted sulfonamides have never been investigated for their interaction with the enzyme. Here it is shown that such compounds, and more precisely allyl-sulfonamide and trans -styrene sulfonamide possessing the above general formula (with R=CH 2 =CH-CH 2 - and C 6 H 5 -CH=CH-, respectively) behave as nanomolar inhibitors of the physiologically relevant isozymes CA I and CA II. Some other derivatives of these two leads (incorporating Si(IV), Ge(IV) and B(III) moieties among others) were also synthesized and investigated for their interaction with CA, but showed decreased affinity for both isozymes. The structure-activity relationship for this class of CA inhibitors is discussed. Furthermore, it was observed that allylsulfonyl chloride is a strong CA inactivator, probably by reacting with amino acid residues critical for the catalytic cycle.     

Carbonic anhydrase inhibitors: metal complexes of a sulfanilamide derived Schiff base and their interaction with isozymes I,II and IV

Metal complexes of aromatic/heterocyclic sulfonamides act as stronger inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1) as compared to the uncomplexed sulfonamides from which they are derived. Here we report the synthesis and inhibition studies against the physiologically relevant isozymes CA I, CA II and CA IV, of a series of metal complexes (Co(II), Ni(II) and Cu(II) derivatives) of a Schiff-base ligand, obtained from sulfanilamide and salicylaldehyde. The best activity was observed for the Cu(II) and Co(II) complexes, against CA II and CA IV, for which inhibition constants in the range of 15-39 and 72-108nM, respectively, were seen. The enhanced efficacy in inhibiting the enzyme may be due to a dual mechanism of action of the metal complexes, which interact with CA both by means of the sulfonamide moieties as well as the metal ions present in their molecule.     

Carbonic Anhydrase Activators: Synthesis of High Affinity Isozymes I,II and IV Activators,Derivatives of 4-(4-Tosylureido-Amino Acyl)Ethyl-1H-Imidazole (Histamine Derivatives)

Reaction of histamine (Hst) with tetrabromophthalic anhydride and protection of its imidazole moiety with tritylsulfenyl chloride, followed by hydrazinolysis, afforded N-1-tritylsulfenyl histamine, a key intermediate which was further derivatized at its aminoethyl moiety. Reaction of the key intermediate with 4-tosylureido amino acids/dipeptides (ts-AA) in the presence of car-bodiimides, afforded after deprotection of the imidazole moiety, a series of compounds with the general formula ts-AA-Hst (ts = 4-MeC₆H₄SO₂NHCO). Some structurally related dipeptide derivatives with the general formula ts-AA l-AA2-Hst, were also prepared, by in a similar way to the amino acyl compounds mentioned above. The new derivatives were examined as activators of three carbonic anhydrase (CA) isozymes, hCA I, hCA II (cytosolic forms) and bCA IV (membrane-bound form). Efficient activation was observed against all three isozymes, but especially against hCA I and bCA IV, with affinities in the 1-10 nanomolar range for the best compounds. hCA II was on the other hand activatable with affinities around 20-50 nM. This new class of CA activators might lead to the development of drugs/diagnostic agents for the CA deficiency syndrome, a genetic disease of bone, brain and kidneys.     

Carbonic anhydrase I,II, IV and IX inhibition with a series of 7-amino-3,4-dihydroquinolin-2(1H)-one derivatives

A series of new derivatives was prepared by derivatisation of the 7-amino moiety present in 7-amino-3,4-dihydroquinolin-2(1H)-one, a compound investigated earlier as CAI. The derivatisation was achieved by: i) reaction with arylsulfonyl isocyanates/aryl isocyanates; (ii) reaction with fluorescein isothiocyanate; (iii) condensation with substituted benzoic acids in the presence of carbodiimides; (iv) reaction with 2,4,6-trimethyl-pyrylium tetrafluoroborate; (v) reaction with methylsulfonyl chloride and (vi) reaction with maleic anhydride. The new compounds were assayed as inhibitors of four carbonic anhydrases (CA, EC 4.2.1.1) human (h) isoforms of pharmacologic relevance, the cytosolic hCA I and II, the membrane-anchored hCA IV and the transmembrane, tumour-associated hCA IX. hCA IX was the most inhibited isoform (K_Is ranging between 243.6 and 2785.6?nm) whereas hCA IV was not inhibited by these compounds. Most derivatives were weak hCA I and II inhibitors, with few of them showing K_Is?相似文献   

Discovery of thiazolin-4-one-based aromatic sulfamates as a new class of carbonic anhydrase isoforms I,II, IV,and IX inhibitors

Herein we report the synthesis of a new series of aromatic sulfamates investigated for the inhibition of four human (h) isoforms of zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), hCA I, II, IV, and IX. The reported derivatives, obtained by a sulfamoylation reaction of the corresponding phenolic precursors, bear arylthiazolin-4-one moieties as spacers between the benzenesulfamate fragment which binds the zinc ion from the active site, and the tail of the inhibitor. Thiazolin-4-ones are biologically privileged scaffolds, endowed with versatile biological activity, such as an anti-proliferative action. Phenolic precursors, also evaluated for CA inhibition, did not exhibit noteworthy efficacy in inhibiting the screened hCAs, whereas low nanomolar inhibitors were evidenced within the sulfamates subset mainly against hCA II (K_Is in the range of 28.7–84.3 nM) and IX (K_Is in the range of 17.6–73.3 nM). The variety of substituents appended at the outer aromatic portion almost generally reduced the inhibitory efficacy against isoforms II and IV, increasing instead that against the tumor-associated isoform IX.     

Synthesis of novel 5-amino-1,3,4-thiadiazole-2-sulfonamide containing acridine sulfonamide/carboxamide compounds and investigation of their inhibition effects on human carbonic anhydrase I,II, IV and VII

Herein, we report that acridine intermediates 5 were obtained from the reduction of nitro acridine derivatives 4, which were synthesized via condensation of dimedone, p-nitrobenzaldehyde with 4-amino-N-(5-sulfamoyl-1,3,4-thiadiazol-2-yl)benzamide, respectively. Then acridine sulfonamide/carboxamide (7a–i) compounds were synthesized by reaction of amino acridine 5 with sulfonyl chlorides and carbamoyl chlorides. The new compounds were characterized by melting points, FT-IR, ¹H NMR, ¹³C NMR and HRMS analyzes. The evaluation of in vitro test of the synthesized compounds against hCA I, II, IV and VII showed that some of them are potent inhibitors. Among them, compound 7e showed the most potent activity against hCA II with a K_I of 7.9 nM.     

Carbonic anhydrase activators: amino acyl/dipeptidyl histamine derivatives bind with high affinity to isozymes I, II and IV and act as efficient activators

Reaction of histamine (Hst) with tetrabromophthalic anhydride and protection of its imidazole moiety with tritylsulfenyl chloride, followed by hydrazinolysis, afforded N-1-tritylsulfenyl-histamine, a key intermediate which was further derivatized at its aminoethyl moiety. Reaction of the key intermediate with N-Boc-amino acids/dipeptides (Boc-AA) in the presence of carbodiimides afforded, after deprotection of the imidazolic and amino moieties, a series of compounds with the general formula AA-Hst (AA=amino acyl; dipeptidyl). The new derivatives were assayed as activators of three carbonic anhydrase (CA) isozymes, hCA I, hCA II (cytosolic forms) and bCA IV (membrane-bound form). Efficient activation was observed against all three isozymes, but especially against hCA I and bCA IV, with affinities in the nanomolar range for the best compounds. hCA II was, on the other hand, activatable with affinities around 10–20 nM. This new class of CA activators might lead to the development of drugs/diagnostic agents for the CA deficiency syndrome, a genetic disease of bone, brain and kidneys.