Kalyan K. Sethi

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 (Kis in the range of 295-10,000 nM), but were more effective hCA II inhibitors (Kis of 1.7-887 nM). The tumor-associated hCA IX was also inhibited, with Kis in the micromolar range, whereas against hCA XII the inhibition constants were in the range of 90-3,746 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.

Carbonic anhydrase inhibitors: Synthesis and inhibition of the human carbonic anhydrase isoforms I, II, VII, IX and XII with benzene sulfonamides incorporating 4,5,6,7-tetrabromophthalimide moiety

A series of 4,5,6,7-tetrabromo-1,3-dioxoisoindolin-2-yl benzenesulfonamide derivatives (compounds 1-8) was synthesized by reaction of benzene sulfonamide derivatives with 4,5,6,7-tetrabromophthalic anhydride moiety. 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, II and VII and the transmembrane tumor-associated isoform hCA IX and XII. The new compounds were good hCA I inhibitors (Kis in the range of 143 to >10,000nM), but were moderately effective, as hCA II inhibitors (Kis of 47-190nM) and poor hCA VII inhibitors (Kis in the range of 54-175nM) compared to acetazolamide. The tumor-associated hCA IX was effectively inhibited with Kis ranging between 8.5 and 234nM and hCA XII with inhibition constants in the range of 6.1-197nM with high selectivity ratio. 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 study of compounds was performed to rationalize the SAR reported over here.

Carbonic anhydrase inhibitors: Synthesis and inhibition of the cytosolic mammalian carbonic anhydrase isoforms I, II and VII with benzene sulfonamides incorporating 4,5,6,7-tetrachlorophthalimide moiety

A series of 4,5,6,7-tetrachloro-1,3-dioxoisoindolin-2-yl benzenesulfonamide derivatives (compounds 1-8) was synthesized by reaction of benzene sulfonamides incorporating primary amino moieties with 4,5,6,7-tetrachlorophthalic anhydride. These sulfonamides were assayed as inhibitors of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). Some of these compounds showed very good in vitro human carbonic anhydrase (hCA) isoforms I, II and VII inhibitory properties, with affinities in the low nanomolar range. Inhibition activities against hCA I were in the range of 159-444nM; against hCA II in the range of 2.4-4515nM, and against hCA VII in the range of 1.3-469nM. The structure-activity relationship (SAR) with this series of sulfonamides is straightforward, with the main features leading to good activity for each isoform being established.

A systematic quantitative approach to rational drug design and discovery of novel human carbonic anhydrase IX inhibitors

Abstract Drug design involves the design of small molecules that are complementary in shape and charge to the biomolecular target with which they interact and therefore will bind to it. Three-dimensional quantitative structure–activity relationship (3D-QSAR) studies were performed for a series of carbonic anhydrase IX inhibitors using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) techniques with the help of SYBYL 7.1 software. The large set of 36 different aromatic/heterocyclic sulfamates carbonic anhydrase (CA, EC 4.2.1.1) inhibitors, such as hCA IX, was chosen for this study. The conventional ligand-based 3D-QSAR studies were performed based on the low energy conformations employing database alignment rule. The ligand-based model gave q2 values 0.802 and 0.829 and r2 values 1.000 and 0.994 for CoMFA and CoMSIA, respectively, and the predictive ability of the model was validated. The predicted r2 values are 0.999 and 0.502 for CoMFA and CoMSIA, respectively. SEA (steric, electrostatic, hydrogen bond acceptor) of CoMSIA has the significant contribution for the model development. The docking of inhibitors into hCA IX active site using Glide XP (Schrödinger) software revealed the vital interactions and binding conformation of the inhibitors. The CoMFA and CoMSIA field contour maps are well in agreement with the structural characteristics of the binding pocket of hCA IX active site, which suggests that the information rendered by 3D-QSAR models and the docking interactions can provide guidelines for the development of improved hCA IX inhibitors as leads for various types of metastatic cancers including those of cervical, renal, breast and head and neck origin.

Carbonic anhydrase I and II inhibition with natural products: caffeine and piperine.

Novel chemotypes with carbonic anhydrase (CA; EC 4.2.1.1) inhibitory action, in addition to the sulphonamide and sulphamate were discovered, many of which are based on natural products. Caffeine and piperine were extracted and tested for inhibition of the human (h) cytosolic isoforms hCA I and II. The IC50 values of caffeine against hCA I was of 55 mM, whereas that of piperine of 60 mM. The IC50 values of caffeine and piperine against hCA II were of 2 mM. Although these are quite weak inhibitors they may constitute leads for developing tighter binding compounds.

A Rational Approach towards the Development of Human Carbonic Anhydrase Inhibitors as Antiepileptic Agent

Antiepileptic activity study considering the MES model and molecular docking studies were performed for a series of previously synthesized dioxoisoindolin benzene sulfonamide derivatives. The reported molecules were investigated as inhibitors of the zinc metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1), specifically against the hCA I and II isoforms. To get a better insight of these molecules as potential inhibitors we specifically consider the hCA I (Ki values in the range 159 nM to >10000 nM) and hCAII (Ki values in range 1.7 nM to >10000 nM). The most potential molecule explored in the study was 3-(4,5,6,7-tetrachloro-1,3-dioxoisoindolin-2-yl)benzenesulfonamide (Ki=27.7 nM), 3-chloro-4-(4,5,6,7-tetrachloro-1,3-dioxoisoindolin-2-yl)benzenesulfonamide(Ki=4.9 nM) and 4-((4-nitro-1,3-dioxoisoindolin-2-yl)methyl)benzenesulfonamide (Ki=34 nM) respectively with obtained p-value <0.01 in the MES study and showed higher antepileptic activity than acetazolamide (AZM). Moreover a well defined docking score with RMSD value of 1.8 throws light on their effective binding to the active site of both 1AZM and 1ZFQ respectively.