Saurabh Manaswita Verma

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.

Evidence for bactericidal activities of lipidic nanoemulsions against Pseudomonas aeruginosa

Pseudomonas aeruginosa has been implicated in a broad range of infections and shown to acquire rapid resistance to anti-microbial agents. In the present, study we have used particular amalgamation of specific lipids that hold innate antibacterial activities, which can be transformed into cationized and non-cationized nanoemulsions. The anti-Pseudomonas activities were then elucidated by transmission/scanning electron microscopy, and atomic force microscopy. The microscopic studies revealed the cell lysis due to the formation of blebs, exudation of essential cellular contents and loss of characteristics contour of the cells. The microscopic studies were then corroborated by zone of inhibition, cytoplasmic release studies, time dependent killing and MIC determination. Conclusively, it can be inferred that the delivery issues of antibiotics could be reassessed by using certain excipients that possess inherent antibacterial properties. This will not only avoid unnecessary introduction of inactive excipients in the body, but will also reduce the dose of antibiotics because of synergistic effects of excipients and drug acting together.

Antibacterial activity of cationised and non-cationised placebo lipidic nanoemulsion using transmission electron microscopy

The primary aim of the study was to observe the morphological changes taking place on Escherichia coli when treated with non-cationised placebo lipidic emulsion (NCPLE) and cationised placebo lipidic emulsion (CPLE). The particle size of NCPLE and CPLE indicated the mean diameter of 10.77 ± 0.20 nm and 56.98 ± 1.718 nm, respectively. The zeta potential of NCPLE and CPLE depicted the potential of −10.8 ± 0.80 mV and +20.9 ± 3.25 mV, respectively. Agar diffusion study indicated higher inhibition zone of 21.4 ± 0.85 mm for CPLE as evaluated against 14.7 ± 0.76 mm for NCPLE. Transmission electron micrographs of Escherichia coli treated with NCPLE and CPLE showed the potential of blank nanoemulsions as antibacterial, which can be used as a therapeutic agent. The bacterial cell being negatively charged attracts the cationised nanoemulsions from the bulk of dispersion. As the concentration of nanoemulsion increased in the vicinity of the bacterial cell, the degree of collisions increased between the cationised nanoemulsion leading to coalescence and the formation of a pool of emulsion containing bacterial cells leading to cell death. The study demonstrated that placebo lipidic nanoemulsion (NCPLE & CPLE) may itself be used as an active therapeutic agent for the treatment of bacterial infections. Moreover, it can also be used as a carrier system for antibacterial drugs for the two-pronged synergistic effect.

Consequences of lipidic nanoemulsions on membrane integrity and ultrastructural morphology of Staphylococcus aureus

The present study divulges the consequences of lipidic nanoemulsions (cationized and non-cationized) on morphology and membrane integrity of Staphylococcus aureus using transmission electron microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Transmission electron microscopic (TEM) images reveal that the cationized lipidic emulsions (CLEs) remained adhered even after the hostile treatment to remove nanoemulsions by centrifugation owing to electrostatic attraction between CLE and negatively charged bacterial surface. TEM images portray the extensive cell lyses owing to the release of cytoplasmic content when treated with both CLE and Non-CLE (NCLE). The AFM analysis of the NCLE and CLE treated S. aureus cells showed the root mean square roughness of 11.3 ± 2.8 nm and 17.7 ± 3.2 nm, respectively. The complete losses of bacterial colonies after 45 min of contact with NCLE were observed. No viable bacterial colonies were noticeable after 10 min of contact when treated with CLE, indicating better rate of killing with respect to NCLE. Similar results were obtained in the zone of inhibition studies. Significant (p < 0.05) increase of cytoplasmic material was observed both in NCLE (0.192 ± 0.003) and CLE (0.308 ± 0.012) as compared to control (0.019 ± 0.002). The present finding illustrates that the NCLE and CLE had caused significant membrane disorganization leading to release of cytoplasmic content causing irreversible cell damage, which is in accordance with the TEM, SEM and AFM studies.

3D-QSAR study of 8-azabicyclo[3.2.1] octane analogs antagonists of cholinergic receptor.

3D-QSAR models of Comparative of Molecular Field Analysis (CoMFA) and Comparative of Molecular Similarities Indices Analysis (CoMSIA) of 20 8-azabicyclo[3.2.1] octane (potent muscarinic receptor blocker) was performed. These benztropine analogs were optimized using ligand based alignment method. The conventional ligand-based 3D-QSAR studies were performed based on the low energy conformations employing database alignment rule. The ligand-based model gave q(2) value 0.819 and 0.810 and r(2) value 0.991 and 0.988 for CoMFA and CoMSIA, respectively, and the predictive ability of the model was validated. Results indicate that the CoMFA and CoMSIA models could be reliable model which may be used in the design of novel muscarinic antagonists as leads.

Antibacterial action of lipidic nanoemulsions using atomic force microscopy and scanning electron microscopy on Escherichia coli

The present study demonstrates the mechanism of bactericidal effect rendered by cationic and non-cationic lipidic emulsions using atomic force microscopy (AFM) and scanning electron microscopy. The AFM images of treated Escherichia coli cells indicated the conformational alteration from rod-shaped bacteria to a fluid-flattened structure with the presence of pore in the centre of bacterium, indicating the cell lysis. Root mean square roughness increased substantially due to exposure of underlying rugose peptidoglycan layer when treated with non-cationized lipidic nanoemulsions (NCLE). The cationised-lipidic-emulsion (CLE) treated E. coli cells frequently showed division septa along the length of E. coli which was not visible in non-cationised treated bacterial cells. The enhanced adhesion between CLE and negatively charged bacteria leads to lesser time required to kill the bacteria as compared to NCLE.

Design and synthesis of chroman derivatives with dual anti-breast cancer and antiepileptic activities

A series of chroman derivatives was designed, prepared, and examined for their anti-breast cancer and antiepileptic activities. All synthesized compounds yielded results that were in good agreement with spectral data. The bioassay showed that some of the resultant compounds exerted remarkable inhibitory effects on growth of human breast cancer cell line MCF-7. In particular, compound 6i (the concentration required for 50% inhibition of cell growth [GI50] =34.7 µM) exerted promising anticancer activity toward MCF-7 cell line. Additionally, compounds 6b, 6c, 6d, 6e, 6g, 6i, and 6l showed advanced antiepileptic activity than reference drugs. None of the compounds showed neurotoxicity, as determined by the rotarod test. The obtained results proved that these distinctive compounds could be relevant as models for future discovery and research, as well as for the production of more number of active derivatives.

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.