Barij Nayan Sinha

Towards development of selective and reversible pyrazoline based MAO-inhibitors: Synthesis, biological evaluation and docking studies.

Ten novel 3,5-diaryl pyrazolines were synthesized and investigated for their monoamine oxidase (MAO) inhibitory property. All the molecules were found to be reversible and selective inhibitor for either one of the isoform (MAO-A or MAO-B). Further insights in the theoretical evaluation of the possible interactions between the compounds and monoamine oxidases (MAO-A or MAO-B) have been developed through docking studies. The theoretical values are in congruence with their experimental values.

Small molecules with structural similarities to siderophores as novel antimicrobials against Mycobacterium tuberculosis and Yersinia pestis.

Drugs inhibiting the iron scarcity-induced, siderophore-mediated iron-scavenging systems of Mycobacterium tuberculosis (Mtb) and Yersinia pestis (Yp) may provide new therapeutic lines of defense. Compounds with structural similarities to siderophores were synthesized and evaluated as antimicrobials against Mtb and Yp under iron-limiting conditions, which mimic the iron scarcity these pathogens encounter and must adapt to in the host, and under standard iron-rich conditions for comparison. New antimicrobials were identified, some of which warrant exploration as initial leads against potentially novel targets and small-molecule tools to assist in the elucidation of targets specific to iron-scarcity adapted Mtb and Yp.

Virtual Screening Studies to Design Potent CDK2-Cyclin A Inhibitors

The cell division cycle is controlled by cyclin-dependent kinases (CDK), which consist of a catalytic subunit (CDK1-CDK8) and a regulatory subunit (cyclin A-H). Pharmacophore analysis indicates that the best inhibitor model consists of (1) two hydrogen bond acceptors, (2) one hydrogen bond donor, and (3) one hydrophobic feature. The HypoRefine pharmacophore model gave an enrichment factor of 1.31 and goodness of fit score of 0.76. Docking studies were carried out to explore the structural requirements for the CDK2-cyclin A inhibitors and to construct highly predictive models for the design of new inhibitors. Docking studies demonstrate the important role of hydrogen bond and hydrophobic interactions in determining the inhibitor-receptor binding affinity. The validated pharmacophore model is further used for retrieving the most active hits/lead from a virtual library of molecules. Subsequently, docking studies were performed on the hits, and novel series of potent leads were suggested based on the interaction energy between CDK2-cyclin A and the putative inhibitors.

Pyrazoline-based mycobactin analogues as MAO-inhibitors

3,5-Diaryl carbothioamide pyrazolines designed as mycobactin analogs (mycobacterial siderophore) were reported to be potent antitubercular agents under iron limiting condition in our earlier study. Clinical complications of newly introduced antibiotic Linezolid, due its MAO inhibitory activity, prompted us to evaluate our compounds for their MAO-inhibitory activity against rat liver MAO-A and MAO-B as pyrazolines were reported to be antidepressants and MAO inhibitors. The present study carried out with this pilot library of 32 compounds will provide us with necessary information for designing antitubercular molecules with reduced MAO-inhibitory activity and also help us in identifying a selective MAO-B inhibitor which has potential clinical utility in neurodegenerative disorders. Thirty-two compounds analyzed has shown spectrum of activity from selective to nonselective against two isoforms of rat liver MAO-A and MAO-B and also as competitive, reversible to non-competitive, irreversible. It is also interesting to note that anti-tubercular compound 11, 14 and 16 were also found to be selective inhibitors of rat liver MAO-B. Docking studies with human MAO shows that compound 11 interacts with the catalytic site of both the isoforms, suggesting compound 11 as nonselective inhibitor of human MAO isoforms.

Development of selective and reversible pyrazoline based MAO-A inhibitors: Synthesis, biological evaluation and docking studies.

3,5-Diaryl pyrazolines analogs were synthesized and evaluated for their monoamine oxidase (MAO) inhibitory activity. The compounds were found reversible and selective towards MAO-A with selectivity index in the magnitude of 10(3)-10(5). The docking studies were carried out to gain further structural insights of the binding mode and possible interactions with the active site of MAO-A. Interestingly, the theoretical (K(i)) values obtained by molecular docking studies were in congruence with their experimental (K(i)) values.

Design, synthesis and anticancer activity of piperazine hydroxamates and their histone deacetylase (HDAC) inhibitory activity.

Six compounds were synthesized with piperazine in linker region and hydroxamate as Zinc Binding Group (ZBG). They were screened against three cancer cell-lines (NCIH460; HCT116; U251). Compounds 5c and 5f with GI(50) value of 9.33+/-1.3 microM and 12.03+/-4 microM, respectively, were tested for their inhibitory potential on hHDAC8. Compound 5c had IC(50) of 33.67 microM. Compounds were also screened for their anticancer activity against HL60 human promyelocytic leukemia cell line due to the presence of pharmacophoric features of RR inhibitors in them. Compound 5c had IC(50) of 0.6 microM at 48h.

Monoamine oxidase inhibitory activity of 3,5-biaryl-4,5-dihydro-1H-pyrazole-1-carboxylate derivatives.

Ethyl and phenyl carbamate derivatives of pyrazoline (3a-3h) were synthesized and tested for their MAO inhibitory activity. All the compounds were found to be selective towards MAO-A. Phenyl carbamates (3e-3h) were better than ethyl carbamates (3a-3d) and displayed the best selectivity index. Compound 3f (KiMAO-A; 4.96 ± 0.21 nM) was found to be equally potent as that of standard drug, Moclobemide (KiMAO-A; 5.01 ± 0.13 nM) but with best selectivity index (8.86 × 10(-5)). Molecular docking studies with R &S conformer of 3f revealed S-enantiomer is better than R-enantiomer as reported earlier by other groups. It is proposed that VdWs radii of the substitution (bulkiness) in ring B determine the potency of phenyl carbamates.

Pyrazoline based MAO inhibitors: Synthesis, biological evaluation and SAR studies

Twenty-two pyrazoline derivatives were synthesized and tested for their human MAO (hMAO) inhibitory activity. Twelve molecules with unsubstituted ring A and substituted ring C (5-16) were found to be potent inhibitors of hMAO-A isoform with SI(MAO-A) in the order 10(3) and 10(4). Ten molecules with unsubstituted ring A and without ring C (21-30), in which eight molecules (21, 23-26, and 28-30) were selective for hMAO-A, one for hMAO-B (22) and the other one non-selective (27). Presence of ring C increases potency as well as SI towards hMAO-A; however its absence decreases both potency and SI towards hMAO-A and hMAO-B.

Fragment and knowledge-based design of selective GSK-3β inhibitors using virtual screening models

Glycogen Synthase Kinase 3beta is one of the important targets in the treatment of type II diabetes and Alzheimers disease. Currently this target is in pursuit for type II diabetes and a few GSK-3beta inhibitors have been now advanced to Phases I and II of clinical trials. The best validated HypoGen model consists of four pharmacophore features; 1) two hydrogen bond acceptors, 2) one hydrogen bond donor and 3) one hydrophobic. This pharmacophore model correlates well with the docking model, one hydrogen bond acceptor is necessary for the H-bond interaction with VAL135, and second hydrogen bond acceptor is important for the H-bond interactions with ARG141 and the hydrophobic feature may be required for the weak H-bond interactions with ASP133. The comparative model was developed from analogue and structure-based models like Catalyst, Glide SP & XP, Gold Fitness & ChemScore and Ligand Fit using multiple linear regression analysis. A virtual library of 10,000 molecules was generated employing fragment and knowledge-based approach and the comparative model was used to predict the activities of these molecules. The H-bond with ARG141 appears to be unique to GSK-3beta and explains the high GSK-3beta selectivity observed for 1H-Quinazolin-4-ones and Benzo[e][1,3]oxazin-4-ones. This understanding of protein-ligand interactions and molecular recognition increases the rapid development of potent and selective inhibitors, and also helps to eliminate the increase in number of false positives and negatives.

Monoamine Oxidase Inhibitory Activity of Novel Pyrazoline Analogues: Curcumin Based Design and Synthesis

A series of new 2-methoxy-4-(5-phenyl-4,5-dihydro-1H-pyrazol-3-yl)phenolderivatives, 4-13, were synthesized and tested for their human MAO inhibitory activity. All the compounds were found to be selective and reversible toward hMAO-A except 4, a selective inhibitor of hMAO-B and 12, a nonselective inhibitor. Compound 7 was found to be a potent inhibitor of hMAO-A with Ki = 0.06 ± 0.003 μM and was having selectivity index of (SI = 1.02 × 10(-5)). It was found to be better than standard drug, Moclobemide (hMAO-A with Ki = 0.11 ± 0.01 μM) with selectivity index of SI = 0.049. Molecular docking simulation was carried out to understand the crucial interactions responsible for selectivity and potency.