Arijit Basu

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.

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.

Development of CoMFA and CoMSIA models of cytotoxicity data of anti-HIV-1-phenylamino-1H-imidazole derivatives

3D-QSAR models of 1-Phenylamino-1H-imidazole derivatives with cytotoxic potential have been developed using CoMFA and CoMSIA. Models were built keeping both 10% and 25% of molecules in test set. The Database and Field-Fit alignments were used for CoMFA model development. The best QSAR model was obtained from CoMFA analysis using Database alignment and employing 25% molecules in the test set (r(pred)(2) of 0.91 and r(m)(2) of 0.652). Database alignment with different fields such as Steric (S), Electrostatic (E), Acceptor (A), Donor (D) and Hydrophobic (H) was employed for CoMSIA model development. The best CoMSIA model was obtained by using the SHE fields and employing 25% molecules in the test set (r(pred)(2) of 0.789 and r(m)(2) of 0.410).

Synthesis and Ribonucleotide reductase inhibitory activity of thiosemicarbazones

Ribonucleotide reductase (RR) is an important therapeutic target for anticancer drugs. The structure of human RR features a 1:1 complex of two homodimeric subunits, hRRM1 and hRRM2. Prokaryotically expressed and highly purified recombinant human RR subunits, hRRM1 and hRRM2, were used for holoenzyme-based [(3)H]CDP reduction in vitro assay. Ten new thiosemicarbazones (7-16) were synthesized and screened for their RR inhibitory activity. Two thiosemicarbazones derived from p-hydroxy benzaldehyde (9 and 10) were found to be active but less potent than the standard, Hydroxyurea (HU). Guided by the activity of compounds 9 and 10, 11 new thiosemicarbazones (17-27) derived from p-hydroxy benzaldehyde were prepared and screened for their RR inhibitory activity. All the 11 compounds were more potent than HU.

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.

Synthesis, Antimicrobial and Anticancer Activity of New Thiosemicarbazone Derivatives

Thiosemicarbazones of p‐aminobenzoic acid (PABA) were synthesized and tested for their antimicrobial and anticancer activity. Hydroxamate derivatives 4a–4l were found to have better antimicrobial and anticancer activity than their acid counterpart. Compound 4d was found to have good antimicrobial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Vibrio cholerae, and Bacillus subtilis with IC50 value of about 1 µM. Compound 4f showed potent antifungal activity against Candida albicans (IC50 = 1.29 µM) and compound 4h showed potent anticancer activity (IC50 = 0.07 µM).

Anticonvulsant activity of Benkara malabarica (Linn.) root extract: In vitro and in vivo investigation

AIM OF THE STUDY To systematically investigate the anticonvulsant activity of methanol extract of Benkara malabarica roots and to provide a biochemical basis elucidating its mode of action. METHODS The median lethal dose (LD(50)) of Benkara malabarica extract was determined. The anticonvulsant activity of the extract was assessed in strychnine-induced and isoniazide-induced convulsion models; phenytoin (20mg/kg) and diazepam (1mg/kg) were used as standards, respectively. Percentage protection provided by the drug was accounted as decrease in the number of convulsions within 8h of observation. Mechanism of action was studied by performing GABA transaminase (GABA-T) assay, isolated from rat brain. Active constituent was isolated and characterized from the plant extract. RESULTS The median lethal dose (LD50) of Benkara malabarica was found to be more than 500 mg/kg. It demonstrated 30% and 35% protection against strychnine-induced convulsions and 60% and 80% protection against isoniazide-induced convulsions, at doses of 25mg/kg and 50mg/kg, respectively. Enzyme assay results revealed that Benkara malabarica extract possesses GABA-T inhibitory activity (IC50=0.721 mg/ml). Scopoletin which was identified as the major constituent of the extract was found to be an inhibitor of GABA-T (IC50=10.57 microM). CONCLUSIONS The anticonvulsant activity of the plant extract is predominantly GABA mediated and may be due to the action of scopoletin alone or is a result of synergy of different compounds in the extract in which scopoletin is the major constituent.

Structure based virtual screening of GSK-3β: Importance of protein flexibility and induced fit

GSK-3beta, one of the vital enzymes responsible for various phosphorylation catalysis. Induced fit mechanism and the presence of conserved water molecule(s) in the active site poses complexity during the process of virtual screening. The present investigation reveals the practical strategy to handle the induced fit mechanism of GSK-3beta though flexible docking protocol. This protocol provides an enrichment of 70% in top 1% of the dataset with a rank correlation of >0.9 and found better in comparison to earlier reported protocols.

Exploring Different Virtual Screening Strategies for Acetylcholinesterase Inhibitors

The virtual screening problems associated with acetylcholinesterase (AChE) inhibitors were explored using multiple shape, and structure-based modeling strategies. The employed strategies include molecular docking, similarity search, and pharmacophore modeling. A subset from directory of useful decoys (DUD) related to AChE inhibitors was considered, which consists of 105 known inhibitors and 3732 decoys. Statistical quality of the models was evaluated by enrichment factor (EF) metrics and receiver operating curve (ROC) analysis. The results revealed that electrostatic similarity search protocol using EON (ET_combo) outperformed all other protocols with outstanding enrichment of >95% in top 1% and 2% of the dataset with an AUC of 0.958. Satisfactory performance was also observed for shape-based similarity search protocol using ROCS and PHASE. In contrast, the molecular docking protocol performed poorly with enrichment factors <30% in all cases. The shape- and electrostatic-based similarity search protocol emerged as a plausible solution for virtual screening of AChE inhibitors.