[Show abstract][Hide abstract] ABSTRACT: In this investigation, we describe a new approach to chiral synthesis of chloroquine and its analogues. All tested compounds displayed potent activity against chloroquine sensitive as well as chloroquine resistant strains of Plasmodium falciparum in vitro and Plasmodium yoelii in vivo. Compounds S-13b, S-13c, S-13d and S-13i displayed excellent in vitro antimalarial activity with an IC50 value of 56.82, 60.41, 21.82 and 7.94nM, respectively, in the case of resistant strain. Furthermore, compounds S-13a, S-13c and S-13d showed in vivo suppression of 100% parasitaemia on day 4 in the mouse model against Plasmodium yoelii when administered orally. These results underscore the application of synthetic methodology and need for further lead optimization.
[Show abstract][Hide abstract] ABSTRACT: Inhibition of DPP-IV enzyme has taken centre stage as a validated drug target for type 2 diabetes therapy and as a result of research efforts done towards developing effective DPP-IV inhibitors, the first clinical candidate of this class came in focus in 1998. Thus, from 1998 to 2013, these 16-years have witnessed heightened research activities in the discovery and development of clinically relevant inhibitors of DPP-IV as antidiabetic agents. The effective DPP-IV inhibitors have played a key role in this endeavour and as result there are eight approved gliptins in the clinical usage while others are in different stages of clinical trials. A wide variety of DPP-IV inhibitors were synthesized and evaluated; and were classified into several categories based on their core structural features. In this article, classification of all the clinically relevant DPP-IV inhibitors based on selectivity, clinical efficacy and safety profiles are reviewed in terms of generations. This review also encompasses clinical phase wise discussion, developmental progress, chemistry and binding modes of all clinical DPP-IV inhibitors. In addition, major challenges facing the future design and development of safe clinical DPP-IV inhibitor are also briefly mentioned.
Current Medicinal Chemistry 09/2014; · 3.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Novel piperazine-derived conformationally constrained compounds were designed, synthesized, and evaluated for in vitro Dipeptidyl peptidase-IV (DPP-IV) inhibitory activities. From a library of compounds synthesized, 1-(2-(4-(7-Chloro-4-quinolyl)piperazin-1-yl)acetyl)pyrrolidine (2g) was identified as a potential DPP-IV inhibitor exhibiting better inhibitory activity than P32/98, reference inhibitor. The in vivo studies carried out in STZ and db/db mice models indicated that the compound 2g showed moderate antihyperglycemic activity as compared to the marketed drug Sitagliptin. A two-week repeated dose study in db/db mice revealed that compound 2g significantly declined blood glucose levels with no evidence of hypoglycemia risk. Furthermore, it showed improvement in insulin resistance reversal and antidyslipidemic properties. Molecular docking studies established good binding affinity of compound 2g at the DPP-IV active site and are in favor of the observed biological data. These data collectively suggest that compound 2g is a good lead molecule for further optimization studies.This article is protected by copyright. All rights reserved.
Chemical Biology & Drug Design 09/2014; · 2.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Emergence and spread of multidrug resistant strains of Plasmodium falciparum has severely limited the antimalarial chemotherapeutic options. In order to overcome the obstacle, a set of new side-chain modified 4-aminoquinolines were synthesized and screened against chloroquine-sensitive (3D7) and chloroquine-resistant (K1) strains of P. falciparum. The key feature of the designed molecules is the use of methylpiperazine linked α, β(3)- and γ-amino acids to generate novel side chain modified 4-aminoquinoline analogues. Among the evaluated compounds, 20c and 30 were found more potent than CQ against K1 and displayed a four-fold and a three-fold higher activity respectively, with a good selectivity index (SI=5846 and 11,350). All synthesized compounds had resistance index between 1.06 and >14.13 as against 47.2 for chloroquine. Biophysical studies suggested that this series of compounds act on heme polymerization target.
[Show abstract][Hide abstract] ABSTRACT: Gliptins, commonly known as clinical DPP-IV inhibitors have become a new class of potential drug candidate and are being hoped as a permanent eraser for type 2 diabetes. Therefore, gliptins have been a centre of research and development. As a result of the efforts made towards developing effective gliptins, the first clinical proof of concept for efficacy was confirmed in 1998 when NVP-DPP728 came into focus. Thus, from 1998 to 2014, these 17-years of the heightened research towards drug discovery has resulted in seventeen gliptins. Among these, eight gliptins are currently approved and in clinical usages for type 2 diabetes therapies, while others are in different stages of clinical trials. This review covers the various approaches and methodologies used in the syntheses of only those DPP-IV inhibitors in clinical uses having suffix gliptin. In addition, it also encompasses their biological activity and their binding interactions in the active site of DPP-IV that are responsible for their drug candidacy.
[Show abstract][Hide abstract] ABSTRACT: Immuno-modulators in combination with antileishmanial drug miltefosine is a better therapeutic approach for treatment of Visceral Leishmaniasis (VL) as it not only reduces the dose of miltefosine but also shortens the treatment regimen. However, immunological mechanisms behind the perceived benefits of this combination therapy have not been investigated in detail. In the present study, we hypothesized that potential use of drugs that target the host in addition to the parasite might represent an alternative strategy for combination therapy. We investigated immune responses generated in Leishmania donovani infected animals (hamsters and mice) treated with combination of CpG-ODN-2006 and miltefosine at short dose regimen. Infected animals were administered CpG-ODN-2006 (0.4 mg/kg, single dose), as free and liposomal form, either alone or in combination with miltefosine for 5 consecutive days and parasite clearance was evaluated at day 4 and 7 post treatment. Animals that received liposomal CpG-ODN-2006 (lipo-CpG-ODN-2006) and sub-curative miltefosine (5 mg/kg) showed the best inhibition of parasite multiplication (∼97%) which was associated with a biased Th1 immune response in. Moreover, compared to all the other treated groups, we observed increased mRNA expression levels of pro-inflammatory cytokines (IFN-γ, TNF-α and IL-12) and significantly suppressed levels of Th2 cytokines (IL-10 and TGF-β) on day 4 post treatment in animals that underwent combination therapy with lipo-CpG-ODN-2006 and sub-curative miltefosine. Additionally, same therapy also induced heightened iNOS mRNA levels and NO generation, increased IgG2 antibody level and strong T-cell response in these hamsters compared with all the other treated groups. Collectively, our results suggest that combination of lipo-CpG-ODN-2006 and sub-curative miltefosine generates protective T-cell response in an animal model of visceral leishmaniasis which is characterized by strong Th1 biased immune response thereby underlining our hypothesis that combination therapy, at short dose regimen can be used as a novel way of treating visceral leishmaniasis.
PLoS ONE 04/2014; 9(4):e94596. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A number of thiazolidin-4-one and thiazinan-4-one derivatives were prepared by three component condensation in one pot reaction method. These compounds were evaluated for anti-hyperglycemic activity by in vitro and in vivo assay systems. The compounds with thiazolidin-4-one and thiazinan-4-one moieties exhibited significant anti-hyperglycemic activity. A few compounds (3a, 3b, 4a and 4b) have exhibited both anti-hyperglycemic and anti-dyslipidemic activities. Among them the thiazinan-4-one derivative 4a showed maximal (45%) improvement in oral glucose tolerance test in db/db mice at 30 mg/kg oral dose.
European Journal of Medicinal Chemistry 02/2013; 63C:611-620. · 3.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Immunostimulatory peptides potentiate the immune system of the host and are being used as a viable adjunct to established therapeutic modalities in treatment of cancer and microbial infections. Several peptides derived from milk protein have been reported to induce immunostimulatory activity. Human β -casein fragment (54-59), natural sequence peptide (NS) carrying the Val-Glu-Pro-Ile-Pro-Tyr amino acid residues, was reported to activate the macrophages and impart potent immunostimulatory activity. In present study, we found that this peptide increases the clearance of M. bovis BCG from THP-1 cell line in vitro. The key biomolecules, involved in the clearance of BCG from macrophage like, nitric oxide, pro-inflammatory cytokines and chemokines, were not found to be significantly altered after peptide treatment in comparison to the untreated control. Using proteomic approach we found that BTF3a, an isoform of the Basic Transcription Factor, BTF3, was down regulated in THP-1 cell line after peptide treatment. This was reconfirmed by real time RT-PCR and western blotting. We report the BTF3a as a novel target of this hexapeptide. Based on the earlier findings and the results from the present studies, we suggest that the down regulation of BTF3a following the peptide treatment may augment the M. bovis BCG mediated apoptosis resulting in enhanced clearance of M. bovis BCG from THP-1 cell line.
PLoS ONE 09/2012; 7(9):e45905. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new series of quinoline analogs have been synthesized and found active against P. falciparum in vitro and P. yoelli in vivo. Compounds 8, 10 and 11 exhibited superior in vitro activity compared to chloroquine. Selected compounds 8, 10 and 11 exhibited significant suppression of parasitaemia in vivo assay. These analogs form a complex with hematin and inhibit the β-hematin formation, suggesting that this class of compounds act on a heme polymerization target. Further this study confirms that quinoline ring nitrogen is essential for both transportation of the molecule across the membrane as well as for tight binding to hematin.
Journal of Enzyme Inhibition and Medicinal Chemistry 09/2012; 28(5). · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present study describes the synthesis of a series of new 4-aminoquinoline-derived thiazolidines and evaluation of their antimalarial activity against a NF-54 strain of Plasmodium falciparum in vitro and N-67 strain of Plasmodium yoelii in vivo. Among the series, two compounds, 2-(4-chloro-phenyl)-thiazolidine-4-carboxylic acid [2-(7-chloro-quinolin-4-ylamino)-ethyl]-amide hydrochloride (14) and 2-(2,6-dichloro-phenyl)-thiazolidine-4-carboxylic acid [2-(7-chloro-quinolin-4-ylamino)-ethyl]-amide hydrochloride (22) exhibited significant suppression of parasitaemia in the in vivo assay. All the analogues were found to form strong complex with haematin and inhibited the β-haematin formation in vitro. These results suggest that these compounds act on heme polymerization target.
Journal of Enzyme Inhibition and Medicinal Chemistry 03/2012; · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Development of efficient and safe nucleic acid carriers (vectors) is one of the essential requirements for the success of gene therapy. Here, we have evaluated the gene transfer capability of chitosan-PEI (CP) conjugates prepared by conjugating low molecular weight branched polyethylenimine (LMWP) with depolymerized chitosans (7 and 10 kDa) via their terminal aldehyde/keto groups. The CP conjugates interacted efficiently with nucleic acids and also showed higher cellular uptake. These conjugates on complexation with DNA yielded nanoparticles in the size range of 100-130 nm (in case of C7P) and 115-160 nm (in case of C10P), which exhibited significantly higher transfection efficiency (~2-42 folds) in vitro compared to chitosans (high and low mol. wt.) and the commercially available transfection reagents retaining cell viability almost comparable to the native chitosan. Of the two CP conjugates, chitosan 7 kDa-LMWP (C7P) displayed higher gene transfer ability in the presence and absence of serum. Luciferase reporter gene analysis in male Balb/c mice receiving intravenous administration of C7P3/DNA polyplex showed the maximum expression in their spleen. Further, tuftsin, a known macrophage targeting molecule, was tethered to C7P3 and the resulting complex, i.e., C7P3-T/DNA, exhibited significantly higher gene expression in cultured mouse peritoneal macrophages as compared to unmodified C7P3/DNA complex without any cytotoxicity demonstrating the suitability of the conjugate for targeted applications. Conclusively, the study demonstrates the potential of the projected conjugates for gene delivery for wider biomedical applications.
[Show abstract][Hide abstract] ABSTRACT: Current drugs for the treatment of visceral leishmaniasis are inadequate, and their efficacies are also compromised due to suppression of immune function during the course of infection. Miltefosine is the only promising orally active antileishmanial drug, but due to its long half-life, there is risk of development of resistance. To overcome these problems, efforts are needed to develop combination therapy of miltefosine with effective immunostimulating agents where a decrease of parasitic burden and simultaneous enhancement of adaptive immunity can be achieved. In the present study, we have explored the antileishmanial efficacy of a subcurative dose of miltefosine in combination with free as well as liposomal palmitoyl tuftsin (p-tuftsin) using a Leishmania donovani/BALB/c mouse model. When miltefosine (2.5 mg/kg for 5 days) was given with free p-tuftsin, the inhibitory effect was significantly increased from 49.6% to 66% (P < 0.01), which was further enhanced up to 81% (P < 0.001) when given after liposomal encapsulation of p-tuftsin. Significant enhancement in parasitic inhibition (93%, P < 0.01) was witnessed when animals were co-administered with liposomal p-tuftsin + 5 mg/kg × 5 days dose of miltefosine (72.1%). Enhancement in the production of Th1 cytokines (IL-12, TNF-α, and IFN-γ), reactive oxygen, and nitrogen metabolites was witnessed in the combination group. A remarkable increase in phagocytosis index was also observed indicating overall immunological enhancement to antileishmanial activity of miltefosine by p-tuftsin.
Parasitology Research 03/2012; 111(2):563-70. · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It is widely appreciated that the vascular endothelium is capable of modulating vascular smooth muscle tone suiting it well for its role as an important regulator of a number of diverse biological processes. Endothelial dysfunction is an early manifestation of atherothrombosis and a consequence of the established disease. Although several arginine derivatives alkylated at one of the guanidino nitrogen were found to inhibit vasorelaxation induced by acetylcholine, activity of the corresponding arginine esters is not reported. The present work was therefore designed to synthesize and evaluate series of novel arginine derivatives to obtain further insight into structure-activity relationship in this series of compounds. Present study involves assessment of activity of these novel compounds on the vascular tone of rat thoracic aorta in comparison with l-arginine analog, that is, l-nitro-arginine methyl ester (l-NAME). Results from the present study showed that full reversal of phenylephrine-mediated contraction was achieved by cumulative applications of acetylcholine (3nm-300μm), which were abolished when the aortic rings were pretreated with l-NAME (300μm). Results from the present study demonstrated that these novel arginine derivatives cause significant yet reversible reduction in acetylcholine-mediated relaxation, similar to that of L-NAME.
Chemical Biology & Drug Design 12/2011; 79(4):459-69. · 2.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In view of the severe immunosuppression in visceral leishmaniasis (VL), a rational approach to effectively combat the parasitic scourge would be to enhance the immune status of the host. Use of CpG oligodeoxynucleotide (CpG-ODN) against leishmaniasis has previously been reported, especially as an immunomodulator and adjuvant with various immunogens. In the present study, experiments were carried out with BALB/c mice and hamsters infected with Leishmania donovani. Immunostimulating class B bacterial CpG-ODN namely, ODN-2006, was administered at various doses by the intraperitoneal (i.p.) route. The dose of CpG-ODN-2006 (1 nM/single dose) showing the most antileishmanial activity was given as free and liposomal forms with different doses of miltefosine, namely, 5 and 10 mg/kg of body weight, for 5 days in mice and hamsters, respectively. Among the various groups, mice coadministered liposomal CpG-ODN and miltefosine (5 mg/kg) showed the best inhibitory effect (97% parasite inhibition) compared with free CpG-ODN plus miltefosine and miltefosine, free CpG-ODN, and liposomal CpG-ODN given separately. Similar responses were observed in the case of hamsters, where the combination of liposomal CpG-ODN with miltefosine (10 mg/kg) gave 96% parasite inhibition. Promising antileishmanial efficacy was observed in animals treated with liposomal CpG-ODN and miltefosine.
Antimicrobial Agents and Chemotherapy 07/2011; 55(7):3461-4. · 4.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
[Show abstract][Hide abstract] ABSTRACT: A new series of 4-aminoquinoline derivatives have been synthesized and found to be active against both susceptible and resistant strains of Plasmodium falciparum in vitro. Compound 1-[3-(7-chloro-quinolin-4-ylamino)-propyl]-3-cyclopropyl-thiourea (7) exhibited superior in vitro activity against resistant strains of P. falciparum as compared to chloroquine (CQ). All the compounds showed resistance factor between 0.59 and 4.31 as against 5.05 for CQ. Spectroscopic studies suggested that this class of compounds act on heme polymerization target.
European Journal of Medicinal Chemistry 11/2010; 45(11):4990-6. · 3.43 Impact Factor