Novel bisbenzimidazoles with antileishmanial effectiveness

Compounds with potentialities as novel chemotherapeutic agents in leishmaniasis at preclinical level

Leishmaniasis are neglected infectious diseases caused by kinetoplastid protozoan parasites from the genus Leishmania. These sicknesses are present mainly in tropical regions and almost 1 million new cases are reported each year. The absence of vaccines, as well as the high cost, toxicity or resistance to the current drugs determines the necessity of new treatments against these pathologies. In this review, several compounds with potentialities as new antileishmanial drugs are presented. The discussion is restricted to the preclinical level and molecules are organized according to their chemical nature, source and molecular targets. In this manner, we present antimicrobial peptides, flavonoids, withanolides, 8-aminoquinolines, compounds from Leish-Box, pyrazolopyrimidines, and inhibitors of tubulin polymerization/depolymerization, topoisomerase IB, proteases, pteridine reductase, N-myristoyltransferase, as well as enzymes involved in polyamine metabolism, response against oxidative stress, signaling pathways, and sterol biosynthesis. This work is a contribution to the general knowledge of these compounds as antileishmanial agents.

Synthesis, in vitro biological assessment, and molecular docking study of benzimidazole-based thiadiazole derivatives as dual inhibitors of α-amylase and α-glucosidase

The clinical significance of benzimidazole-containing drugs has increased in the current study, making them more effective scaffolds. These moieties have attracted strong research interest due to their diverse biological features. To examine their various biological significances, several research synthetic methodologies have recently been established for the synthesis of benzimidazole analogs. The present study aimed to efficiently and quickly synthesize a new series of benzimidazole analogs. Numerous spectroscopic techniques, including ¹H-NMR, ¹³C-NMR, and HREI-MS, were used to confirm the synthesized compounds. To explore the inhibitory activity of the analogs against α-amylase and α-glucosidase, all derivatives (1-17) were assessed for their biological potential. Compared to the reference drug acarbose (IC₅₀ = 8.24 ± 0.08 µM), almost all the derivatives showed promising activity. Among the tested series, analog 2 (IC₅₀ = 1.10 ± 0.10 & 2.10 ± 0.10 µM, respectively) displayed better inhibitory activity. Following a thorough examination of the various substitution effects on the inhibitory capacity of α-amylase and α-glucosidase, the structure-activity relationship (SAR) was determined. We looked at the potential mechanism of how active substances interact with the catalytic cavity of the targeted enzymes in response to the experimental results of the anti-glucosidase and anti-amylase. Molecular docking provided us with information on the interactions that the active substances had with the various amino acid residues of the targeted enzymes for this purpose.

Dimeric Drugs

This review intends to summarize the structures of an extensive number of symmetrical-dimeric drugs, having two monomers linked via a bridging entity while emphasizing the large versatility of biologically active substances reported to possess dimeric structures. The largest number of classes of these compounds consist of anticancer agents, antibiotics/antimicrobials, and anti-AIDS drugs. Other symmetrical-dimeric drugs include antidiabetics, antidepressants, analgesics, anti-inflammatories, drugs for the treatment of Alzheimer's disease, anticholesterolemics, estrogenics, antioxidants, enzyme inhibitors, anti-Parkisonians, laxatives, antiallergy compounds, cannabinoids, etc. Most of the articles reviewed do not compare the activity/potency of the dimers to that of their corresponding monomers. Only in limited cases, various suggestions have been made to justify unexpected higher activity of the dimers vs. the corresponding monomers. These suggestions include statistical effects, the presence of dimeric receptors, binding of a dimer to two receptors simultaneously, and others. It is virtually impossible to predict which dimers will be preferable to their respective monomers, or which linking bridges will lead to the most active compounds. It is expected that the extensive number of articles summarized, and the large variety of substances mentioned, which display various biological activities, should be of interest to many academic and industrial medicinal chemists.

Structure-Based Design of Dimeric Bisbenzimidazole Inhibitors to an Emergent Trimethoprim-Resistant Type II Dihydrofolate Reductase Guides the Design of Monomeric Analogues

The worldwide use of the broad-spectrum antimicrobial trimethoprim (TMP) has induced the rise of TMP-resistant microorganisms. In addition to resistance-causing mutations of the microbial chromosomal dihydrofolate reductase (Dfr), the evolutionarily and structurally unrelated type II Dfrs (DfrBs) have been identified in TMP-resistant microorganisms. DfrBs are intrinsically TMP-resistant and allow bacterial proliferation when the microbial chromosomal Dfr is TMP-inhibited, making these enzymes important targets for inhibitor development. Furthermore, DfrBs occur in multiresistance plasmids, potentially accelerating their dissemination. We previously reported symmetrical bisbenzimidazoles that are the first selective inhibitors of the only well-characterized DfrB, DfrB1. Here, their diversification provides a new series of inhibitors (K _i = 1.7-12.0 μM). Our results reveal two prominent features: terminal carboxylates and inhibitor length allow the establishment of essential interactions with DfrB1. Two crystal structures demonstrate the simultaneous binding of two inhibitor molecules in the symmetrical active site. Observations of those dimeric inhibitors inspired the design of monomeric analogues, binding in a single copy yet offering similar inhibition potency (K _i = 1.1 and 7.4 μM). Inhibition of a second member of the DfrB family, DfrB4, suggests the generality of these inhibitors. These results provide key insights into inhibition of the highly TMP-resistant DfrBs, opening avenues to downstream development of antibiotics for combatting this emergent source of resistance.

An overview of recent advances in duplex DNA recognition by small molecules

As the carrier of genetic information, the DNA double helix interacts with many natural ligands during the cell cycle, and is amenable to such intervention in diseases such as cancer biogenesis. Proteins bind DNA in a site-specific manner, not only distinguishing between the geometry of the major and minor grooves, but also by making close contacts with individual bases within the local helix architecture. Over the last four decades, much research has been reported on the development of small non-natural ligands as therapeutics to either block, or in some cases, mimic a DNA–protein interaction of interest. This review presents the latest findings in the pursuit of novel synthetic DNA binders. This article provides recent coverage of major strategies (such as groove recognition, intercalation and cross-linking) adopted in the duplex DNA recognition by small molecules, with an emphasis on major works of the past few years.

Diversity oriented synthesis of benzimidazole-based biheterocyclic molecules by combinatorial approach: a critical review

Because of the wide ranging bioactivities associated with the benzimidazole nucleus, this review highlights the advances made in the synthesis of benzimidazole-based biheterocyclic molecules by combinatorial approaches.

Antileishmanial drug discovery: comprehensive review of the last 10 years

This review covers the current aspects of leishmaniasis including marketed drugs, new antileishmanial agents, and possible drug targets of antileishmanial agents.

Metal-catalyzed uncaging of DNA-binding agents in living cells†Electronic supplementary information (ESI) available: Synthesis and characterization of the studied molecules and required precursors. NMR, UV, and fluorescence spectra, titrations, control experiments, and detailed procedures for cell uptake and co-staining experiments. See DOI: 10.1039/c3sc53317dClick here for additional data file

Ruthenium-catalyzed activation of DNA-binding compounds in aqueous buffers and in cellular environments.

Attachment of alloc protecting groups to the amidine units of fluorogenic DNA-binding bisbenzamidines or to the amino groups of ethidium bromide leads to a significant reduction of their DNA affinity. More importantly, the active DNA-binding species can be readily regenerated by treatment with ruthenium catalysts in aqueous conditions, even in cell cultures. The catalytic chemical uncaging can be easily monitored by fluorescence microscopy, because the protected products display both different emission properties and cell distribution to the parent compounds.

The therapeutic journey of benzimidazoles: a review

Presence of benzimidazole nucleus in numerous categories of therapeutic agents such as antimicrobials, antivirals, antiparasites, anticancer, anti-inflammatory, antioxidants, proton pump inhibitors, antihypertensives, anticoagulants, immunomodulators, hormone modulators, CNS stimulants as well as depressants, lipid level modulators, antidiabetics, etc. has made it an indispensable anchor for development of new therapeutic agents. Varied substitutents around the benzimidazole nucleus have provided a wide spectrum of biological activities. Importance of this nucleus in some activities like, Angiotensin I (AT(1)) receptor antagonism and proton-pump inhibition is reviewed separately in literature. Even some very short reviews on biological importance of this nucleus are also known in literature. However, owing to fast development of new drugs possessing benzimidazole nucleus many research reports are generated in short span of time. So, there is a need to couple the latest information with the earlier information to understand the current status of benzimidazole nucleus in medicinal chemistry research. In the present review, various derivatives of benzimidazole with different pharmacological activities are described on the basis of substitution pattern around the nucleus with an aim to help medicinal chemists for developing an SAR on benzimidazole derived compounds for each activity. This discussion will further help in the development of novel benzimidazole compounds.

From multiply active natural product to candidate drug? Antibacterial (and other) minor groove binders for DNA

Natural products that bind to DNA in the minor groove are valuable templates for drug design. Examples include distamycin, netropsin, duocarmycin and anthramycin. Anticancer and anti-infective drugs feature strongly amongst their derivatives. The structures and activities of chemotypes with various therapeutic actions are discussed in the context of the broader field of therapeutically active minor groove binders. The evolution of a series of exceptionally potent and nontoxic antibacterial compounds is discussed using the general design principle of introducing additional hydrophobicity into the distamycin template to increase the strength of binding to DNA. As well as potent antibacterial compounds, antifungal and antiparasitic compounds with exceptional cellular activity against trypanosomes have been identified. Possible mechanisms of action including gene regulation and topoisomerase inhibition are discussed with the need in mind to understand selective toxicity in the series to support future drug discovery.

Antimalarial and antitubercular nostocarboline and eudistomin derivatives: synthesis, in vitro and in vivo biological evaluation

The synthesis of nine nostocarboline derivatives with substitutions of the 2-methyl group by alkyl, aryl and functionalized residues, 10 symmetrical bis cationic dimers linking 6-Cl-norharmane through the 2-position and fifteen derivatives of the marine alkaloids eudistomin N and O is reported. These compounds were evaluated in vitro against four parasites (Trypanosoma brucei rhodesiense STIB 900, Trypanosoma cruzi Tulahuen C2C4, Leishmania donovani MHOM-ET-67/L82 axenic amastigotes, and Plasmodium falciparum K1 strain), against Mycobacterium tuberculosis H37Rv, Mycobacterium smegmatis mc(2)155 and Corynebacterium glutamicum ATCC13032, and cytotoxicity was determined against L6 rat myoblast cells. Nostocarboline and derivatives displayed potent and selective in vitro inhibition of P. falciparum with weak cytotoxicity. The dimers displayed submicromolar inhibition of L. donovani and T. brucei, and nanomolar activity against P. falciparum, albeit with pronounced cytotoxicity. One dimer showed a MIC(99) value against M. tuberculosis of 2.5 microg/ml. The alkylated eudistomin N and O derivatives displayed activities down to 18 nM against P. falciparum for N-Me Eudistomin N. Four dimers, nostocarboline and three eudostomin derivatives were evaluated in an in vivo Plasmodium berghei mouse model. No significant activity was observed for the dimers, but a 50% reduction in parasitaemia was observed at 4 x 50 mg/kg ip for nostocarboline.

Imidazole-annelated ferrocene derivatives as highly selective and sensitive multichannel chemical probes for Pb(II) cations

New ferrocenyl-containing imidazopyridine and imidazophenazine receptors 2-5 show high selective affinity for Pb(II) ions over a range of other metal ions examined through different channels. Imidazopyridine-ferrocene dyad 2 behaves as a highly selective redox, chromogenic, and fluorescent chemosensor molecule for Pb(2+) cations: the oxidation redox peak is anodically shifted (DeltaE(1/2) = 150 mV), and the low energy band of the absorption spectrum is red-shifted (Deltalambda = 44 nm) upon complexation with this metal cation. This change in the absorption spectrum is accompanied by a color change from colorless to orange, which allows the potential for "naked eye" detection. The emission spectrum undergoes an important chelation-enhanced fluorescence (CHEF) effect (CHEF = 620), with an unprecedented detection limit of 2.7 microg L(-1). The presence of Zn(2+) cations also induced a perturbation of the redox potential, absorption, and emission spectra although in less extension than those found with Pb(2+) cations. Imidazophenazine-ferrocene dyad 3 has also shown its ability for sensing Pb(2+) cations through redox (DeltaE(1/2) = 120 mV), absorption (Deltalambda = 23 nm), and emission (CHEF = 133) channels, whereas the presence of Zn(2+) only has a little effect on the emission spectrum (CHEF = 74). The electrochemical changes observed in the two-armed ferrocenes 4 and 5 upon complexation show that the potential shift is higher for Zn(2+) ions (DeltaE(1/2) = 190-170 mV) than for Pb(2+) ions (DeltaE(1/2) = 180-110 mV), which is in clear contrast to those observed for the monoarmed ferrocenes 2 and 3. The recognition properties of the two-armed imidazopyridine-ferrocene triad 4 are quite similar to those exhibited by the parent monosubstituted receptor 2, and the most salient features are a strong perturbation of the redox wave (DeltaE(1/2) = 180 mV), a dramatic increasing of the fluorescent quantum yield (Phi(complex)/Phi(ligand) = 890) in the presence of Pb(2+), while the optical responses toward Zn(2+) cations were silent. The two-armed imidazophenazine-ferrocene triad 5 senses Pb(2+) cations through perturbation of the oxidation potential of the Fe(II)/Fe(III) redox couple (DeltaE(1/2) = 110 mV), important blue shift (Deltalambda = 160 nm) of the high energy band in the absorption spectrum, and a remarkable increase of the emission band (CHEF = 220), whereas smaller changes were observed in the presence of Zn(2+) cations. (1)H NMR studies as well as DFT calculations have been carried out to get information about which molecular sites are involved in the binding event.

Synthesis and SAR of alkanediamide-linked bisbenzamidines with anti-trypanosomal and anti-pneumocystis activity

A series of alkanediamide-linked bisbenzamidines was synthesized and tested in vitro against a drug-sensitive strain of Trypanosoma brucei brucei, a drug-resistant strain of Trypanosoma brucei rhodesiense and Pneumocystiscarinii. Bisbenzamidines linked with longer alkanediamide chains were potent inhibitors of both strains of T. brucei. However, bisbenzamidines linked with shorter alkanediamide chains were the most potent compounds against P. carinii. N,N'-Bis[4-(aminoiminomethyl)phenyl] hexanediamide, 4 displayed potent inhibition (IC50=2-3 nM) against T. brucei and P. carinii, and was non-cytotoxic in the A549 human lung carcinoma cell line. The inhibitory bioactivity was significantly reduced when the amidine groups in 4 were moved from the para to the meta positions or replaced with amides.

Leishmanicidal activity of aliphatic and aromatic lactones: correlation structure-activity

Several aliphatic and aromatic lactones and two dimers were synthesized using the sequence: allylation - esterification - metathesis. These compounds were active in vitro against intracellular amastigotes of Leishmania panamensis. The structure-activity relationship showed the importance of the aliphatic side chain to enhance the biological activity and to obtain lower cytotoxicity. It was also observed that a decrease in the size of the lactone ring increases the selectivity index.