Synergy of clavine alkaloid ‘chanoclavine’ with tetracycline against multi-drug-resistant E. coli

The emergence of multi drug resistance (MDR) in Gram-negative bacteria (GNB) and lack of novel classes of antibacterial agents have raised an immediate need to identify antibacterial agents, which can reverse the phenomenon of MDR. The purpose of present study was to evaluate synergy potential and understanding the drug resistance reversal mechanism of chanoclavine isolated from Ipomoea muricata against the multi-drug-resistant clinical isolate of Escherichia coli (MDREC). Although chanoclavine did not show antibacterial activity of its own, but in combination, it could reduce the minimum inhibitory concentration (MIC) of tetracycline (TET) up to 16-folds. Chanoclavine was found to inhibit the efflux pumps which seem to be ATPase-dependent. In real-time expression analysis, chanoclavine showed down-regulation of different efflux pump genes and decreased the mutation prevention concentration of tetracycline. Further, in silico docking studies revealed significant binding affinity of chanoclavine with different proteins known to be involved in drug resistance. In in silico ADME/toxicity studies, chanoclavine was found safe with good intestinal absorption, aqueous solubility, medium blood–brain barrier (BBB), no CYP 2D6 inhibition, no hepatotoxicity, no skin irritancy, and non-mutagenic indicating towards drug likeliness of this molecule. Based on these observations, it is hypothesized that chanoclavine might be inhibiting the efflux of tetracycline from MDREC and thus enabling the more availability of tetracycline inside the cell for its action.     

Kinetic characterization of a slow-binding inhibitor of Bla2: thiomaltol

The increasing prevalence of drug resistant bacteria is a pandemic problem. Metallo-β-lactamases (MBLs) are one of the main causes of drug resistance due to hydrolysis of β-lactam antibiotics. Thus, the development of effective inhibitors of MBLs remains urgent. The compound thiomaltol was used as a lead compound to investigate its ability to inhibit metallo-β-lactamase from Bacillus anthracis (Bla2), which causes anthrax. Kinetic evaluation with nitrocefin as a substrate indicates that thiomaltol inhibits Bla2 in a time-dependent manner with an IC₅₀ value of 290 µM after 20?min preincubation. Progress curve analysis and reversibility tests suggest that thiomaltol is a reversible, slow-binding inhibitor with a K_i of 85?±?30 µM. Furthermore, studies on the modality of inhibition and in silico analysis indicate thiomaltol to be a competitive inhibitor. The results demonstrate that thiomaltol is a promising lead compound for slow binding inhibitor design of Bla2.     

Design,synthesis and biological evaluation of novel tetrahydroisoquinoline derivatives as P-glycoprotein-mediated multidrug resistance inhibitors

Multidrug resistance (MDR) is one of the main obstacles of clinical chemotherapy. A great deal of research shows that the occurrence of drug resistance in various malignant tumors is closely related to the expression of P-glycoprotein (P-gp) on the surface of the cell membrane. In this paper, based on the structure-activity relationship of phenylethyl tetrahydroisoquinoline, we choose tariquidar as the lead compound for the design and synthesis of 17 novel tetrahydroisoquinoline P-gp inhibitors. Additionally, in vitro and in vivo cytotoxicity assays and reversed MDR activity assays were evaluated. Among them, compound 3 had a good reversal of MDR activity and the reversal mechanism study of it was carried out. All of these results demonstrated that compound 3 was considered to be a promising P-gp-mediated MDR reversal candidate.     

Designed P-glycoprotein inhibitors with triazol-tetrahydroisoquinoline-core increase doxorubicin-induced mortality in multidrug resistant K562/A02 cells

Multidrug resistance (MDR) refers to the cross-resistance of cancer cells to one drug, accompanied by other drugs with different mechanisms and structures, which is one of the main obstacles of clinical chemotherapy. Overexpression of P-glycoprotein (P-gp) was an extensively studied cause of MDR. Therefore, inhibiting P-gp have become an important strategy to reverse MDR. In this study, two series of triazole-tetrahydroisoquinoline-core P-gp inhibitors were designed and synthesized. Among them, compound I-5 had a remarkable reversal activity of MDR activity and the preliminary mechanism study was also carried out. All the results proved that compound I-5 was considered as a promising P-gp-mediated MDR reversal candidate.     

Validation of NAD synthase inhibitors for inhibiting the cell viability of Leishmania donovani: In silico and in vitro approach

Abstract

NAD (nicotinamide adenine dinucleotide) synthase catalyses the biochemical synthesis of NAD, from nicotinic acid adenine dinucleotide (NAAD). NAD may be synthesized through the de novo pathways and/or the salvage pathways in cells. However, in Leishmania parasite, the synthesis of NAD solely depends on the salvage pathways. NAD synthetase is widely explored as a drug target in various microorganisms. In Bacillus anthracis, a group of sulphonamides 5599, 5617 and 5824 and complex amide 5833 were reported to have activity at micromolar range against NAD synthetase. Hence, in the present study, the same group of sulphonamides and complex amide were validated through in silico and in vitro studies for its efficiency towards Leishmania donovani NAD synthase. In silico study revealed the ligands 5824 and 5833 to have better docking score. Molecular dynamics simulation for a duration of 50 ns of all the ligand–protein complexes suggested that the complexes with the ligands 5824 and 5833 were stable and interacting. In vitro and ex vivo studies have shown that 5824 and 5833 inhibit the cell viability of the organism at a lower concentration than 5599 and 5617. Hence, with further in vivo validation, 5824 (or its synthetic analogues) and 5833 could be the choice that may work synergistically with other potential drugs in treating drug-resistant cases of leishmaniasis.

Communicated by Ramaswamy H. Sarma     

Unveiling the Anthelminthic Potential of Merremia vitifolia Stem through in Vitro and in Silico Approach

This study aimed to assess the anthelmintic activity of methanol extracts from Merremia vitifolia stems using a combination approach encompassing experimental, in vitro, and in silico evaluations. Despite the well-recognized pharmacological properties of M. vitifolia, its potential as an anthelmintic agent remained unexplored. This plant's anthelmintic potential was assessed on adult earthworms (Pheretima posthuma), revealing a dose-dependent reduction in spontaneous motility leading to paralysis and eventual mortality. The most effective dose of M. vitifolia (200 mg/ml) for anthelmintic effects on Pheretima posthuma was identified. Complementary in silico investigations were also conducted, employing Autodock PyRx 0.8 for docking studies of reported M. vitifolia compounds. Notably, quercetin emerged as a promising candidate with superior binding energies against β-tubulin (−8.3 Kcal/mol). Moreover, this comprehensive research underlines the anthelmintic potential of Merremia vitifolia stem extract and highlights quercetin as a noteworthy compound for further investigation in the quest for novel anthelmintic agents.     

Detection of tetracycline and macrolide resistance determinants in enterococci of animal and environmental origin using multiplex PCR

An occurrence of resistance to tetracycline (TET) and erythromycin (ERY) was ascertained in 82 isolates of Enterococcus spp. of animal and environmental origin. Using E test, 33 isolates were resistant to TET and three isolates to ERY. Using polymerase chain reaction (PCR; single and multiplex), the TET determinants tet(M) and tet(L) were detected in 35 and 13 isolates, respectively. Twelve isolates carried both tet(M) and tet(L) genes. Eight isolates possessed ermB gene associated with ERY resistance. Multiplex PCR was shown to be a suitable method for simultaneous determination of all three resistance determinants that occurred most frequently in bacteria isolated from poultry. This study also demonstrates that gastrointestinal tract of broilers may be a reservoir of enterococci with acquired resistance to both TET and ERY that can be transferred to humans via food chain.     

Synthesis,Anti-Fungal Potency and In silico Studies of Novel Steroidal 1,4-Dihydropyridines

Working principle of azoles as antifungals is the inhibition of fungal CYP51/lanosterol-14α-demethylase via selective coordination with heme iron. This interaction can also cause side effects by binding to host lanosterol-14α-demethylase. Hence, it is necessary to design, synthesize and test new antifungal agents that have different structures than those of azoles and other antifungal drugs of choice in clinical practice. Consequently, a series of steroidal 1,4-dihydropyridine analogs 16 – 21 were synthesized and screened for their in vitro anti-fungal activity against three Candida species as steroids-based medications have low toxicity, less vulnerability to multi-drug resistance, and high bioavailability by being capable of penetrating the cell wall and binding to specific receptors. Initially, Claisen–Schmidt condensation takes place between steroidal ketone (dehydroepiandrosterone) and an aromatic aldehyde forming steroidal benzylidene 8 – 13 followed by Hantzsch 1,4-dihydropyridine synthesis resulting in steroidal 1,4-dihydropyridine derivatives 16 – 21 . The results exhibited that compound 17 has significant anti-fungal potential with an MIC value of 750 μg/ml for C. albicans and C. glabrata and 800 μg/ml for C. tropicalis. In silico molecular docking and ADMET studies were also performed for compounds 16 – 21 .     

Design and development of novel p-aminobenzoic acid derivatives as potential cholinesterase inhibitors for the treatment of Alzheimer’s disease

Based on the quantitative structure-activity relationship (QSAR), some novel p-aminobenzoic acid derivatives as promising cholinesterase enzyme inhibitors were designed, synthesized, characterized and evaluated to enhance learning and memory. The in vitro enzyme kinetic study of the synthesized compounds revealed the type of inhibition on the respective acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. The in vivo studies of the synthesized compounds exhibited significant reversal of cognitive deficits in the animal models of amnesia as compared to standard drug donepezil. Further, the ex vivo studies in the specific brain regions like the hippocampus, hypothalamus, and prefrontal cortex regions also exhibited AChE inhibition comparable to standard donepezil. The in silico molecular docking and dynamics simulations studies of the most potent compound 22 revealed the consensual interactions at the active site pocket of the AChE.     

Catharanthus roseus: micropropagation and in vitro techniques

Different methods of in vitro culture of Catharanthus roseus provide new sources of plant material for the production of secondary metabolites such as indole alkaloids. Callus, cell suspension, plantlets, and transgenic roots cultured in the bioreactor are used in those experiments. The most promising outcomes include the production of the following indole alkaloids: ajmalicine in unorganised tissue, catharanthine in the leaf and cell culture in the shake flask and airlift bioreactor, and vinblastine in shoots and transformed roots. What is very important, enzymatic coupling of monomeric indole alkaloids, vindoline and catharanthine, is possible to form vinblastine in cell cultures. The method of catharanthine and ajmalicine production in the suspension culture in bioreactors has been successful. In this method, elicitation may be used acting on different metabolic pathways. Also of interest is the method of obtaining arbutin from the callus culture of C. roseus conducted with hydroquinone. The transformed root culture seems to be the most promising for alkaloid production. The genetically transformed roots, obtained by the infection with Agrobacterium rhizogenes, produce higher levels of secondary metabolites than intact plants. Also, whole plants can be regenerated from hairy roots. The content of indole alkaloids in the transformed roots was similar or even higher when compared to the amounts measured in studies of natural roots. The predominant alkaloids in transformed roots are ajmalicine, serpentine, vindoline and catharanthine, found in higher amounts than in untransformed roots. Transformed hairy roots have been also used for encapsulation in calcium alginate to form artificial seeds.     

Discovery of novel [1,2,4]triazolo[4,3-a]quinoxaline aminophenyl derivatives as BET inhibitors for cancer treatment

Bromodomain and extra-terminal (BET) proteins, a class of epigenetic reader domains has emerged as a promising new target class for small molecule drug discovery for the treatment of cancer, inflammatory, and autoimmune diseases. Starting from in silico screening campaign, herein we report the discovery of novel BET inhibitors based on [1,2,4]triazolo[4,3-a]quinoxaline scaffold and their biological evaluation. The hit compound was optimized using the medicinal chemistry approach to the lead compound with excellent inhibitory activities against BRD4 in the binding assay. The substantial antiproliferative activities in human cancer cell lines, promising drug-like properties, and the selectivity for the BET family make the lead compound (13) as a novel BRD4 inhibitor motif for anti-cancer drug discovery.     

Simplified Derivatives of Dibenzylbutyrolactone Lignans from Hydrocotyle bonariensis as Antitrypanosomal Candidates

The search for the pharmacophore of a bioactive compound, crucial for drug discovery studies, involves the adequate arrangement of different atoms in the molecule. As part of a continuous work aiming discovery of new drug candidates against the protozoan parasite Trypanosoma cruzi, the hexane extract of Hydrocotyle bonariensis was subjected to a bioactivity-guided fractionation to afford two chemically related dibenzylbutyrolactone lignans – hinokinin ( 1 ) and hibalactone ( 2 ). Compounds 1 and 2 showed activity against trypomastigote with EC₅₀ values of 17.0 and 69.4 μM, respectively. Compound 1 was also active against the clinically relevant form of the parasite, amastigotes, displaying an EC₅₀ value of 34.4 μM. The structure-activity relationship (SAR) indicated that the absence of the double bond at C-7 is a crucial feature for the increment of the antiparasitic activity. The lethal action of the most potent compound 1 was investigated in the trypomastigotes. The fluorescent-based assay with SYTOX Green demonstrated a significant alteration of the plasma membrane permeability of the parasite. Additionally, compound 1 demonstrated no significant hemolytic activity in mice erythrocytes at 200 μM. To search the pharmacophore, three different simplified compounds – 3,4-methylenedioxydihydrocinnamic acid ( 3 ), 3,4-methylenedioxydihydrocinnamic alcohol ( 4 ) and 3,4-methylenedioxycinnamic acid ( 5 ) – were prepared and tested against T. cruzi. These derivatives displayed EC₅₀ values of 37.2 ( 3 ), 25.8 ( 4 ) and 73.5 ( 5 ) μM against trypomastigotes, and 41.3 ( 3 ) and 48.2 ( 4 ) μM against amastigotes, whereas compound 5 was inactive. Except for compound 2 , which resulted in a CC₅₀ value of 114.5 μM, all compounds showed no mammalian cytotoxicity at 200 μM. An in silico ADMET study was performed and predicted values demonstrated an acceptable drug-likeness profile for compounds 1 – 5 . Despite the minor reduction in the potency, the simplified derivatives retained the antitrypanosomal activity against the intracellular amastigotes, even with 95 % reduction of their molecular weight. Additionally, in silico studies suggested them as more soluble compounds, making these simplified structures promising scaffolds for optimization studies in Chagas disease.     

An Investigation of Molecular Targeting of MMP-9 for Endometriosis Using Algal Bioactive Molecules

Endometriosis is a chronic inflammatory disease that occurs due to the presence of endometrial tissue outside the uterine cavity. It affects from 5% to 10% of women of reproductive age. High levels of matrix metalloproteinase (especially MMP-9) have been observed in women suffering from endometriosis. Thus, the aim of this study was to investigate the naturally anti-inflammatory compounds available from an algal source that can target the MMP-9 by various in silico approaches. The target 1L6J (Crystal structure of human matrix metalloproteinase MMP-9) structure was retrieved from the PDB database. Five compounds such as Eckol, Sargafuran, Vitamin E, Docosahexaenoic acid, Fucoidan and Elagolix were selected based on ‘Lipinski’s rule of five’ using the PubChem database. The pharmacokinetics, ADMET properties and biological activity of these compounds were predicted computationally using databases such as PreADME, SWISS-ADME, pkCSM and PASS. Comparative analysis of the bioactive compounds with the target was performed by AutoDock 4.2.6. Using LigPlot v.2.2, the target residues interacting with the compounds were visualised in a 2D manner. Based on the results, Eckol exhibited the highest binding energy value of −7.82 kcal/mol, whereas the Elagolix (control drug) showed a binding energy of −4.88 kcal. We conclude that Eckol can be a potent inhibitor of target MMP-9 with least side effects when compared to the control drug. Hence, this compound can be effectively explored by further in vitro and in vivo studies to develop more effective treatments for Endometriosis.     

Iron N-(2-hydroxy acetophenone) glycinate (FeNG), a non-toxic glutathione depletor circumvents doxorubicin resistance in Ehrlich ascites carcinoma cells in vivo

Multidrug resistance-associated protein 1 (MRP1) reduces intracellular anticancer drug accumulation either by co transporting them with glutathione (GSH) or extruding drug-GSH conjugates outside of the cell. Thus, MRP1 confers multidrug resistance (MDR) and worsen successful chemotherapeutic treatment against cancer. Although the exact mechanism of MRP1 involved in MDR remains unknown, the elevated level of intracellular GSH is considered as a key factor responsible for MDR in cancer. Hence the quest for non-toxic molecules that are able to deplete intracellular GSH has profound importance to subdue MDR. The present preclinical study depicts the resistance reversal potentiality of an iron complex; viz. Ferrous N-(2-hydroxy acetophenone) glycinate (FeNG) developed by us in doxorubicin resistant Ehrlich ascites carcinoma (EAC/Dox) cells. FeNG potentiate cytotoxic effect of doxorubicin on EAC/Dox cells ex vivo and also increases the survivability EAC/Dox bearing Swiss albino mice in vivo as well. Moreover, in vivo administration of FeNG significantly depletes intracellular GSH with ensuant increase in doxorubicin concentration in EAC/Dox cells without alternation of MRP1 expression. In addition, intra-peritoneal (i.p.) application of FeNG in normal or EAC/Dox bearing mice does not cause any systemic toxicity in preliminary trials in mouse Ehrlich ascites carcinoma model. Therefore, the present report provides evidence that FeNG may be a promising new resistance modifying agent against drug resistant cancers.     

Inhibition of Bacillus anthracis metallo-β-lactamase by compounds with hydroxamic acid functionality

Abstract

Metallo-β-lactamases (MBLs) that catalyze hydrolysis of β-lactam antibiotics are an emerging threat due to their rapid spread. A strain of the bacterium Bacillus anthracis has its ability to produce and secrete a MBL, referred to Bla2. To address this challenge, novel hydroxamic acid-containing compounds such as 3-(heptyloxy)-N-hydroxybenzamide (compound 4) and N-hydroxy-3-((6-(hydroxyamino)-6-oxohexyl)oxy)benzamide (compound 7) were synthesized. Kinetic analysis of microbial inhibition indicated that the both sides of hydroxamic acids containing compound 7 revealed a reversible, competitive inhibition with a K_i value of 0.18?±?0.06?μM. The result has reflected that the both sides of dihydroxamic acids in a molecule play a crucial role in the binding affinity rather than monohydroxamic containing compound 4 which was unable to inhibit Bla2. In addition, in silico analysis suggested that compound 7 was coordinated with a zinc ion in the active site of enzyme. These observations suggest that the dihydroxamic acid-containing compound may be a promising drug candidate, and a further implication for designing new inhibitors of Bla2.     

Bioinformatics approaches for new drug discovery: a review

Prolonged antibiotic therapy for the bacterial infections has resulted in high levels of antibiotic resistance. Initially, bacteria are susceptible to the antibiotics, but can gradually develop resistance. Treating such drug-resistant bacteria remains difficult or even impossible. Hence, there is a need to develop effective drugs against bacterial pathogens. The drug discovery process is time-consuming, expensive and laborious. The traditionally available drug discovery process initiates with the identification of target as well as the most promising drug molecule, followed by the optimization of this, in-vitro, in-vivo and in pre-clinical studies to decide whether the compound has the potential to be developed as a drug molecule. Drug discovery, drug development and commercialization are complicated processes. To overcome some of these problems, there are many computational tools available for new drug discovery, which could be cost effective and less time-consuming. In-silico approaches can reduce the number of potential compounds from hundreds of thousands to the tens of thousands which could be studied for drug discovery and this results in savings of time, money and human resources. Our review is on the various computational methods employed in new drug discovery processes.     

Phenotypic and genotypic bacterial antimicrobial resistance in liquid pig manure is variously associated with contents of tetracyclines and sulfonamides

Aims: Antibiotic residues as well as antibiotic‐resistant bacteria in environmental samples might pose a risk to human health. This study aimed to investigate the association between antibiotic residues and bacterial antimicrobial resistance in liquid pig manure used as fertilizer. Methods and Results: Concentrations of tetracyclines (TETs) and sulfonamides (SULs) were determined by liquid chromatography‐mass spectrometry in 305 pig manure samples; antibiotic contents were correlated to the phenotypic resistance of Escherichia coli (n = 613) and enterococci (n = 564) towards up to 24 antibiotics. In 121 samples, the concentration of the TET resistance genes tet(M), tet(O) and tet(B) was quantified by real‐time‐PCR. TETs were found in 54% of the samples. The median sum concentration of all investigated TETs in the positive samples was 0·73 mg kg^?1. SULs were found with a similar frequency (51%) and a median sum concentration of 0·15 mg kg^?1 in the positive samples. Associated with the detection of TETs and/or SULs, resistance rates were significantly elevated for several substances – some of them not used in farm animals, e.g. chloramphenicol and synercid. In addition, multiresistant isolates were found more often in samples containing antibiotics. Analysis of the resistance genes tet(M) and tet(O) already showed a significant increase in their concentrations – but not in tet(B) – in the lowest range of total TET concentration. Mean tet(M) concentrations increased by the factor of 4·5 in the TET concentration range of 0·1–1 mg kg^?1, compared to negative manure samples. Conclusions: Antibiotic contamination of manure seems to be associated with a variety of changes in bacterial resistance, calling for a prudent use of antibiotics in farm animals. Significance and Impact of the Study: This study provides an interdisciplinary approach to assess antimicrobial resistance by combining the microbiological analysis of bacterial resistance with high quality chemical analysis of antibiotic residues in a representative number of environmental samples.     

Design,Synthesis and Molecular Docking Studies of Some Tetrahydropyrimidine Derivatives as Possible Fascin Inhibitors

Eight derivatives of tetrahydropyrimidine scaffold were designed and prepared as hybrid compounds possessing the structural features of both monastrol as an anticancer drug and nifedipine as a fascin blocking agent. All of the compounds were evaluated for their cytotoxic potency and the ability to inhibit 4T1 breast cancer cells migration. Then, they were investigated in silico for their ability to inhibit the fascin protein using molecular docking simulation. The most potent compound was 4d and the weakest one was 4a according to the in vitro cytotoxicity assay. The corresponding IC₅₀ values were 193.70 and 248.75 μm , respectively. The least cytotoxic compound ( 4a ) was one of the strongest ones in binding to the fascin binding site according to the molecular docking results. 4a and 4e inhibited the 4T1 cells migration better than other compounds. They were more potent than nifedipine in inhibiting the migration process. In silico studies proved 4h to be the most potent fascin inhibitor in terms of ΔG_bind although it was not inhibiting migration. The controversy between the in vitro and in silico results may cancel the theory of the involvement of the fascin inhibition in the migration inhibition. However, the considerable antimigratory effects of some of the synthesized compounds encourage performing further in vivo experiments to introduce novel tumor metastasis inhibitors.