Antimalarial Development Research Articles

Antiplasmodial Activity of Ketotifen-Artemether-Lumefantrine on Plasmodium Berghei Infected Mice

Introduction: The development of new antimalarial drugs is time-consuming and costly, thus repurposing of drugs with initial indications for possible antimalarial indication is imperative. This study assessed the antiplasmodial effect of ketotifen (KT) in combination with artemether/lumefantrine (A/L) in Plasmodium bergei infected mice. Materials and Methods: Adult mice (25-30g) were parasitized with Plasmodium berghei, grouped and treated per oral (p.o) with KT (0.1mg/kg), A/L (2.3/13.7mg/kg) and KT/A/L daily in curative, suppressive and prophylactic studies. The negative control (NC) and the positive control (PC) were treated daily p.o with normal saline (0.2mL) and chloroquine (CQ) (10mg/kg) for 4 days respectively. After treatment, blood samples were collected and assessed for percentage parasitemia level, hematological and lipid parameters. Results: The curative, suppressive and prophylactic studies showed significant decreases in percentage parasitemia levels at KT (0.1mg/kg) (p<0.01), A/L (2.3/13.7 mg/kg) (p<0.001) and KT/A/L (p<0.0001) when compared to negative control. Significant increases in mean survival times occurred at KT (0.1 mg/kg) (p<0.01), A/L (2.3/13.7mg/kg) (p<0.001) and A/L/T (p<0.0001) when compared to negative control. Significant increases in pack cell volume, red blood cells, hemoglobin, high density lipoprotein cholesterol levels with significant decreases in total cholesterol, white blood cells, low density lipoprotein cholesterol and triglyceride levels at KT (28.6 mg/kg) (p<0.05), A/L (2.3/13.7mg/kg) (p<0.01) and KT/A/L (p<0.001) when compared to negative control. Conclusion: KT may be repurposed in combination with A/L for malaria treatment.

Characterisation of naturally occurring isothiocyanates as glutathione reductase inhibitors

Glutathione reductase (GR), an essential antioxidant enzyme against oxidative stress, has become an attractive drug target for the development of anticancer and antimalarial drugs. In this regard, we evaluated the naturally occurring isothiocyanates as promising GR inhibitors and elucidated the mechanism of action. It was found that benzyl isothiocyanate (BITC) and phenethyl isothiocyanate (PEITC) inhibited yeast GR (yGR) and human GR (hGR) in a time- and concentration-dependent manner. The Ki and kinact of BITC against yGR were determined to be 259.87 µM and 0.0266 min−1, respectively. The GR inhibition occurred only in the presence of NADPH and persisted after extensive dialysis. The tandem mass spectrometric analysis revealed that Cys61 rather than Cys66 at the active site of yGR was mono-benzyl thiocarbamoylated by BITC. Inhibition of intracellular GR by BITC and PEITC in cultured cancer cells was also observed. BITC and PEITC were evaluated as competitive and irreversible inhibitors of GR.

Эффективность ингибиторов теломеразы против малярийных паразитов in vivo

One of the most dangerous causative agents of malaria is Plasmodium falciparum, transmitted by various Anopheline mosquitoes. Due to widespread drug resistance to practically all antimalarials, novel and effective drugs to manage this important disease are urgently required. In this study we evaluated the antimalarial activity of a series of 14 compounds from the inhibitors of the telomerase group. For in vivo studies we used P. berghei strain NK 65 in white unbread mice. The most antimalarial activity was shown by Imatinib, Phosphazide and Imetelstat. We found that Imatinib is the most potent compound and therefore can serve as a potential lead for the development of new antimalarial drug. Key words: malaria, drug resistance, inhibitors of telomerase, imatinib, chemotherapy of malaria

Plasmodium falciparum GCN5 acetyltransferase follows a novel proteolytic processing pathway that is essential for its function.

The pathogenesis of human malarial parasite Plasmodium falciparum is interlinked with its timely control of gene expression during its complex life cycle. In this organism, gene expression is partially controlled through epigenetic mechanisms, the regulation of which is, hence, of paramount importance to the parasite. The P. falciparum (Pf)-GCN5 histone acetyltransferase (HAT), an essential enzyme, acetylates histone 3 and regulates global gene expression in the parasite. Here, we show the existence of a novel proteolytic processing for PfGCN5 that is crucial for its activity in vivo We find that a cysteine protease-like enzyme is required for the processing of PfGCN5 protein. Immunofluorescence and immuno-electron microscopy analysis suggest that the processing event occurs in the vicinity of the digestive vacuole of the parasite following its trafficking through the classical ER-Golgi secretory pathway, before it subsequently reaches the nucleus. Furthermore, blocking of PfGCN5 processing leads to the concomitant reduction of its occupancy at the gene promoters and a reduced H3K9 acetylation level at these promoters, highlighting the important correlation between the processing event and PfGCN5 activity. Altogether, our study reveals a unique processing event for a nuclear protein PfGCN5 with unforeseen role of a food vacuolar cysteine protease. This leads to a possibility of the development of new antimalarials against these targets.This article has an associated First Person interview with the first author of the paper.

ATP gatekeeper of Plasmodium protein kinase may provide the opportunity to develop selective antimalarial drugs with multiple targets

Malaria is one of the most devastating infectious diseases that caused millions of clinical cases annually despite decades of prevention efforts. Recent cases of Plasmodium falciparum resistance against the only remaining class of effective antimalarial (artemisinin) in South East Asia may soon pose a significant threat. Hence, the identification of new antimalarial compounds with a novel mode of action is necessary to curb this problem. Protein kinase has been implicated as a valid target for drug development in diseases such as cancer and diabetes in humans. A similar approach is now recognized for the treatment of protozoan-related disease including malaria. Few Plasmodium protein kinases that are not only crucial for their survival but also have unique structural features have been identified as a potential target for drug development. In this review, studies on antimalarial drug development exploiting the size of Plasmodium protein kinase ATP gatekeeper over the past 15 years are mainly discussed. The ATP-binding site of Plasmodium protein kinases such as Pf CDPK1, Pf CDPK4, Pf PKG, Pf PK7, and Pf PI4K showed great potential for selective and multi-target inhibitions owing to their smaller or unique ATP-gatekeeper amino acid subunits compared to that of human protein kinase. Hence it is a feasible solution to identify a new class of active antimalarial agents with a novel mode of action and longer clinical life-span.

Implication of serine-decarboxylase-phosphoethanolamine-methyltransferase Pathway and phosphoethanolamine-methyltransferase in Malaria abolition

The growing resistance to current antimalarial drugs is a major concern for global public health, demands the novel essential regulatory pathway of plasmodium to be targeted for new potent antimalarial development. The biological processes that regulate both growth and gametocytogenesis of plasmodium still remain unknown. Identification and thorough understanding of such pathways is crucial to the development of a new generation of dual activity antimalarials that can inhibit both infection and transmission. There one pathway responsible for phosphatidylcholine (PC) a phospholipid biosynthesis in Bacteria, eukaryotes and plants through different routes, has also been elucidated in plasmodium. Plasmodium normally synthesizes PC for membrane development from choline through CDP-choline route but at infection stage in host it needs faster development of PC abundantly for membrane development from serine of the host blood through plant like serine-decarboxylase-phosphoethanolamine-methyltransferase (SDPM) alternate pathway absent in human host. Phosphoethanolamine methyltransferase (PMT) an enzyme crucial for catalyzing trimethylation, a rate limiting step to synthesize PC is a promising target for research on a novel class of antimalarials. In this review, we have emphasized development of PC biosynthesis through SDPM pathway and the significance of PC in Plasmodium to provide novel directions in which research might be most beneficial. We also focused on important perspectives and applicability of PMTs as therapeutic target for structure-based drug designing for PMT inhibitor discovery as antimalarials.

Antimalarial Phytochemicals Identification from Euphorbia Hirta against Plasmepsin Protease: an In Silico Approach.

Aspartic protease found in plasmodium parasites such as plasmepsin I, II and IV plays an important role in the degradation of hemoglobin. The studies have shown that effective drug must be able to inhibit more than one type of plasmepsin to avoid further growth of parasites and to prevent resistance of drug. Therefore, plasmepsins are believed to be excellent drug target for malarial disease. Extract of the plant Euphorbia hirta has been proved to exert antimalarial activity. However, molecular mechanism of this activity was not described. The aim of present investigation is to identify antimalarial phytochemicals of Euphorbia hirta as plasmepsin protease inhibitors using an in silico approach. Docking studies were performed on three different protein targets plasmepsin I, II, and IV using iGEMDOCK. ADME and bioactivity predictions were done using molinspiration online tool. Toxicity studies were performed using ProTox-II online tool. In the docking studies seven compounds showed significant inhibitory activity with low docking score as compared to standard drug artemisinin. Six compounds showed no violations as per Lipinski rule. Bioactivity prediction states that all the compounds may act through enzyme inhibition. The results of in silico studies suggest that out of the eleven selected phytochemicals isorhamnetin and pinocembrin have more drug likeliness properties and lesser in silico toxicity with more binding affinity than artemisinin on all receptors. These findings indicate that isorhamnetin and pinocembrin have promising potential for development of antimalarial drug as plasmepsin inhibitors.

Impact of Field Isolate Identified Nonsynonymous Single Nucleotide Polymorphisms on Plasmodium falciparum Equilibrative Nucleoside Transporter 1 Inhibitor Efficacy.

Plasmodium falciparum causes the most severe form of malaria and causes approximately 500 000 deaths per year. P. falciparum parasites resistant to current antimalarial treatments are spreading. Therefore, it is imperative to develop new antimalarial drugs. Malaria parasites are purine auxotrophic. They rely on purine import from the host erythrocyte via Equilibrative Nucleoside Transporters (ENTs). Recently, inhibitors of the P. falciparum ENT1 (PfENT1) that inhibit proliferation of malaria parasites in culture have been identified as promising starting points for antimalarial drug development. Genome sequencing of P. falciparum field isolates has identified nonsynonymous single nucleotide polymorphisms (SNPs) in the gene encoding PfENT1. Here we evaluate the impact of these PfENT1 SNPs on purine substrate affinity and inhibitor efficacy. We expressed each PfENT1-SNP in Saccharomyces cerevisiae. Using PfENT1-SNP-expressing yeast, we characterized the PfENT1 purine substrate affinity using radiolabeled substrate uptake inhibition experiments. Four of the 13 SNPs altered affinity for one or more purines by up to 7-fold. Three of the SNPs reduced the potency of a subset of the inhibitors by up to 7-fold. One SNP, Q284E, reduced the potency of all six inhibitor chemotypes. We tested drug efficacy in available parasite strains containing PfENT1 SNPs. While PfENT1-SNP-expressing yeast had decreased sensitivity to PfENT1 inhibitors, parasite strains containing SNPs showed similar or more potent inhibition of proliferation with all PfENT1 inhibitors. Thus, parasite strains bearing PfENT1 SNPs are not resistant to these PfENT1 inhibitors. This supports PfENT1 as a promising target for further development of novel antimalarial drugs.

Discovery of a new predominant cytosine DNA modification that is linked to gene expression in malaria parasites.

DNA cytosine modifications are key epigenetic regulators of cellular processes in mammalian cells, with their misregulation leading to varied disease states. In the human malaria parasite Plasmodium falciparum, a unicellular eukaryotic pathogen, little is known about the predominant cytosine modifications, cytosine methylation (5mC) and hydroxymethylation (5hmC). Here, we report the first identification of a hydroxymethylcytosine-like (5hmC-like) modification in P. falciparum asexual blood stages using a suite of biochemical methods. In contrast to mammalian cells, we report 5hmC-like levels in the P. falciparum genome of 0.2–0.4%, which are significantly higher than the methylated cytosine (mC) levels of 0.01–0.05%. Immunoprecipitation of hydroxymethylated DNA followed by next generation sequencing (hmeDIP-seq) revealed that 5hmC-like modifications are enriched in gene bodies with minimal dynamic changes during asexual development. Moreover, levels of the 5hmC-like base in gene bodies positively correlated to transcript levels, with more than 2000 genes stably marked with this modification throughout asexual development. Our work highlights the existence of a new predominant cytosine DNA modification pathway in P. falciparum and opens up exciting avenues for gene regulation research and the development of antimalarials.

Natural Product Inspired Novel Indole based Chiral Scaffold Kills Human Malaria Parasites via Ionic Imbalance Mediated Cell Death

Natural products offer an abundant source of diverse novel scaffolds that inspires development of next generation anti-malarials. With this vision, a library of scaffolds inspired by natural biologically active alkaloids was synthesized from chiral bicyclic lactams with steps/scaffold ratio of 1.7:1. On evaluation of library of scaffolds for their growth inhibitory effect against malaria parasite we found one scaffold with IC50 in low micro molar range. It inhibited parasite growth via disruption of Na+ homeostasis. P-type ATPase, PfATP4 is responsible for maintaining parasite Na+ homeostasis and is a good target for anti-malarials. Molecular docking with our scaffold showed that it fits well in the binding pocket of PfATP4. Moreover, inhibition of Na+-dependent ATPase activity by our potent scaffold suggests that it targets parasite by inhibiting PfATP4, leading to ionic imbalance. However how ionic imbalance attributes to parasite’s death is unclear. We show that ionic imbalance caused by scaffold 7 induces autophagy that leads to onset of apoptosis in the parasite evident by the loss of mitochondrial membrane potential (ΔΨm) and DNA degradation. Our study provides a novel strategy for drug discovery and an insight into the molecular mechanism of ionic imbalance mediated death in malaria parasite.

Histone deacetylase inhibitors with high in vitro activities against Plasmodium falciparum isolates collected from Gabonese children and adults

Histone deacetylase (HDAC) enzymes are targets for the development of antimalarial drugs with a different mode of action to established antimalarials. Broad-spectrum HDAC-inhibitors show high potency against Plasmodium falciparum, but displayed some toxicity towards human cells. Inhibitors of human HDAC6 are new drug candidates with supposed reduced toxicity to human cells and favorable activities against laboratory P. falciparum strains. We investigated the potency of 12 peptoid-based HDAC-inhibitors against asexual stages of P. falciparum clinical isolates. Parasites representing different genetic backgrounds were isolated from adults and children with uncomplicated malaria in Gabon. Clinical studies on (non-HDAC-inhibitors) antimalarials, moreover, found lower drug efficacy in children, mainly attributed to acquired immunity with age in endemic areas. Therefore, we compared the in vitro sensitivity profiles of adult- and child-derived isolates to antimalarials (HDAC and standard drugs). All HDAC-inhibitors showed 50% inhibitory concentrations at nanomolar ranges with higher activities than the FDA approved reference HDAC-inhibitor SAHA. We propose peptoid-based HDAC6-inhibitors to be lead structures for further development as antimalarial chemotherapeutics. Our results further suggest no differences in activity of the tested antimalarials between P. falciparum parasites isolated from children and adults.

Epigenetic reader complexes of the human malaria parasite, Plasmodium falciparum.

Epigenetic regulatory mechanisms are central to the development and survival of all eukaryotic organisms. These mechanisms critically depend on the marking of chromatin domains with distinctive histone tail modifications (PTMs) and their recognition by effector protein complexes. Here we used quantitative proteomic approaches to unveil interactions between PTMs and associated reader protein complexes of Plasmodium falciparum, a unicellular parasite causing malaria. Histone peptide pull-downs with the most prominent and/or parasite-specific PTMs revealed the binding preference for 14 putative and novel reader proteins. Amongst others, they highlighted the acetylation-level-dependent recruitment of the BDP1/BDP2 complex and identified an PhD-finger protein (PHD 1, PF3D7_1008100) that could mediate a cross-talk between H3K4me2/3 and H3K9ac marks. Tagging and interaction proteomics of 12 identified proteins unveiled the composition of 5 major epigenetic complexes, including the elusive TBP-associated-factor complex as well as two distinct GCN5/ADA2 complexes. Furthermore, it has highlighted a remarkable degree of interaction between these five (sub)complexes. Collectively, this study provides an extensive inventory of PTM-reader interactions and composition of epigenetic complexes. It will not only fuel further explorations of gene regulation amongst ancient eukaryotes, but also provides a stepping stone for exploration of PTM-reader interactions for antimalarial drug development.

Recent Advances in System Based Study for Anti-Malarial Drug Development Process

Presently, malaria is one of the most prevalent and deadly infectious disease across Africa, Asia, and America that has now started to spread in Europe. Despite large research being carried out in the field, still, there is a lack of efficient anti-malarial therapeutics. In this paper, we highlight the increasing efforts that are urgently needed towards the development and discovery of potential antimalarial drugs, which must be safe and affordable. The new drugs thus mentioned are also able to counter the spread of malaria parasites that have been resistant to the existing agents. The main objective of the review is to highlight the recent development in the use of system biologybased approaches towards the design and discovery of novel anti-malarial inhibitors. A huge literature survey was performed to gain advance knowledge about the global persistence of malaria, its available treatment and shortcomings of the available inhibitors. Literature search and depth analysis were also done to gain insight into the use of system biology in drug discovery and how this approach could be utilized towards the development of the novel anti-malarial drug. The system-based analysis has made easy to understand large scale sequencing data, find candidate genes expression during malaria disease progression further design of drug molecules those are complementary of the target proteins in term of shape and configuration. The review article focused on the recent computational advances in new generation sequencing, molecular modeling, and docking related to malaria disease and utilization of the modern system and network biology approach to antimalarial potential drug discovery and development.

Gene knockdown in malaria parasites via non-canonical RNAi.

The lack of endogenous RNAi machinery in the malaria parasite Plasmodium hampers gene annotation and hence antimalarial drug and vaccine development. Here, we engineered rodent Plasmodium berghei to express a minimal, non-canonical RNAi machinery that solely requires Argonaute 2 (Ago2) and a modified short hairpin RNA, so-called AgoshRNA. Using this strategy, we achieved robust and specific gene knockdown throughout the entire parasite life cycle. We also successfully silenced the endogenous gene perforin-like protein 2, phenocopying a full gene knockout. Transcriptionally restricting Ago2 expression to the liver stage further enabled us to perform a stage-specific gene knockout. The RNAi-competent Plasmodium lines reported here will be a valuable resource for loss-of-function phenotyping of the many uncharacterized genes of Plasmodium in low or high throughput, without the need to engineer the target gene locus. Thereby, our new strategy and transgenic Plasmodium lines will ultimately benefit the discovery of urgently needed antimalarial drug and vaccine candidates. Generally, the ability to render RNAi-negative organisms RNAi-competent by mere introduction of two components, Ago2 and AgoshRNA, is a unique paradigm that should find broad applicability in other species.

Antiplasmodial, Hepatic and Nephritic Effects of Fractions of Methanol Leaf Extract of Glyphaea brevis in Plasmodium berghei-Infected Mice

This study evaluated the antiplasmodial, hepatic and nephritic effects of fractions of Glyphaea brevis methanol leaf extract in P. berghei infected mice. Mice weighing between 15-30 g were infested intraperitoneally with 0.2ml plasmodium infected blood and left for 3 hours before treatment. Infected test groups were treated via oral route of administration with varying doses (200, 300 and 400 mg/kg body weight) of ethylacetate, N-butanol and residual aqueous portion fractions of the Glyphaea brevis methanol extract and Artemisinin (5 mg/kg b.wt) for four days. N-butanol fraction showed the highest antiplasmodial activity (76.64%), followed by residual aqueous portion (73.25%) and ethylacetate (72.99%); Artemisinin has 86.13%. Serum bilirubin (total and conjugated) concentrations of the untreated group (0.82 ± 0.20, 0.51 ± 0.12) were significantly lower (P<0.05) than those in the infected group treated with 300 mg/kg of the residual aqueous portion (1.36 ± 0.20, 0.76 ± 0.05) respectively. Serum albumin levels showed significant (P<0.05) increase in all the groups treated compared to the positive control. Serum total protein, urea and creatinine levels of test groups were not significantly (P>0.05) different from the positive control group. Conclusively, Glyphaea brevis has substantial antiplasmodial activity and could provide a lead for new antimalarial drug development.

Identification of Small Molecules Disrupting the Ubiquitin Proteasome System in Malaria.

The ubiquitin proteasome system (UPS) is one of the main proteolytic pathways in eukaryotic cells, playing an essential role in key cellular processes such as cell cycling and signal transduction. Changes in some of the components of this pathway have been implicated in various conditions, including cancer and infectious diseases such as malaria. The success of therapies based on proteasome inhibitors has been shown in human clinical trials. In addition to its proven tractability, the essentiality of the Plasmodium falciparum UPS underlines its potential as a source of targets to identify new antimalarial treatments. Two assays, previously developed to quantify the parasite protein ubiquitylation levels in a high throughput format, have been used to identify compounds that inhibit parasite growth by targeting P. falciparum UPS. Among the positive hits, specific inhibitors of the P. falciparum proteasome have been identified and characterized. Hits identified using this approach may be used as starting points for development of new antimalarial drugs. They may also be used as tools to further understand proteasome function and to identify new targets in P. falciparum UPS.

Plasmodial enzymes in metabolic pathways as therapeutic targets and contemporary strategies to discover new antimalarial drugs: a review

Malaria continues to pose imminent threat to the world population, as the mortality rate associated with this disease remains high. Current treatment relies on antimalarial drugs such as Artemisinin Combination Therapy (ACT) are still effective throughout the world except in some places, where ACT-resistance has been reported, thus necessitating novel approaches to develop new anti-malarial therapy. In the light of emerging translational research, several plasmodial targets, mostly proteins or enzymes located in the parasite’s unique organelles, have been extensively explored as potential candidates for the development of novel antimalarial drugs. By targeting the metabolic pathways in mitochondrion, apicoplast or cytoplasm of Plasmodium, the possibility to discover new drugs is tremendous, as they have potentials as antimalarial therapeutic targets. This literature review summarizes pertinent information on plasmodial targets, especially enzymes involved in specific metabolic pathways, and the strategies used to discover new antimalarial drugs.

Chemical Genomic Profiling Unveils the in Vitro and in Vivo Antiplasmodial Mechanism of Açaí (Euterpe oleracea Mart.) Polyphenols.

Malaria remains a major detrimental parasitic disease in the developing world, with more than 200 million cases annually. Widespread drug-resistant parasite strains push for the development of novel antimalarial drugs. Plant-derived natural products are key sources of antimalarial molecules. Euterpe oleracea Martius (“açaí”) originates from Brazil and has anti-inflammatory and antineoplasic properties. Here, we evaluated the antimalarial efficacy of three phenolic fractions of açaí; total phenolics (1), nonanthocyanin phenolics (2), and total anthocyanins (3). In vitro, fraction 2 moderately inhibited parasite growth in chloroquine-sensitive (HB3) and multiresistant (Dd2) Plasmodium falciparum strains, while none of the fractions was toxic to noncancer cells. Despite the limited activity in vitro, the oral treatment with 20 mg/kg of fraction 1 reduced parasitemia by 89.4% in Plasmodium chabaudi-infected mice and prolonged survival. Contrasting in vitro and in vivo activities of 1 suggest key antiplasmodial roles for polyphenol metabolites rather than the fraction itself. Finally, we performed haploinsufficiency chemical genomic profiling (HIP) utilizing heterozygous Saccharomyces cerevisiae deletion mutants to identify molecular mechanisms of açaí fractions. HIP results indicate proteostasis as the main cellular pathway affected by fraction 2. These results open avenues to develop açaí polyphenols as potential new antimalarial candidates.

Molecular docking and dynamics studies on novel benzene sulfonamide substituted pyrazole-pyrazoline analogues as potent inhibitors of Plasmodium falciparum Histo aspartic protease

Malaria is the major health issue in African, Asian and Mediterranean regions of the world. Due to the emerging resistance by the parasites and mosquitoes for the current medications and insecticides, respectively, the malaria free human world can be attained only by the novel design and development of new anti-malarial drugs. Hence, we attempted to carry out in silico screening of benzene sulfonamide substituted pyrazole-pyrazoline series against Histo aspartic protease. Our results reveal that the 65% of the data set with the free binding energy in the range of –11.58 to –11.21 kcal/mol, which is categorized as ‘high scoring’. Ligands are docked with the catalytic residues Asp 215, Ser 75, Thr 33 and Ala 217, respectively. Molecular dynamic simulation study of free enzyme and the enzyme complex with 4-(5-(4-methoxyphenyl)-1’phenyl-3’-(p-tolyl)-3,4-1’H,2H-[3,4’-bipyrazol]-2-yl)benezenesulfonamide indicated structural stability. The trajectory analysis of complex reveals that the HAP–ligand complex is more stable than the free HAP. We are of the opinion that our results will be useful for designing potential anti-malarial compounds.AbbreviationsADTauto dock toolsBSPPbenzene sulfonamide substituted pyrazole-pyrazolineCQchloroquineHAPhisto aspartic proteaseKKelvinMDmolecular dockingMM/PBSAmolecular mechanics/Poisson Boltzmann surface areaNVTnormal volume and temperatureNPTnormal pressure and temperatureNsnanosecondsPDBprotein data bank.pdbprogram data base formatP. falciparumPlasmodium falciparumPspicosecondsPMsplasmepsinsP. vivaxPlasmodium vivaxRgradius of gyrationRMSDroot mean square deviationRMSFroot mean square fluctuationWHOWorld Health OrganizationCommunicated by Ramaswamy H. Sarma

Computational and experimental elucidation of Plasmodium falciparum phosphoethanolamine methyltransferase inhibitors: Pivotal drug target.

IntroductionPlasmodium falciparum synthesizes phosphatidylcholine for the membrane development through serine decarboxylase–phosphoethanolamine methyltransferase pathway for growth in human host. Phosphoethanolamine-methyltransferase (PfPMT) is a crucial enzyme for the synthesis of phosphocholine which is a precursor for phosphatidylcholine synthesis and is considered as a pivotal drug target as it is absent in the host. The inhibition of PfPMT may kill malaria parasite and hence is being considered as potential target for rational antimalarial drug designing.MethodsIn this study, we have used computer aided drug designing (CADD) approaches to establish potential PfPMT inhibitors from Asinex compound library virtually screened for ADMET and the docking affinity. The selected compounds were tested for in-vitro schizonticidal, gametocidal and cytotoxicity activity. Nontoxic compounds were further studied for PfPMT enzyme specificity and antimalarial efficacy for P. berghei in albino mice model.ResultsOur results have identified two nontoxic PfPMT competitive inhibitors ASN.1 and ASN.3 with better schizonticidal and gametocidal activity which were found to inhibit PfPMT at IC50 1.49μM and 2.31μM respectively. The promising reduction in parasitaemia was found both in orally (50 & 10 mg/kg) and intravenous (IV) (5& 1 mg/kg) however, the better growth inhibition was found in intravenous groups.ConclusionWe report that the compounds containing Pyridinyl-Pyrimidine and Phenyl-Furan scaffolds as the potential inhibitors of PfPMT and thus may act as promising antimalarial inhibitor candidates which can be further optimized and used as leads for template based antimalarial drug development.