Brazilian malaria molecular targets (BraMMT): selected receptors for virtual high-throughput screening experiments.

BACKGROUND: Owing to increased spending on pharmaceuticals since 2010, discussions about rising costs for the development of new medical technologies have been focused on the pharmaceutical industry. Computational techniques have been developed to reduce costs associated with new drug development. Among these techniques, virtual high-throughput screening (vHTS) can contribute to the drug discovery process by providing tools to search for new drugs with the ability to bind a specific molecular target. OBJECTIVES: In this context, Brazilian malaria molecular targets (BraMMT) was generated to execute vHTS experiments on selected molecular targets of Plasmodium falciparum. METHODS: In this study, 35 molecular targets of P. falciparum were built and evaluated against known antimalarial compounds. FINDINGS: As a result, it could predict the correct molecular target of market drugs, such as artemisinin. In addition, our findings suggested a new pharmacological mechanism for quinine, which includes inhibition of falcipain-II and a potential new antimalarial candidate, clioquinol. MAIN CONCLUSIONS: The BraMMT is available to perform vHTS experiments using OCTOPUS or Raccoon software to improve the search for new antimalarial compounds. It can be retrieved from www.drugdiscovery.com.br or download of Supplementary data.

Successful application of virtual screening and molecular dynamics simulations against antimalarial molecular targets.

The main challenge in the control of malaria has been the emergence of drug-resistant parasites. The presence of drug-resistant Plasmodium sp. has raised the need for new antimalarial drugs. Molecular modelling techniques have been used as tools to develop new drugs. In this study, we employed virtual screening of a pyrazol derivative (Tx001) against four malaria targets: plasmepsin-IV, plasmepsin-II, falcipain-II, and PfATP6. The receiver operating characteristic curves and area under the curve (AUC) were established for each molecular target. The AUC values obtained for plasmepsin-IV, plasmepsin-II, and falcipain-II were 0.64, 0.92, and 0.94, respectively. All docking simulations were carried out using AutoDock Vina software. The ligand Tx001 exhibited a better interaction with PfATP6 than with the reference compound (-12.2 versus -6.8 Kcal/mol). The Tx001-PfATP6 complex was submitted to molecular dynamics simulations in vacuum implemented on an NAMD program. The ligand Tx001 docked at the same binding site as thapsigargin, which is a natural inhibitor of PfATP6. Compound TX001 was evaluated in vitro with a P. falciparum strain (W2) and a human cell line (WI-26VA4). Tx001 was discovered to be active against P. falciparum (IC50 = 8.2 µM) and inactive against WI-26VA4 (IC50 > 200 µM). Further ligand optimisation cycles generated new prospects for docking and biological assays.

Structure-based drug design studies of the interactions of ent-kaurane diterpenes derived from Wedelia paludosa with the Plasmodium falciparum sarco/endoplasmic reticulum Ca²âº-ATPase PfATP6.

Malaria is responsible for more deaths around the world than any other parasitic disease. Due to the emergence of strains that are resistant to the current chemotherapeutic antimalarial arsenal, the search for new antimalarial drugs remains urgent though hampered by a lack of knowledge regarding the molecular mechanisms of artemisinin resistance. Semisynthetic compounds derived from diterpenes from the medicinal plant Wedelia paludosa were tested in silico against the Plasmodium falciparum Ca2+-ATPase, PfATP6. This protein was constructed by comparative modelling using the three-dimensional structure of a homologous protein, 1IWO, as a scaffold. Compound 21 showed the best docking scores, indicating a better interaction with PfATP6 than that of thapsigargin, the natural inhibitor. Inhibition of PfATP6 by diterpene compounds could promote a change in calcium homeostasis, leading to parasite death. These data suggest PfATP6 as a potential target for the antimalarial ent-kaurane diterpenes.

Antiplasmodial activity of coumarins isolated from Polygala boliviensis: in vitro and in silico studies.

Polygala boliviensis is found in the Brazilian semiarid region. This specie is little chemically and biologically studied. Polygala spp. have different metabolites, especially coumarins. Studies indicate that coumarins have antimalarial potential, denoting the importance of researching new active compounds from plants, since the resistance of Plasmodium strains to conventional therapy has increased. The present study aimed to evaluate the antiplasmodial activity of auraptene and poligalen against a chloroquine-resistant strain of Plasmodium falciparum. Coumarins were isolated from P. boliviensis by open column chromatography and identified by Nuclear Magnetic Resonance Spectroscopy. A cytotoxicity assay was carried out using MTT test, and the in vitro antiplasmodial activity was evaluated using the W2 strain. The antiplasmodial activity results found were IC50=0.171 ± 0.016 for auraptene and 0.164 ± 0.012 for poligalen; the selectivity indexes were 78.71 and 609.76, respectively. Inverse virtual screening in the BRAMMT database by OCTOPUS 1.2 was applied to coumarins to find potential P. falciparum targets and showed higher affinity energy of auraptene for purine nucleoside phosphorylase (PfPNP) and of poligalen for dihydroorotate dehydrogenase (PfDHODH). Molecular Dynamics studies (MD and MM-GBSA) approach were applied to calculate binding energies against selected P. falciparum targets and showed that all coumarins were stable at the binding site during simulations. Furthermore, energies were favorable for complexation. This is the first report of auraptene in P. boliviensis species and of in vitro antiplasmodial activity of auraptene and poligalen. In silico studies indicated that the mechanism of action of coumarins is the inhibition of PfPNP and PfDHODH.Communicated by Ramaswamy H. Sarma.

A novel antiplasmodial compound: integration of in silico and in vitro assays.

Malaria is a disease caused by Plasmodium genus. which P. falciparum is responsible for the most severe form of the disease, cerebral malaria. In 2018, 405,000 people died of malaria. Antimalarial drugs have serious adverse effects and limited efficacy due to multidrug-resistant strains. One way to overcome these limitations is the use of computational approaches for prioritizing candidates to phenotypic assays and/or in vitro assays against validated targets. Plasmodium falciparum Enoyl-ACP reductase (PfENR) is noteworthy because it catalyzes the rate-limiting step of the biosynthetic pathway of fatty acid. Thus, the study aimed to identify potential PfENR inhibitors by ligand (2D molecular similarity and pharmacophore models) and structure-based virtual screening (molecular docking). 2D similarity-based virtual screening using Tanimoto Index (> 0.45) selected 29,236 molecules from natural products subset available in ZINC database (n = 181,603). Next, 10 pharmacophore models for PfENR inhibitors were generated and evaluated based on the internal statistical parameters from GALAHAD™ and ROC/AUC curve. These parameters selected a suitable pharmacophore model with one hydrophobic center and two hydrogen bond acceptors. The alignment of the filtered molecules on best pharmacophore model resulted in the selection of 10,977 molecules. These molecules were directed to the docking-based virtual screening by AutoDock Vina 1.1.2 program. These strategies selected one compound to phenotypic assays against parasite. ZINC630259 showed EC50 = 0.12 ± 0.018 µM in antiplasmodial assays and selective index similar to other antimalarial drugs. Finally, MM/PBSA method showed stability of molecule within PfENR binding site (ΔGbinding=-57.337 kJ/mol).Communicated by Ramaswamy H. Sarma.

In vitro and in silico assessment of new beta amino ketones with antiplasmodial activity.

BACKGROUND: Based on the current need for new drugs against malaria, our study evaluated eight beta amino ketones in silico and in vitro for potential antimalarial activity. METHODS: Using the Brazilian Malaria Molecular Targets (BraMMT) and OCTOPUS® software programs, the pattern of interactions of beta-amino ketones was described against different proteins of P. falciparum and screened to evaluate their physicochemical properties. The in vitro antiplasmodial activities of the compounds were evaluated using a SYBR Green-based assay. In parallel, in vitro cytotoxic data were obtained using the MTT assay. RESULTS: Among the eight compounds, compound 1 was the most active and selective against P. falciparum (IC50 = 0.98 µM; SI > 60). Six targets were identified in BraMMT that interact with compounds exhibiting a stronger binding energy than the crystallographic ligand: P. falciparum triophosphate phosphoglycolate complex (1LYX), P. falciparum reductase (2OK8), PfPK7 (2PML), P. falciparum glutaredoxin (4N0Z), PfATP6, and PfHT. CONCLUSIONS: The physicochemical properties of compound 1 were compatible with the set of criteria established by the Lipinski rule and demonstrated its potential as a drug prototype for antiplasmodial activity.

Rational-Based Discovery of Novel ß-Carboline Derivatives as Potential Antimalarials: From In Silico Identification of Novel Targets to Inhibition of Experimental Cerebral Malaria.

Malaria is an infectious disease widespread in underdeveloped tropical regions. The most severe form of infection is caused by Plasmodium falciparum, which can lead to development of cerebral malaria (CM) and is responsible for deaths and significant neurocognitive sequelae throughout life. In this context and considering the emergence and spread of drug-resistant P. falciparum isolates, the search for new antimalarial candidates becomes urgent. ß-carbolines alkaloids are good candidates since a wide range of biological activity for these compounds has been reported. Herein, we designed 20 chemical entities and performed an in silico virtual screening against a pool of P. falciparum molecular targets, the Brazilian Malaria Molecular Targets (BRAMMT). Seven structures showed potential to interact with PfFNR, PfPK7, PfGrx1, and PfATP6, being synthesized and evaluated for in vitro antiplasmodial activity. Among them, compounds 3−6 and 10 inhibited the growth of the W2 strain at µM concentrations, with low cytotoxicity against the human cell line. In silico physicochemical and pharmacokinetic properties were found to be favorable for oral administration. The compound 10 provided the best results against CM, with important values of parasite growth inhibition on the 5th day post-infection for both curative (67.9%) and suppressive (82%) assays. Furthermore, this compound was able to elongate mice survival and protect them against the development of the experimental model of CM (>65%). Compound 10 also induced reduction of the NO level, possibly by interaction with iNOS. Therefore, this alkaloid showed promising activity for the treatment of malaria and was able to prevent the development of experimental cerebral malaria (ECM), probably by reducing NO synthesis.

Synthesis of Novel 1,2,3-Triazole Derivatives of Isocoumarins and 3,4-Dihydroisocoumarin with Potential Antiplasmodial Activity In Vitro.

BACKGROUND: Malaria greatly affects the world health, having caused more than 228 million cases only in 2018. The emergence of drug resistance is one of the main problems in its treatment, demonstrating the need for the development of new antimalarial drugs. OBJECTIVE: Synthesis and in vitro antiplasmodial evaluation of triazole compounds derived from isocoumarins and a 3,4-dihydroisocoumarin. METHODS: The compounds were synthesized in 4 to 6-step reactions with the formation of the triazole ring via the Copper(I)-catalyzed 1,3-dipolar cycloaddition between isocoumarin or 3,4- dihydroisocoumarin azides and terminal alkynes. This key reaction provided compounds with an unprecedented connection of isocoumarin or 3,4-dihydroisocoumarin and the 1,2,3-triazole ring. The products were tested for their antiplasmodial activity against a Plasmodium falciparum chloroquine resistant and sensitive strains (W2 and 3D7, respectively). RESULTS: Thirty-one substances were efficiently obtained by the proposed routes with an overall yield of 25-53%. The active substances in the antiplasmodial test displayed IC50 values ranging from 0.68-2.89 µM and 0.85-2.07 µM against W2 and 3D7 strains, respectively. CONCLUSION: This study demonstrated the great potential of isocoumarin or 3,4-dihydroisocoumarin derivatives because practically all the tested substances were active against Plasmodium falciparum.

Identification of novel antiplasmodial compound by hierarquical virtual screening and in vitro assays.

Malaria is an infectious disease caused by protozoa of the genus Plasmodium spp. with approximately 219 million cases in 2017. P. falciparum is main responsible for the most severe form of the disease, cerebral malaria. Despite of public health impacts, chemotherapy against malaria is still limited due to the emergence of drug resistance cases used in monotherapy and combination therapies. Thus, the development of new antimalarial drugs becomes emergency. One way of achieve this goal is to explore essential and/or unique therapeutic targets of the parasite, or at least sufficiently different to ensure selective inhibition. Enoil-ACP reductase (ENR) is a NADH-dependent enzyme responsible for the limiting step of the type II fatty acid biosynthetic pathway (FAS II). Thus, pharmacophore and docking based virtual screening were applied to prioritize molecules for in vitro assays against P. falciparum W2 strain. The application of successive filters at OOCC database (n = 618) resulted in the identification of one molecule (13) (EC50 = 0.098 ± 0.021 µM) with similar biological activity to artemether. The molecule 13 is a typical drug repurposing case due to previous other approved therapeutic uses on Chinese medicine as a non-specific cholinergic antagonist, thus it could be accelerated the drug development process. Additionally, molecular dynamics studies were used to confirm stability of the molecular interactions identified by molecular docking. Thus, representative structures of P. falciparum ENR can be used in a study to propose new derivatives for evaluation of biological activity in vitro and in vivo. Communicated by Ramaswamy H. Sarma.

Antiplasmodial activity of sulfonylhydrazones: in vitro and in silico approaches.

Malaria is still a life-threatening public health issue, and the upsurge of resistant strains requires continuous generation of active molecules. In this work, 35 sulfonylhydrazone derivatives were synthesized and evaluated against Plasmodium falciparum chloroquine-sensitive (3D7) and resistant (W2) strains. The most promising compound, 5b, had an IC50 of 0.22 µM against W2 and was less cytotoxic and 26-fold more selective than chloroquine. The structure-activity relationship model, statistical analysis and molecular modeling studies suggested that antiplasmodial activity was related to hydrogen bond acceptor count, molecular weight and partition coefficient of octanol/water and displacement of frontier orbitals to the heteroaromatic ring beside the imine bond. This study demonstrates that the synthesized molecules with a simple scaffold allow the hit-to-lead process for new antimalarials to commence.

Curcumin-loaded nanocapsules: Influence of surface characteristics on technological parameters and potential antimalarial activity.

The present study aimed to develop nanocapsules (NCs) loaded with curcumin (CCM) using different coatings, comparing the effect of these coatings on physicochemical properties of NCs. NCs were prepared by interfacial deposition of performed polymer, using different polymers as coatings (P80, PEG, Chitosan and Eudragit RS100®) and then, characterized in detail by different techniques (AFM, FTIR, DSC, XRD, among others). In vitro studies were performed, evaluating the release profile, cytotoxicity and antimalarial activity of CCM-loaded NCs. Overall, all CCM-loaded NCs samples exhibited typical characteristics as nanometric size, coating-dependent zeta potential, acidic pH value, span values below 2, homogeneous morphology and CCM-distribution in pseudophases of type VI (for all of coatings). Experimental results showed that CCM remains stable in lipid-core of NCs, maintaining its physicochemical and biological properties after nanoencapsulation process. In vitro release assays showed that nanoencapsulation was an efficient strategy to controlled release of CCM and P80-coated NCs presented slowest CCM-release considering all nanoformulations tested. Still, CCM-loaded NCs presented no cytotoxic effect. Also, all CCM-loaded NCs showed a perceptible antimalarial activity independently of their coatings (anionic and cationic), with more expressive results for CS-coated NCs. In conclusion, findings for CCM-loaded NCs and their different coatings seem to be a promising strategy to improve your biological activity.

Dehydrobufotenin extracted from the Amazonian toad Rhinella marina (Anura: Bufonidae) as a prototype molecule for the development of antiplasmodial drugs.

BACKGROUND: The resistance against antimalarial drugs represents a global challenge in the fight and control of malaria. The Brazilian biodiversity can be an important tool for research and development of new medicinal products. In this context, toxinology is a multidisciplinary approach on the development of new drugs, including the isolation, purification, and evaluation of the pharmacological activities of natural toxins. The present study aimed to evaluate the cytotoxicity, as well as the antimalarial activity in silico and in vitro of four compounds isolated from Rhinella marina venom as potential oral drug prototypes. METHODS: Four compounds were challenged against 35 target proteins from P. falciparum and screened to evaluate their physicochemical properties using docking assay in Brazilian Malaria Molecular Targets (BraMMT) software and in silico assay in OCTOPUS® software. The in vitro antimalarial activity of the compounds against the 3D7 Plasmodium falciparum clones were assessed using the SYBR Green I based assay (IC50). For the cytotoxic tests, the LD50 was determined in human pulmonary fibroblast cell line using the [3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay. RESULTS: All compounds presented a ligand-receptor interaction with ten Plasmodium falciparum-related protein targets, as well as antimalarial activity against chloroquine resistant strain (IC50 = 3.44 µM to 19.11 µM). Three of them (dehydrobufotenine, marinobufagin, and bufalin) showed adequate conditions for oral drug prototypes, with satisfactory prediction of absorption, permeability, and absence of toxicity. In the cell viability assay, only dehydrobufotenin was selective for the parasite. CONCLUSIONS: Dehydrobufotenin revealed to be a potential oral drug prototype presenting adequate antimalarial activity and absence of cytotoxicity, therefore should be subjected to further studies.

Co-nanoencapsulation of antimalarial drugs increases their in vitro efficacy against Plasmodium falciparum and decreases their toxicity to Caenorhabditis elegans.

Drugs used for the treatment and prevention of malaria have resistance-related problems, making them ineffective for monotherapy. If properly associated, many of these antimalarial drugs may find their way back to the treatment regimen. Among the therapeutic arsenal, quinine (QN) is a second-line treatment for uncomplicated malaria but has side effects that limit its use. Curcumin (CR) is a natural compound with anti-plasmodial activities and low bioavailability. In this context, the aim of this work was to develop and characterize co-encapsulated QN + CR-loaded polysorbate-coated polymeric nanocapsules (NC-QC) to evaluate their activity on Plasmodium falciparum and the safety of the nanoformulations for Caenorhabditis elegans. NC-QC displayed a diameter of approximately 200 nm, a negative zeta potential and a slightly basic pH. The drugs are homogeneously distributed in the NCs in the amorphous form. Co-encapsulated NCs exhibited a significant reduction in P. falciparum parasitemia, better than QN/CR. The worms exposed to NC-QC showed higher survival and longevity and no decrease in their reproductive capacity compared to free and associated drugs. It was possible to prove that the NCs were absorbed orally by the worms using fluorescence microscopy. Co-encapsulation of QN and CR was effective against P. falciparum, minimizing the toxic effects caused by chronic exposure of the free drugs in C. elegans.

In vitro and in silico assessment of new beta amino ketones with antiplasmodial activity

ABSTRACT Background: Based on the current need for new drugs against malaria, our study evaluated eight beta amino ketones in silico and in vitro for potential antimalarial activity. Methods: Using the Brazilian Malaria Molecular Targets (BraMMT) and OCTOPUS® software programs, the pattern of interactions of beta-amino ketones was described against different proteins of P. falciparum and screened to evaluate their physicochemical properties. The in vitro antiplasmodial activities of the compounds were evaluated using a SYBR Green-based assay. In parallel, in vitro cytotoxic data were obtained using the MTT assay. Results: Among the eight compounds, compound 1 was the most active and selective against P. falciparum (IC50 = 0.98 µM; SI > 60). Six targets were identified in BraMMT that interact with compounds exhibiting a stronger binding energy than the crystallographic ligand: P. falciparum triophosphate phosphoglycolate complex (1LYX), P. falciparum reductase (2OK8), PfPK7 (2PML), P. falciparum glutaredoxin (4N0Z), PfATP6, and PfHT. Conclusions: The physicochemical properties of compound 1 were compatible with the set of criteria established by the Lipinski rule and demonstrated its potential as a drug prototype for antiplasmodial activity.

Docking, QM/MM, and molecular dynamics simulations of the hexose transporter from Plasmodium falciparum (PfHT).

Malaria is the most prevalent parasitic disease in the world. Currently, an effective vaccine for malaria does not exist, and chemotherapy must be used to treat the disease. Because of increasing resistance to current antimalarial drugs, new treatments must be developed. Among the many potential molecular targets, the hexose transporter of Plasmodium falciparum (PfHT) is particularly promising because it plays a vital role in glucose transport for the parasite. Thus, this study aims to determine the three-dimensional structure of PfHT and to describe the intermolecular interactions between active glycoside derivatives and PfHT. Such information should aid in the development of new antimalarial drugs. The receptor PfHT was constructed from primary sequences deposited in the SWISS MODEL database. Next, molecular docking simulations between O-(undec-10-en)-l-D-glucose and the constructed active site models were performed using Autodock Vina. The glycoside derivative-PfHT complexes were then refined using the hybrid QM/MM (PM3/ff03) method within the AMBER package. The models were then evaluated using Ramachandran plots, which indicated that 93.2% of the residues in the refined PfHT models (P5) were present in favorable regions. Furthermore, graphical plots using ANOLEA showed that the potential energies of interaction for atoms unbonded to P5 were negative. Finally, the O-(undec-10-en)-l-D-glucose-PfHT complex was evaluated using 20-ns Molecular Dynamics simulations with an ff03 force field. Docking and QM/MM studies revealed the amino acids essential for molecular recognition of and activity on glycosides. Inhibition of glucose transporters may prevent the development and metabolism of P. falciparum, so a description of the receptor's structure is a critical step towards rational drug design.

Dehydrobufotenin extracted from the Amazonian toad Rhinella marina (Anura: Bufonidae) as a prototype molecule for the development of antiplasmodial drugs

he resistance against antimalarial drugs represents a global challenge in the fight and control of malaria. The Brazilian biodiversity can be an important tool for research and development of new medicinal products. In this context, toxinology is a multidisciplinary approach on the development of new drugs, including the isolation, purification, and evaluation of the pharmacological activities of natural toxins. The present study aimed to evaluate the cytotoxicity, as well as the antimalarial activity in silico and in vitro of four compounds isolated from Rhinella marina venom as potential oral drug prototypes. Methods: Four compounds were challenged against 35 target proteins from P. falciparum and screened to evaluate their physicochemical properties using docking assay in Brazilian Malaria Molecular Targets (BraMMT) software and in silico assay in OCTOPUS® software. The in vitro antimalarial activity of the compounds against the 3D7 Plasmodium falciparum clones were assessed using the SYBR Green I based assay (IC50). For the cytotoxic tests, the LD50 was determined in human pulmonary fibroblast cell line using the [3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay. Results: All compounds presented a ligand-receptor interaction with ten Plasmodium falciparum-related protein targets, as well as antimalarial activity against chloroquine resistant strain (IC50 = 3.44 µM to 19.11 µM). Three of them (dehydrobufotenine, marinobufagin, and bufalin) showed adequate conditions for oral drug prototypes, with satisfactory prediction of absorption, permeability, and absence of toxicity. In the cell viability assay, only dehydrobufotenin was selective for the parasite. Conclusions: Dehydrobufotenin revealed to be a potential oral drug prototype presenting adequate antimalarial activity and absence of cytotoxicity, therefore should be subjected to further studies.(AU)

Brazilian malaria molecular targets (BraMMT): selected receptors for virtual high-throughput screening experiments

BACKGROUND Owing to increased spending on pharmaceuticals since 2010, discussions about rising costs for the development of new medical technologies have been focused on the pharmaceutical industry. Computational techniques have been developed to reduce costs associated with new drug development. Among these techniques, virtual high-throughput screening (vHTS) can contribute to the drug discovery process by providing tools to search for new drugs with the ability to bind a specific molecular target. OBJECTIVES In this context, Brazilian malaria molecular targets (BraMMT) was generated to execute vHTS experiments on selected molecular targets of Plasmodium falciparum. METHODS In this study, 35 molecular targets of P. falciparum were built and evaluated against known antimalarial compounds. FINDINGS As a result, it could predict the correct molecular target of market drugs, such as artemisinin. In addition, our findings suggested a new pharmacological mechanism for quinine, which includes inhibition of falcipain-II and a potential new antimalarial candidate, clioquinol. MAIN CONCLUSIONS The BraMMT is available to perform vHTS experiments using OCTOPUS or Raccoon software to improve the search for new antimalarial compounds. It can be retrieved from www.drugdiscovery.com.br or download of Supplementary data.

In vitro and in vivo antimalarial activity of the volatile oil of Cyperus articulatus (Cyperaceae)

Malaria is a disease of global tropical distribution, being endemic in more than 90 countries and responsible for about 212 million cases worldwide in 2016. To date, the strategies used to eradicate this disease have been ineffective, without specific preventive measures such as vaccines. Currently, the existing therapeutic arsenal is limited and has become ineffective against the expansion of artemisinin-resistant Plasmodium, demonstrating the need for studies that would allow the development of new compounds against this disease. In this context, we studied the volatile oil obtained from rhizomes of Cyperus articulatus (VOCA), a plant species commonly found in the Amazon region and popularly used as a therapeutic alternative for the treatment of malaria, in order to confirm its potential as an antimalarial agent by in vitro and in vivo assays. We cultured Plasmodium falciparum W2 (chloroquine-resistant) and 3D7 (chloroquine-sensitive) strains in erythrocytes and exposed them to VOCA at different concentrations in 96-well microplates. In vivo antimalarial activity was tested in BALB/c mice inoculated with approximately 106 erythrocytes infected with Plasmodium berghei. VOCA showed a high antimalarial potential against the two P. falciparum strains, with IC50 = 1.21 µg mL-1 for W2 and 2.30 µg mL-1 for 3D7. VOCA also significantly reduced the parasitemia and anemia induced by P. berghei in mice. Our results confirmed the antimalarial potential of the volatile oil of Cyperus articulatus. (AU)

Successful application of virtual screening and molecular dynamics simulations against antimalarial molecular targets

The main challenge in the control of malaria has been the emergence of drug-resistant parasites. The presence of drug-resistant Plasmodium sp. has raised the need for new antimalarial drugs. Molecular modelling techniques have been used as tools to develop new drugs. In this study, we employed virtual screening of a pyrazol derivative (Tx001) against four malaria targets: plasmepsin-IV, plasmepsin-II, falcipain-II, and PfATP6. The receiver operating characteristic curves and area under the curve (AUC) were established for each molecular target. The AUC values obtained for plasmepsin-IV, plasmepsin-II, and falcipain-II were 0.64, 0.92, and 0.94, respectively. All docking simulations were carried out using AutoDock Vina software. The ligand Tx001 exhibited a better interaction with PfATP6 than with the reference compound (-12.2 versus -6.8 Kcal/mol). The Tx001-PfATP6 complex was submitted to molecular dynamics simulations in vacuum implemented on an NAMD program. The ligand Tx001 docked at the same binding site as thapsigargin, which is a natural inhibitor of PfATP6. Compound TX001 was evaluated in vitro with a P. falciparum strain (W2) and a human cell line (WI-26VA4). Tx001 was discovered to be active against P. falciparum (IC50 = 8.2 µM) and inactive against WI-26VA4 (IC50 > 200 µM). Further ligand optimisation cycles generated new prospects for docking and biological assays.