Dihydrofolate Reductase-thymidylate Synthase Research Articles

Characterization, In Silico Antimalarial, Antiinflammatory, Antioxidant, and ADMET Assessment of Neonauclea excelsa Merr.

In our study, we identified the phytoconstituents and carried out antimalarial, anti-inflammatory, antioxidant, and ADMET assessments of Neonauclea excelsa. The phytochemicals were detected and quantified followed by identification via GC-MS. The antimalaria, anti-inflammatory, and antioxidant assessments were done by molecular docking (MD) and molecular dynamics simulation (MDS) while ADMET by ADMET predictions. Saponins (27.33% ±1.20) and terpenes (8.33% ±0.73) were detected while alkaloids, steroids, glycosides, and flavonoids were absent. Exactly 29 compounds were identified with squalene being the most abundant (32.41%). Compound II exhibited the lowest BA (-6.4 kcal/mol) and Ki (20.12 µM), interacting with dihydrofolate reductase-thymidylate synthase. IV exhibited the lowest respective BA and Ki interacting with Plasmodium falciparum hexose transporter protein 1 (-6.2 kcal/mol and 28.20 µM), cyclo-oxygenase-2 (-7.2 kcal/mol and 5.21 µM), and myeloperoxidase (-7.4 kcal/mol and 3.71 µM). Compound VII had the lowest respective BA and Ki interacting with inducible nitric oxide synthase (-8.0 kcal/mol and 1.35 µM), xanthine oxidase (-7.2 kcal/mol and 5.21 µM), and cytochrome p450 21A2 (-7.0 kcal/mol and 7.30 µM). The MDS showed various cluster mobilities and residue fluctuations up to 5.26, 2.96, 5.10, 3.51, 5.02, 4.65, and 6.18 Å for dihydrofolate reductase-thymidylate synthase, Plasmodium falciparum hexose transporter protein 1, inducible nitric oxide synthase (INOS), cyclo-oxygenase-2 (COX2), xanthine oxidase (XO), cytochrome p450 21A2, and myeloperoxidase, respectively. Additionally, these compounds demonstrated good pharmacological properties with minimal toxicity. Conclusively, the identified compounds might be significant contributors to the antimalarial, anti-inflammatory, and antioxidant activity of N. excelsa and are good sources of novel antimalarial, anti-inflammatory, and antioxidant drugs.

Antimalarial target vulnerability of the putative Plasmodium falciparum methionine synthase.

Plasmodium falciparum possesses a cobalamin-dependent methionine synthase (MS). MS is putatively encoded by the PF3D7_1233700 gene, which is orthologous and syntenic in Plasmodium. However, its vulnerability as an antimalarial target has not been assessed. We edited the PF3D7_1233700 and PF3D7_0417200 (dihydrofolate reductase-thymidylate synthase, DHFR-TS) genes and obtained transgenic P. falciparum parasites expressing epitope-tagged target proteins under the control of the glmS ribozyme. Conditional loss-of-function mutants were obtained by treating transgenic parasites with glucosamine. DHFR-TS, but not MS mutants showed a significant proliferation defect over 96 h, suggesting that P. falciparum MS is not a vulnerable antimalarial target.

Machine-Learning- and Structure-Based Virtual Screening for Selecting Cinnamic Acid Derivatives as Leishmania major DHFR-TS Inhibitors.

The critical enzyme dihydrofolate reductase-thymidylate synthase in Leishmania major (LmDHFR-TS) serves a dual-purpose role and is essential for DNA synthesis, a cornerstone of the parasite's reproductive processes. Consequently, the development of inhibitors against LmDHFR-TS is crucial for the creation of novel anti-Leishmania chemotherapies. In this study, we employed an in-house database containing 314 secondary metabolites derived from cinnamic acid that occurred in the Asteraceae family. We conducted a combined ligand/structure-based virtual screening to identify potential inhibitors against LmDHFR-TS. Through consensus analysis of both approaches, we identified three compounds, i.e., lithospermic acid (237), diarctigenin (306), and isolappaol A (308), that exhibited a high probability of being inhibitors according to both approaches and were consequently classified as promising hits. Subsequently, we expanded the binding mode examination of these compounds within the active site of the test enzyme through molecular dynamics simulations, revealing a high degree of structural stability and minimal fluctuations in its tertiary structure. The in silico predictions were then validated through in vitro assays to examine the inhibitory capacity of the top-ranked naturally occurring compounds against LmDHFR-TS recombinant protein. The test compounds effectively inhibited the enzyme with IC50 values ranging from 6.1 to 10.1 μM. In contrast, other common cinnamic acid derivatives (i.e., flavonoid glycosides) from the Asteraceae family, such as hesperidin, isovitexin 4'-O-glucoside, and rutin, exhibited low activity against this target. The selective index (SI) for all tested compounds was determined using HsDHFR with moderate inhibitory effect. Among these hits, lignans 306 and 308 demonstrated the highest selectivity, displaying superior SI values compared to methotrexate, the reference inhibitor of DHFR-TS. Therefore, continued research into the anti-leishmanial potential of these C6C3-hybrid butyrolactone lignans may offer a brighter outlook for combating this neglected tropical disease.

In Silico and In Vitro Search for Dual Inhibitors of the Trypanosoma brucei and Leishmania major Pteridine Reductase 1 and Dihydrofolate Reductase.

The parasites Trypanosoma brucei (Tb) and Leishmania major (Lm) cause the tropical diseases sleeping sickness, nagana, and cutaneous leishmaniasis. Every year, millions of humans, as well as animals, living in tropical to subtropical climates fall victim to these illnesses' health threats. The parasites' frequent drug resistance and widely spread natural reservoirs heavily impede disease prevention and treatment. Due to pteridine auxotrophy, trypanosomatid parasites have developed a peculiar enzyme system consisting of dihydrofolate reductase-thymidylate synthase (DHFR-TS) and pteridine reductase 1 (PTR1) to support cell survival. Extending our previous studies, we conducted a comparative study of the T. brucei (TbDHFR, TbPTR1) and L. major (LmDHFR, LmPTR1) enzymes to identify lead structures with a dual inhibitory effect. A pharmacophore-based in silico screening of three natural product databases (approximately 4880 compounds) was performed to preselect possible inhibitors. Building on the in silico results, the inhibitory potential of promising compounds was verified in vitro against the recombinant DHFR and PTR1 of both parasites using spectrophotometric enzyme assays. Twelve compounds were identified as dual inhibitors against the Tb enzymes (0.2 μM < IC50 < 85.1 μM) and ten against the respective Lm enzymes (0.6 μM < IC50 < 84.5 μM). These highly promising results may represent the starting point for the future development of new leads and drugs utilizing the trypanosomatid pteridine metabolism as a target.

Antimalarial and Antileishmanial Flavonoids from Calendula officinalis Flowers

Calendula officinalis L. (Asteraceae), commonly known as English or pot marigold, is an herbaceous plant with edible flowers. In this study, UPLC-ESI-MS/MS analysis was used for tentative identification of compounds in marigold flower methanol extract (MFE). In addition, RP-HPLC-DAD analysis was used to quantify the flavonoids hesperidin and rutin in MFE. The antileishmanial potentials of the crude extract and compounds were evaluated against Leishmania major promastigotes and amastigotes. Further, in vivo 4-day antimalarial testing of the extract and compounds was carried out at doses of 25 mg kg−1 per day using mice infected with ANKA strain of Plasmodium berghei, following standard procedure. Molecular docking studies were carried out to assess the binding mode of flavonoids against the vital targets of L. major, including pteridine reductase 1 and farnesyl diphosphate synthase enzymes. The in silico antimalarial potentials of flavonoids were evaluated against wild-type Plasmodium falciparum dihydrofolate reductase-thymidylate synthase and phosphoethanolamine methyltransferase enzymes. Twenty compounds were tentatively identified by UPLC-ESI-MS/MS analysis of MFE, of which, seven flavonoids, six saponins, three phenolic acids, three fatty acids, and a triterpene glycoside were identified. MFE phytochemical analysis revealed that hesperidin content was 36.17 mg g−1 extract, that is, 9.9-fold their content of rutin (3.65 mg g−1 extract). The method was validated to ensure reproducibility of the results. The tested samples exhibited antileishmanial potentials against L. major promastigotes, with IC50 values of 98.62, 118.86, and 104.74 ng µL−1 for hesperidin, rutin, and MFE, respectively. Likewise, hesperidin showed inhibitory potentials against L. major amastigote with an IC50 value of 108.44 ± 11.2 µM, as compared to miltefosine. The mean survival time, parasitemia, and suppression percentages showed similar results for the three samples against ANKA strain of P. berghei. The docking studies showed good binding affinities of rutin and hesperidin with numerous H-bonding and van der Waals interactions. Marigold flowers are nutraceuticals, presenting important sources of bioactive flavonoids with potential against neglected tropical diseases.

In vitro and in silico anti-malarial activity and cytotoxicity of n-hexyl 1-O-rutinoside (a glycoside) isolated from Annickia polycarpa (DC.) Setten and Maas ex I.M. Turner (Annonaceae)

Ethnopharmacological relevanceAnnickia polycarpa leaf is an effective anti-malarial agent. However, its chemical constituents have not been isolated and assayed against any pathogen. Aim of the studyTo isolate and characterize anti-malarial compound(s) from the leaf of A. polycarpa. Materials and methodsBioassay-guided fractionation was employed to isolated the compound (AL1) from the chloroform fraction (ALCF) of the basified ethanol extract of A. polycarpa leaf (ALE). AL1 was characterized by LC-MS, 1D and 2D NMR spectroscopic analysis. Anti-malarial activity was evaluated against drug resistance Dd2 and drug sensitive 3D7 Plasmodium falciparum strains using the SYBR green assay. Cytotoxicity and mechanistic studies were determined using tetrazolium-based colorimetric assay and molecular docking respectively. ResultsAL1 was characterized as n-hexyl 1-O-rutinoside. The IC50 values of ALE and ALCF against 3D7 and Dd2 P. falciparum strains ranges from 3.441 (0.3389) - 4.255 (0.2246) μg/mL. The IC50s obtained for n-hexyl 1-O-rutinoside and Artesunate (standard drug) were 7.71 (0.5473) and 0.001 (0.00008) nM against the 3D7 parasite strain respectively. Also, the efficacy of n-hexyl 1-O-rutinoside increased by 24.40% against the chloroquine resistance Dd2 P. falciparum strain whiles that of Artesunate decreased by 98.96%. Furthermore, ALE, ALCF and n-hexyl 1-O-rutinoside were weakly cytotoxic to human RBCs with high selectivity indices. N-hexyl 1-O-rutinoside inhibits P. falciparum chloroquine resistance transporter (PfCRT) and dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) better than chloroquine and pyrimethamine respectively. But, produced similar inhibition of P. falciparum 2-trans-enoyl -ACP-reductase (PfERN) as triclosan. ConclusionThese results show that A. polycarpa leaf and n-hexyl 1-O-rutinoside possessed profound anti-malarial activity and are not cytotoxic. N-hexyl 1-O-rutinoside could therefore, be developed into a new anti-malarial medicine. This is the first study to report the anti-malarial activity of n-hexyl 1-O-rutinoside and its isolation from the genus Annickia.

Revelation of potential drug targets of luteolin in Plasmodium falciparum through multi-target molecular dynamics simulation studies

In-silico techniques offer a fast, accurate, reliable, and economical approach to studying the molecular interactions between compounds and proteins. In this study, our main aim is to use in-silico techniques as a rational approach for the prediction of the molecular drug targets for luteolin against Plasmodium falciparum. Multi-target molecular docking, 100 nanoseconds (ns) molecular dynamics (MD) simulations, and Molecular Mechanics-Generalized Born Surface Area (MM-GBSA) binding free energy calculations were carried out for luteolin against dihydrofolate reductase thymidylate synthase (PfDHFR-TS), dihydroorotate dehydrogenase (PfDHODH), and falcipain-2. The native ligands of each protein were used as a reference to evaluate the performance of luteolin. Luteolin outperformed the native ligands of all proteins at molecular docking and MD simulations studies. However, in the MM-GBSA calculations, luteolin outperformed the native ligand of only PfDHFR-TS but not PfDHODH and falcipain-2. Among the studied proteins, the in-silico approach predicted PfDHFR-TS as the most favorable drug target for luteolin. Communicated by Ramaswamy H. Sarma

An In-Silico Investigation on the Molecular Interactions between Ellagic Acid and PfDHFR-TS

Ellagic acid (EA) is an antiplasmodial polyphenol with reported in-vitro activity against Plasmodium falciparum. Studies have reported that EA acts in the late erythrocytic stages of P. falciparum (Pf) when DNA synthesis is taking place. Pf dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) is an important enzyme for DNA synthesis as its inhibition can kill the parasite. As there is no reported study on the molecular interactions between EA and PfDHFR-TS, we aim to study the molecular interactions between EA and PfDHFR-TS (PDB ID: 3DGA) through molecular docking, molecular dynamics (MD) simulations, binding free energy (MM-GBSA) calculations, and density functional theory (DFT) studies. Site-specific and blind docking revealed that EA has a high binding affinity for the active site of PfDHFR-TS. EA formed hydrogen bonds with multiple active site residues. MD simulations for 100 ns revealed that the PfDHFR-TS-EA complex was stable. The average binding free energy of the PfDHFR-TS-EA complex throughout the 100 ns MD simulations was −39.84 kcal/mol. The energy difference (ΔE = 0.04089 eV) obtained from DFT studies indicates the electrical stability and reactivity of EA at the active site of PfDHFR-TS. We conclude that the antiplasmodial activity of EA might be attributed to its ability to potentially bind with PfDHFR-TS.

Palladium-catalyzed facile synthesis of imidazo[1,2-a]pyridine-flavone hybrids and evaluation of their antiplasmodial activity

An efficient cross-coupling reaction between imidazo[1,2-a]pyridine derivatives and 6-bromoflavones has been well established. This reaction proceeds through a Palladium-catalyzed cross-coupling reaction to provide imidazo[1,2-a]pyridine-flavone hybrids in good to excellent yield. Short reaction time, high yield, and wide substrate scope are the major advantages of this method. Using SYBR Green I assay, these hybrid molecules were examined for anti-plasmodial activity against Chloroquine-sensitive 3D7 and Chloroquine-resistant K1 strains of Plasmodium falciparum. The compounds 9o {IC50s (µM) 1.983D7, 1.98K1} and 9p {IC50s (µM) 1.923D7, 5.45K1} were found to be the most potent anti-plasmodial compounds in the series. Also, all these compounds were found to be non-cytotoxic towards Vero cells with their CC50s > 100 µM. We have conducted microscopic examination experiments on compounds 9o and 9p, which resulted in a drastic impact on parasite growth of the malaria parasite. The interaction of these two potent hybrids was also examined in the binding site of wild-type Pf-DHFR-TS (Plasmodium falciparum dihydrofolate reductase-thymidylate synthase) using molecular docking studies. The computational ADME studies of the hybrid compounds confirmed their significant physicochemical, pharmacokinetic, and drug-likeness properties confirming these hybrids as a new oral antimalarial agent. As a result, these new hybrid compounds could be valuable in the creation of future antimalarial drugs.

Delving in folate metabolism in the parasite Leishmania major through a chemogenomic screen and methotrexate selection.

Most of our understanding of folate metabolism in the parasite Leishmania is derived from studies of resistance to the antifolate methotrexate (MTX). A chemical mutagenesis screen of L. major Friedlin and selection for resistance to MTX led to twenty mutants with a 2- to 400-fold decrease in MTX susceptibility in comparison to wild-type cells. The genome sequence of the twenty mutants highlighted recurrent mutations (SNPs, gene deletion) in genes known to be involved in folate metabolism but also in novel genes. The most frequent events occurred at the level of the locus coding for the folate transporter FT1 and included gene deletion and gene conversion events, as well as single nucleotide changes. The role of some of these FT1 point mutations in MTX resistance was validated by gene editing. The gene DHFR-TS coding for the dihydrofolate reductase-thymidylate synthase was the second locus with the most mutations and gene editing confirmed a role in resistance for some of these. The pteridine reductase gene PTR1 was mutated in two mutants. The episomal overexpression of the mutated versions of this gene, but also of DHFR-TS, led to parasites several fold more resistant to MTX than those overexpressing the wild-type versions. Genes with no known link with folate metabolism and coding for a L-galactolactone oxidase or for a methyltransferase were mutated in specific mutants. Overexpression of the wild-type versions of these genes in the appropriate mutants reverted their resistance. Our Mut-seq approach provided a holistic view and a long list of candidate genes potentially involved in folate and antifolate metabolism in Leishmania.

Screening Carica Papaya Compounds as an Antimalarial Agent: In Silico Study

Malaria is a highly prevalent infectious disease caused by the Plasmodium parasite transmitted through Anopheles mosquitoes, which poses a significant public health challenge worldwide, including in Indonesia. Therefore, a study was conducted to identify potential drug compounds from the Carica papaya plant that could inhibit various antimalarial proteins or receptors, such as Plasmodium falciparum DXR reductase complex with fosmidomycin, Plasmepsin V Plasmodium vivax, P. falciparum dihydroorotate dehydrogenase, P. falciparum hexose transporter, P. falciparum protein kinase 5, and P. falciparum dihydrofolate reductase-thymidylate synthase. Theresearchers used the Pyrx application to dock the C. papaya compounds with the targeted antimalarial proteins to determine the binding affinity values. Additionally, they used the Yasara dynamics application to conduct molecular dynamics simulation to ensure the stability of the bonds formed between the ligands and proteins. The results showed that 14 compounds found in C. papaya, particularly flavonoids and terpenoids, had the potential to inhibit the six antimalarial proteins with the lowest binding affinity values. Furthermore, the molecular dynamics simulation on 6M20 and 1V0P proteins indicated that the compounds effectively inhibited Plasmodium proteins, as they had an RMSD value below 2.5 Angstrom. The study suggests that C. papaya could be a potential source of antimalarial compounds, which could be developed into new drugs to combat this disease.&nbsp

Homology modeling, docking, and ADMET studies of benzoheterocyclic 4-aminoquinolines analogs as inhibitors of Plasmodiumfalciparum

ObjectivesThe ongoing fight against endemic diseases is necessary due to the growing resistance of malarial parasites to widely accessible medications. Thus, there has been an ongoing search for antimalarial medications with improved efficacy. The goal of this study was to develop derivatives of benzoheterocyclic 4-aminoquinolines with enhanced activities and better binding affinities than the original compounds. MethodsThirty-four derivatives of benzoheterocyclic 4-aminoquinolines were docked (using a model of dihydrofolate reductase-thymidylate synthase [DRTS] protein) with Molegro software to identify the compound with the minimum docking score as a design template. The generated quantitative structure–activity model was employed to estimate the activity of the designed derivatives. The derivatives were also docked to determine the most stable derivatives. Furthermore, the designed derivatives were tested for their drug-likeness and pharmacokinetic properties using SwissADME software and pkCSM web application, respectively. ResultsCompound H-014, (N-(7-chloroquinolin-4-yl)-2-(4-methylpiperazin-1-yl)-1,3-benzoxazol-5-amine) with the lowest re-rank score of −115.423 was employed as the design template. Then 10 derivatives were further designed by substituting –OH, –OCH3, –CHO, –F, and -Cl groups at various positions of the template. We found that the designed derivatives had improved activities compared to the template. The docking scores of the designed derivatives were lower than those of the original derivatives. Derivative h-06 (7-methoxy-4-((2-(4-methylpiperazin-1-yl)benzo[d]oxazol-5-yl)amino)quinolin-6-ol) with four hydrogen bonds was identified as the most stable due to its lowest re-rank score (−163.607). While all of the designed derivatives satisfied both the Lipinski and Verber rules, some derivatives such as h-10 (cytochrome P450 1A2 [CYP1A2]); h-05, h-08, h-09, and h-10 [CYP2C19]; and h-03, h-07, h-08, and h-10 [renal organic cation transporter 2 substrate]) showed poor absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties. ConclusionTen derivatives of benzoheterocyclic 4-aminoquinolines were designed with improved efficacies. Derivatives that follow Lipinski and Verber rules and are mostly non-toxic and non-sensitive to the skin can be utilized in the development of effective antimalarial medications.

Antimalarial potential, LC–MS secondary metabolite profiling and computational studies of Zingiber officinale

Malaria is among the top-ranked parasitic diseases that pose a threat to the existence of the human race. This study evaluated the antimalarial effect of the rhizome of Zingiber officinale in infected mice, performed secondary metabolite profiling and detailed computational antimalarial evaluation through molecular docking, molecular dynamics (MD) simulation and density functional theory methods. The antimalarial potential of Z. officinale was performed using the in vivo chemosuppressive model; secondary metabolite profiling was carried out using liquid chromatography–mass spectrometry (LC–MS). Molecular docking was performed with Autodock Vina while the MD simulation was performed with Schrodinger desmond suite for 100 ns and DFT calculations with B3LYP (6-31G) basis set. The extract showed 64% parasitaemia suppression, with a dose-dependent increase in activity up to 200 mg/kg. The chemical profiling of the extract tentatively identified eight phytochemicals. The molecular docking studies with plasmepsin II and Plasmodium falciparum dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) identified gingerenone A as the hit molecule, and MMGBSA values corroborate the binding energies obtained. The electronic parameters of gingerenone A revealed its significant antimalarial potential. The antimalarial activity elicited by the extract of Z. officinale and the bioactive chemical constituent supports its usage in ethnomedicine. Communicated by Ramaswamy H. Sarma

Kaurane-Type Diterpenoids as Potential Inhibitors of Dihydrofolate Reductase-Thymidylate Synthase in New World Leishmania Species.

The bifunctional enzyme Dihydrofolate reductase-thymidylate synthase (DHFR-TS) plays a crucial role in the survival of the Leishmania parasite, as folates are essential cofactors for purine and pyrimidine nucleotide biosynthesis. However, DHFR inhibitors are largely ineffective in controlling trypanosomatid infections, largely due to the presence of Pteridine reductase 1 (PTR1). Therefore, the search for structures with dual inhibitory activity against PTR1/DHFR-TS is crucial in the development of new anti-Leishmania chemotherapies. In this research, using the Leishmania major DHFR-TS recombinant protein, enzymatic inhibitory assays were performed on four kauranes and two derivatives that had been previously tested against LmPTR1. The structure 302 (6.3 µM) and its derivative 302a (4.5 µM) showed the lowest IC50 values among the evaluated molecules. To evaluate the mechanism of action of these structures, molecular docking calculations and molecular dynamics simulations were performed using a DHFR-TS hybrid model. Results showed that hydrogen bond interactions are critical for the inhibitory activity against LmDHFR-TS, as well as the presence of the p-hydroxyl group of the phenylpropanoid moiety of 302a. Finally, additional computational studies were performed on DHFR-TS structures from Leishmania species that cause cutaneous and mucocutaneous leishmaniasis in the New World (L. braziliensis, L. panamensis, and L. amazonensis) to explore the targeting potential of these kauranes in these species. It was demonstrated that structures 302 and 302a are multi-Leishmania species compounds with dual DHFR-TS/PTR1 inhibitory activity.

Screening for antifolate and artemisinin resistance in Plasmodium falciparum clinical isolates from three hospitals of Eritrea

Background: Antimalarial drug resistance is a major challenge hampering malaria control and elimination. Plasmodium falciparum, the leading causative parasite species, has developed resistance to basically all antimalarials. Continued surveillance of drug resistance using genetic markers provides important molecular data for treatment policies. This study sought to verify the genetic mechanism of resistance to sulfadoxine-pyrimethamine and assess the occurrence of point mutations associated with artemisinin resistance in P. falciparum clinical isolates from Eritrea. Methods: Nineteen dried blood spot samples were collected from patients visiting Adi Quala, Keren and Gash Barka Hospitals, Eritrea. The patients were followed up after receiving treatment with first line artesunate-amodiaquine. Nested polymerase chain reaction and Sanger sequencing techniques were employed to genotype point mutations in the P. falciparum bifunctional dihydrofolate reductase-thymidylate synthase (Pfdhfr, PF3D7_0417200), dihydropteorate synthase (Pfdhps, PF3D7_0810800) and kelch 13 (PfK13, PF3D7_1343700) genes. Results: Eight of nineteen (42%) of the dried blood spot samples were successful for PCR-amplification. Data analyses of the PCR-positive isolates revealed the following point mutations: Pfdhfr N51I in four isolates, C59R in one isolate, S108N in four isolates, a rare non-synonymous substitution V45A in four isolates and Pfdhps K540E in four isolates. No PfK13 point mutations were reported. Conclusions: Pfdhfr C59R and Pfdhps K540E point mutations are reliable markers for the sulfadoxine-pyrimethamine quintuple mutant haplotype combination. These findings highlight first reports in Eritrea, which verify the underlying genetic mechanism of antifolate resistance. Continuous monitoring of the PfK13 marker is recommended.

Evaluation of Zamia floridana A. DC. Leaves and Its Isolated Secondary Metabolites as Natural Anti-Toxoplasma and Anti-Cancer Agents Using In Vitro and In Silico Studies.

Toxoplasmosis and cancer are life-threatening diseases with worldwide distribution. However, currently used chemosynthetic treatments are not devoid of their own intrinsic problems. Natural metabolites are gaining attention due to their lower side effects. In this study, we investigated for the first time Zamia floridana leaves extract and its different fractions for their toxoplasmocidal activity, using Virulent RH&amp;nbsp;Toxoplasma gondii, and cytotoxic activity against MCF-7 and HCT-116 cancer cell lines using MTT assay. The n-butanol fraction was the most potent fraction against T. gondii with an EC50 of 7.16 ± 0.4 µg/mL compared to cotrimoxazole (4.18 ± 0.3 µg/mL). In addition, the n-BuOH fraction showed a significant cytotoxicity against MCF-7 and HCT-116 with IC50 of 12.33 ± 1.1 and 17.88 ± 1.4 µg/mL, respectively, compared to doxorubicin (4.17 ± 0.2 and 5.23 ± 0.3 µg/mL, respectively), with higher safety index against normal cell line (WISH). Therefore, the n-BuOH fraction was investigated for its phytochemicals using extensive chromatographic techniques, which led to the isolation of six compounds that were fully characterized using different spectroscopic techniques. Three biflavonoids (1, 2 and 4) in addition to two phenolic acid derivatives (3 and 5) and a flavonoid glycoside (6) were isolated. Compounds (1, 3, 5 and 6) were reported for the first time from Z. floridana. In silico docking studies for toxoplasmocidal and cytotoxic effects of these compounds revealed that compounds (1, 2, 4 and 6) have promising inhibition potential of either thymidylate synthase-dihydrofolate reductase (TS-DHFR) or cyclin dependent kinase 2 (CDK2) target proteins. This study is considered the first report of chemical and biological investigation of Z. floridana leaves.

Quantitative Structure-Activity Relationship, Structure-based Design, and ADMET studies of pyrimethamine and cycloguanil analogs inhibitors of Plasmodium falciparum dihydrofolate reductase-thymidylate synthase (PfDHFR-TS).

Quantitative Structure-Activity Relationship, Structure-based Design, and ADMET studies of pyrimethamine and cycloguanil analogs inhibitors of Plasmodium falciparum dihydrofolate reductase-thymidylate synthase (PfDHFR-TS).

Substituted 3-styryl-2-pyrazoline Derivatives as an Antimalaria: Synthesis, in vitro Assay, Molecular Docking, Druglikeness Analysis and Admet Prediction

The synthesis, in vitro antimalarial assay, molecular docking, drug-likeness analysis, and ADMET prediction of substituted 3-styryl-2-pyrazoline derivatives as antimalaria have been conducted. The synthesis of N-phenyl (1a‒3a) and N-acetyl-substituted (1b‒3b) 3-styryl-2-pyrazolines was carried out using dibenzalacetone derivatives and hydrazine hydrate or phenylhydrazine. An in vitro antimalarial assay was conducted against the chloroquine-sensitive Plasmodium falciparum 3D7 strain, while molecular docking was performed toward the crystal protein of Plasmodium falciparum dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) (PDB ID: 1J3I). Furthermore, the prediction of drug-like properties was determined by assessing Lipinski’s rules, and the pharmacokinetic parameters were also studied in-silico, including absorption, distribution, metabolism, excretion, and toxicity (ADMET). The in vitro assay showed that 3a (IC50 0.101 µM) has excellent antimalarial activity, followed by 2a (0.177 µM), and 1b (0.258 µM). Molecular docking has supported the in vitro assay by showing the lowest CDOCKER energy for 3a (‒56.316 kcal/mol), then 2a (‒51.2603 kcal/mol), and 1b (‒48.8774 kcal/mol). The drug-like properties showed that all of the prepared compounds were acceptable based on Lipinski’s rules and predicted to be potentially orally bioavailable. The ADMET analysis provided information that 3a and 2a could be proposed as the best lead antimalarial drugs with further modification to reduce the lipophilicity and toxicity properties.

The Broad-Spectrum Antitrypanosomal Inhibitory Efficiency of the Antimetabolite/Anticancer Drug Raltitrexed

Raltitrexed is a classical antifolate drug with antimetabolite and anticancer properties. In this research, we provide its detailed antitrypanosomal inhibition against six Trypanosoma species and investigate its potential mode of action. Molecular dynamics (MD) simulations and in silico analyses were used to track the binding strength and stability. Raltitrexed showed broad-spectrum trypanocidal actions against Trypanosoma brucei brucei GUTat3.1, T. b. rhodesiense IL1501, T. b. gambiense IL1922, T. evansi Tansui, T. equiperdum IVM-t1 and T. congolense IL3000. The estimated IC50 was found to be in the range of 5.18–24.13 µg/mL, indicating inhibition of Trypanosoma in the low micromolar range. Although the co-crystallized ligand had robust hydrogen bonding and lipophilic characteristics, its docking score was only −4.6 compared to raltitrexed’s −7.78, indicating strong binding with T. brucei dihydrofolate reductase-thymidylate synthase (TbDHFR-TS). MD simulations support the strong binding of raltitrexed with TbDHFR-TS evidenced by low root mean square deviation (RMSD), low residues fluctuations, a tight radius of gyration (ROG) and an average of 3.38 ± 1.3 hydrogen bonds during 50 ns MD simulation. The prospective extended spectrum of raltitrexed against Trypanosoma species grants further research for the synthesis of raltitrexed derivatives and repurposing against other protozoa.

Single- and duplex TaqMan-quantitative PCR for determining the copy numbers of integrated selection markers during site-specific mutagenesis in Toxoplasma gondii by CRISPR-Cas9.

Herein, we developed a single and a duplex TaqMan quantitative PCR (qPCR) for absolute quantification of copy numbers of integrated dihydrofolate reductase-thymidylate synthase (mdhfr-ts) drug selectable marker for pyrimethamine resistance in Toxoplasma gondii knockouts (KOs). The single TaqMan qPCR amplifies a 174 bp DNA fragment of the inserted mdhfr-ts and of the wild-type (WT) dhfr-ts (wtdhfr-ts) which is present as single copy gene in Toxoplasma and encodes a sensitive enzyme to pyrimethamine. Thus, the copy number of the dhfr-ts fragment in a given DNA quantity from KO parasites with a single site-specific integration should be twice the number of dhfr-ts copies recorded in the same DNA quantity from WT parasites. The duplex TaqMan qPCR allows simultaneous amplification of the 174 bp dhfr-ts fragment and the T. gondii 529-bp repeat element. Accordingly, for a WT DNA sample, the determined number of tachyzoites given by dhfr-ts amplification is equal to the number of tachyzoites determined by amplification of the Toxoplasma 529-bp, resulting thus in a ratio of 1. However, for a KO clone having a single site-specific integration of mdhfr-ts, the calculated ratio is 2. We then applied both approaches to test T. gondii RH mutants in which the major surface antigen (SAG1) was disrupted through insertion of mdhfr-ts using CRISPR-Cas9. Results from both assays were in correlation showing a high accuracy in detecting KOs with multiple integrated mdhfr-ts. Southern blot analyses using BsaBI and DraIII confirmed qPCRs results. Both TaqMan qPCRs are needed for reliable diagnostic of T. gondii KOs following CRISPR-Cas9-mediated mutagenesis, particularly with respect to off-target effects resulting from multiple insertions of mdhfr-ts. The principle of the duplex TaqMan qPCR is applicable for other selectable markers in Toxoplasma. TaqMan qPCR tools may contribute to more frequent use of WT Toxoplasma strains during functional genomics.