Dd2 Strains Research Articles

“Hydroethanol extract and triterpenoids of Senegalia ataxacantha show antiplasmodial activity and the compounds are predicted to inhibit parasite lactate dehydrogenase (pfLDH) as indicated by molecular docking studies”

Malaria claims over 600,000 deaths annually with a disproportionately high burden in the WHO African Region. The development of parasite resistance has warranted the search for novel anti-plasmodial drug candidates. This research aimed at validating the efficacy of Senegalia ataxacantha and tracking down its bioactive constituents. In vivo antiplasmodial activity of the extract was assessed using suppressive and curative protocols. Yeast-induced pyrexia was employed to evaluate the antipyretic activity of the extract. In vitro anti-plasmodial activity of isolated compounds was done using SYBR green I fluorescence assay on chloroquine sensitive (3D7) and resistant (Dd2) strains of P falciparum. In silico pharmacokinetic and interactions with parasites lactate dehydrogenase predictions of isolated compounds was conducted through molecular docking studies. Ethanol (70 %) extract of the plant showed in vitro and in vivo anti-plasmodial effect. The extract demonstrated significant (p < 0.05) dose-dependent suppression of 63.39 % and 63.32 % respectively at the highest dose (300 mg kg-1). Artesunate (4 mg kg-1/day) had considerably better curative potential (85.25%). The compounds showed in vitro anti-plasmodial activity in the order lupeol> friedelin/ friedelinol mixture>friedelin>β-sitosterol based on IC50 measurement. Friedelinol and lupeol exhibited higher binding affinities with pfLDH compared to Chloroquine. The extract and acetaminophen (positve control) showed significant (p < 0.05) reduction in rectal temperature compared to the control group. In silico studies of the compounds revealed moderate interactions with some cytochrome P450 metabolizing enzymes. S. ataxacantha stem extract shows anti-plasmodial and antipyretic activities which may be due to its pentacyclic triterpenoid constituents inhibiting pfLDH.

Exploring the Antimalarial Potential of Entandrophragma Utile and Melochia Umbellata Extracts.

Resistance remains the fundamental problem with antiplasmodial treatments. The study investigated the antiplasmodial, cytotoxic, and antioxidant properties of two Cameroonian medicinal plants, Entandrophragma utile and Melochia umbellata. Antimalarial activity against Plasmodium falciparum strains 3D7 and Dd2 was assessed using the SYBR Green I assay. Cytotoxicity was assessed against Raw and Vero cells using the resazurin assay, and against red blood cells using a hemoglobin release quantification assay. Antioxidant potential was determined using DPPH (2, 2-diphenyl-1-picrylhydrazine), ABTS (2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), and FRAP (ferric-reducing antioxidant power) assays. The most bioactive extract was further analyzed using ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) to determine its phytochemical composition. Extracts from E. utile exhibited moderate anti-malarial activity against Plasmodium falciparum (IC50 =32.81-100 μg/mL), while M. umbellata leaf extract (MULAE) showed strong activity (IC50 =11.62 and 11.91 μg/mL). All extracts demonstrated antioxidant activity (9.22 to 135.8 μg/mL), were selective for Raw and Vero cells, and were not toxic to red blood cells. UHPLC-MS analysis annotated potential pyrimidones, phenolic compounds, and terpenoids in MULAE. MULAE exhibited better antiplasmodial activity, suggesting the presence of unique bioactive compounds. Further research, including in vivo investigations, is needed to develop safe and effective antiplasmodial therapies.

Application of a new highly multiplexed amplicon sequencing tool to evaluate Plasmodium falciparum antimalarial resistance and relatedness in individual and pooled samples from Dschang, Cameroon.

Resistance to antimalarial drugs remains a major obstacle to malaria elimination. Multiplexed, targeted amplicon sequencing is being adopted for surveilling resistance and dissecting the genetics of complex malaria infections. Moreover, genotyping of parasites and detection of molecular markers drug resistance in resource-limited regions requires open-source protocols for processing samples, using accessible reagents, and rapid methods for processing numerous samples including pooled sequencing. P lasmodium f alciparum Streamlined Multiplex Antimalarial Resistance and Relatedness Testing (Pf-SMARRT) is a PCR-based amplicon panel consisting of 15 amplicons targeting antimalarial resistance mutations and 9 amplicons targeting hypervariable regions. This assay uses oligonucleotide primers in two pools and a non-proprietary library and barcoding approach. We evaluated Pf-SMARRT using control mocked dried blood spots (DBS) at varying levels of parasitemia and a mixture of 3D7 and Dd2 strains at known frequencies, showing the ability to genotype at low parasite density and recall within-sample allele frequencies. We then piloted Pf-SMARRT to genotype 100 parasite isolates collected from uncomplicated malaria cases at three health facilities in Dschang, Western Cameroon. Antimalarial resistance genotyping showed high levels of sulfadoxine-pyrimethamine resistance mutations, including 31% prevalence of the DHPS A613S mutation. No K13 candidate or validated artemisinin partial resistance mutations were detected, but one low-level non-synonymous change was observed. Pf-SMARRT's hypervariable targets, used to assess complexity of infections and parasite diversity and relatedness, showed similar levels and patterns compared to molecular inversion probe (MIP) sequencing. While there was strong concordance of antimalarial resistance mutations between individual samples and pools, low-frequency variants in the pooled samples were often missed. Overall, Pf-SMARRT is a robust tool for assessing parasite relatedness and antimalarial drug resistance markers from both individual and pooled samples. Control samples support that accurate genotyping as low as 1 parasite per microliter is routinely possible.

In vitro antiplasmodial and anticancer analyses of endophytic fungal extracts isolated from selected Nigerian medicinal plants

Ethnomedicinal plants are thought to have better prospects of harboring endophytes that produce natural products with pharmacological activities. This study aimed to investigate the antiplasmodial and anticancer properties of secondary metabolites of endophytic fungi from three medicinal plants. The endophytic fungi included Lasiodiplodia theobromae isolated from Cola acuminata, Curvularia lunata Bv4 isolated from Bambusa vulgaris, and Curvularia lunata Eg7 isolated from Elaeis guineensis. The identification of the fungi was based on the internal transcribed spacer (ITS-rDNA) sequence. The fungi were subjected to solid-state fermentation and the secondary metabolites were extracted with ethyl acetate. In vitro antiplasmodial screening of extracts was performed using the SYBR green I-based fluorescence assay on the chloroquine-resistant Plasmodium falciparum strain DD2. The cytotoxicity of the extracts on human red blood cells and Jurkat (leukemia) cells was assessed using the tetrazolium-based colorimetric MTT assay. Gas chromatography-mass spectrometry (GC–MS) analysis was used to identify the constituents of the fungal extracts. The extract of L. theobromae showed the best antiplasmodial activity against chloroquine-resistant P. falciparum (IC50 = 5.4 µg/mL) and was not harmful to erythrocytes (CC50 > 100 µg/mL). All three fungal extracts showed a weak cytotoxic effect against Jukart cell lines (CC50 > 100 µg/mL). GC–MS analysis of the three endophytic fungal extracts revealed the presence of forty major bioactive compounds, including: oxalic acid, isobutyl nonyl ester, 2,4-di-tert-butylphenol, and hexadecanoic acid, among others. The endophytic fungi from the medicinal plants in this study were promising sources of bioactive compounds that could be further evaluated as novel drugs for the treatment of malaria caused by P. falciparum-resistant strains.

In vitro, in vivo and in silico antiplasmodial profiling of the aqueous extract of Hibiscus asper HOOK F. Leaf (Malvaceae)

Ethnopharmacological relevancePlasmodium resistance to antimalarial drugs raises the urgent need to seek for alternative treatments. Aqueous extract of Hibiscus asper leaves is currently used in malaria management but remains less documented.Aim of the study: The study aims to evaluate antimalarial effects of the aqueous extract of Hibiscus asper. UHPLC/MS, was used to identify some likely compounds present in the plant that were thereafter docked to some malaria parasite proteins. Study designIn vitro anti-plasmodium and antioxidant, UHPLC/Ms analysis, in vivo antimalarial of the plant extract, and in silico molecular docking prediction of some identified compounds were performed to investigate the pharmacological effects of H. asper. Material and methodsThe in vitro antiplasmodial activity of the extract was carried out on Plasmodium falciparum strains using SYBR-green dye; then, the curative antimalarial activity was conducted on Plasmodium berghei NK65-infected male Wistar rats. The UHPLC/MS analysis was used to identify plant compounds, followed by interactions (docking affinity) between some compounds and parasitic enzymes such as P. falciparum purine nucleoside phosphorylase (2BSX) and 6-phosphogluconate dehydrogenase (6FQY) to explore potential mechanisms of action at the molecular level. ResultsNo hemolysis effect of the extract was observed at concentrations up to 100 mg/mL. In vitro test of the aqueous leaves extract of H. asper showed inhibitory activity against P. falciparum Dd2 and 3D7 strains with IC50 values of 19.75 and 21.97 μg/mL, respectively. The curative antimalarial test of the H. asper extract in infected rats exhibited significant inhibition of the parasite growth (p < 0.001) with inhibition percentage of 95.11%, 97.68% and 95.59% at all the doses (50, 100 and 200 mg/kg) respectively. The extract corrected major physiological alterations such as liver and kidney impairments, oxidative stress and architectural disorganization in liver, spleen and kidneys tissues. The UHPLC/MS analysis identified 7 compounds, namely chlorogenic acid, azulene, quercetin, rhodine, 1-ethyl-2,4-dimethyl benzene and phthalan. Out of seven compounds identified in the extract quercetin and phthalan showed higher in silico inhibitory activity against P. falciparum purine nucleoside phosphorylase and Plasmodium falciparum 6-phosphosgluconate dehydrogenase parasite enzymes. ConclusionThese findings indicate that H. asper could be a promising complementary medicine to manage malaria. Meanwhile, the affinity of annoted compounds with these enzymes should be further confirmed.

Antimalarial activity of cecropin antimicrobial peptides derived from Anopheles mosquitoes.

The emergence of clinically drug-resistant malaria parasites requires the urgent development of new drugs. Mosquitoes are vectors of multiple pathogens and have developed resistance mechanisms against them, which often involve antimicrobial peptides (AMPs). An-cecB is an AMP of the malaria-transmitting mosquito genus Anopheles, and we herein report its antimalarial activity against Plasmodium falciparum 3D7, the artemisinin-resistant strain 803, and the chloroquine-resistant strain Dd2 in vitro. We also demonstrate its anti-parasite activity in vivo, using the rodent malaria parasite Plasmodium berghei (ANKA). We show that An-cecB displays potent antimalarial activity and that its mechanism of action may occur through direct killing of the parasite or through interaction with infected red blood cell membranes. Unfortunately, An-cecB was found to be cytotoxic to mammalian cells and had poor antimalarial activity in vivo. However, its truncated peptide An-cecB-1 retained most of its antimalarial activity and avoided its cytotoxicity in vitro. An-cecB-1 also showed better antimalarial activity in vivo. Mosquito-derived AMPs may provide new ideas for the development of antimalarial drugs against drug-resistant parasites, and An-cecB has potential use as a template for antimalarial peptides.

Synthesis, design, and optimization of a potent and selective series of pyridylpiperazines as promising antimalarial agents

An optimization of the pyridylpiperazine series against Plasmodium falciparum has been performed, exploring a structure-activity relationship carried out on the toluyl fragment of hit 1, a compound with low micromolar activity against Plasmodium falciparum discovered by high-throughput screening. After confirming the crucial role played by this aryl fragment in the antiplasmodial activity, the replacement of the ortho-methyl substituent of 1 by halogenated ones led to an improvement for four analogs, either in terms of potency, expected pharmacokinetics profile, or both. Further introduction of endocyclic nitrogens in this fragment identified two more optimized compounds, 20 and 23, which are expected to be much more metabolically stable than 1. Additional assessment of the cytotoxicity, Ligand Lipophilic Efficiency, potency against the chloroquine-resistant Dd2 strain and in silico ADMET predictions revealed a satisfactory profile for most compounds, ultimately identifying the four optimized compounds 7, 9, 20 and 23 as promising compounds for further lead optimization of this series against Plasmodium falciparum.

Design, Synthesis, Antitumor, and Antiplasmodial Evaluation of New 7-Chloroquinoline-Benzimidazole Hybrids.

Newly synthesized 7-chloro-4-aminoquinoline-benzimidazole hybrids were characterized by NMR and elemental analysis. Compounds were tested for their effects on the growth of the non-tumor cell line MRC-5 (human fetal lung fibroblasts) and carcinoma (HeLa and CaCo-2), leukemia, and lymphoma (Hut78, THP-1, and HL-60) cell lines. The obtained results, expressed as the concentration at which 50% inhibition of cell growth is achieved (IC50 value), show that the tested compounds affect cell growth differently depending on the cell line and the applied dose (IC50 ranged from 0.2 to >100 µM). Also, the antiplasmodial activity of these hybrids was evaluated against two P. falciparum strains (Pf3D7 and PfDd2). The tested compounds showed potent antiplasmodial activity, against both strains, at nanomolar concentrations. Quantitative structure-activity relationship (QSAR) analysis resulted in predictive models for antiplasmodial activity against the 3D7 strain (R2 = 0.886; Rext2 = 0.937; F = 41.589) and Dd2 strain (R2 = 0.859; Rext2 = 0.878; F = 32.525) of P. falciparum. QSAR models identified the structural features of these favorable effects on antiplasmodial activities.

Stereochemical insights into enantioselective antiplasmodial lignanamides from the twigs and leaves of Solanum erianthum

Stereochemical investigations on the twigs and leaves of Solanum erianthum afforded five pairs of lignanamide enantiomers and a previously undescribed phenolic amide (3). Particularly, two pairs of previously undescribed lignanamide racemates (1a/1b–2a/2b) represent the first case of natural products that feature an unreported 5/5-fused N/O-biheterocyclic core. Their structures, including the absolute configurations, were determined unambiguously by using spectroscopic analyses and electronic circular dichroism calculations. A speculative biogenetic pathway for 1–3 was proposed. Interestingly, these lignanamides exhibited enantioselective antiplasmodial activities against drug-sensitive Plasmodium falciparum 3D7 strain and chloroquine-resistant Plasmodium falciparum Dd2 strain, pointing out that chirality plays an important role in drug development.

Repurposing DrugBank compounds as potential Plasmodium falciparum class 1a aminoacyl tRNA synthetase multi-stage pan-inhibitors with a specific focus on mitomycin

Plasmodium falciparum aminoacyl tRNA synthetases (PfaaRSs) are potent antimalarial targets essential for proteome fidelity and overall parasite survival in every stage of the parasite's life cycle. So far, some of these proteins have been singly targeted yielding inhibitor compounds that have been limited by incidences of resistance which can be overcome via pan-inhibition strategies. Hence, herein, for the first time, we report the identification and in vitro antiplasmodial validation of Mitomycin (MMC) as a probable pan-inhibitor of class 1a (arginyl(A)-, cysteinyl(C), isoleucyl(I)-, leucyl(L), methionyl(M), and valyl(V)-) PfaaRSs which hypothetically may underlie its previously reported activity on the ribosomal RNA to inhibit protein translation and biosynthesis. We combined multiple in silico structure-based discovery strategies that first helped identify functional and druggable sites that were preferentially targeted by the compound in each of the plasmodial proteins: Ins1-Ins2 domain in Pf-ARS; anticodon binding domain in Pf-CRS; CP1-editing domain in Pf-IRS and Pf-MRS; C-terminal domain in Pf-LRS; and CP-core region in Pf-VRS. Molecular dynamics studies further revealed that MMC allosterically induced changes in the global structures of each protein. Likewise, prominent structural perturbations were caused by the compound across the functional domains of the proteins. More so, MMC induced systematic alterations in the binding of the catalytic nucleotide and amino acid substrates which culminated in the loss of key interactions with key active site residues and ultimate reduction in the nucleotide-binding affinities across all proteins, as deduced from the binding energy calculations. These altogether confirmed that MMC uniformly disrupted the structure of the target proteins and essential substrates. Further, MMC demonstrated IC50 < 5 μM against the Dd2 and 3D7 strains of parasite making it a good starting point for malarial drug development. We believe that findings from our study will be important in the current search for highly effective multi-stage antimalarial drugs.

In vitro and in vivo antimalarial activities of the ethanol extract of Erythrina sigmoidea stem bark used for the treatment of malaria in the Western Region of Cameroon

BackgroundMalaria is one of the leading causes of morbidity and/or mortality in tropical Africa. The spread and development of resistance to chemical antimalarial drugs and the relatively high cost of the latter are problems associated with malaria control and are reasons to promote the use of plants to meet healthcare needs to treat malaria. The aim of this study was to evaluate antiplasmodial activities of extracts of Erythrina sigmoidea (Mah quat), which is traditionally used for the treatment of malaria in the western region of Cameroon.Material and methodsThe ethanol extract of E. sigmoidea stem bark was obtained through the maceration process using 95% ethanol, while the aqueous extract was prepared by infusion. The in vitro antiplasmodial effect of extracts against P. falciparum chloroquine-sensitive (3D7) and chloroquine-resistant (Dd2) strains was determined using the Trager and Jensen method. On the other hand, the in vivo antimalarial activity of the extract was evaluated in mice infected with Plasmodium berghei strain NK65 using the Peters’ 4-day suppressive test and Ryley test (curative test). A total of 36 mice were used, subdivided into six groups of six mice each: one normal control, a negative control, a positive control, and three other groups for the tested product. Blood samples were collected on the 10th day of each test for hematological parameters.ResultsThe aqueous extract had an in vitro antiplasmodial activity against the chloroquine-sensitive strain with an IC50 of 29.51 ± 3.63 µg/mL and against the chloroquine-resistant strain with an IC50 of 35.23 ± 3.17 µg/mL. The highest in vitro antiplasmodial activity was observed with the ethanol extract against the chloroquine-sensitive strain with an IC50 of 6.44 ± 0.08 µg/mL and against the chloroquine-resistant strain with an IC50 of 7.53 ± 0.22 µg/mL. The ethanol extract demonstrated suppressive activity in vivo with reduction rates of 87.69%, 86.79%, and 81.08% at doses of 500 mg/kg, 250 mg/kg, and 125 mg/kg, respectively; and curative activity in vivo with reduction rates of 80%, 78.5%, and 77.5% at doses of 500 mg/kg, 250 mg/kg, and 125 mg/kg, respectively. The number of white blood cells in the negative control (44.55 ± 5.02 103/µL) was higher compared to the other groups. As for the red blood cells, we observed a massive destruction of the latter in the infected and untreated group (5.82 ± 1.50 106/µL) compared to the infected and ethanol extract-treated groups (8.74 ± 1.57 106/µL for 500 mg/kg, 7.54 ± 1.77 106/µL for 250 mg/kg, and 8.9 ± 1.50 106/µL for 125 mg/kg).ConclusionThis study provides scientific data on the use of E. sigmoidea by the local population for the treatment of malaria. It shows that E. sigmoidea has antiplasmodial activity, and we also see that there are differences between the parameters that we have in the treated groups and those of the untreated group. However, toxicity tests are necessary to assess its safety.

Design, synthesis and Anti-Plasmodial activity of Mortiamide-Lugdunin conjugates

In this study, two linear and corresponding cyclic heptapeptide versions of mortiamide A-lugdunin hybrids were designed and synthesized by integrating an anti-malarial peptide epitope derived from Mortiamide A, combined with four residues known for their membrane interactions. Using this synthetic strategy, the sequence of mortiamide A was partly re-engineered with an epitope sequence of lugdunin along with an amino acid replacement using all-L and D/L configurations. Importantly, the re-engineered cyclic mortiamides with all-L (3) and D/L (4) configurations exhibited promising anti-malarial activities against the P. falciparum drug-sensitive TM4/8 strain with half-maximal inhibitory concentration (IC50) values of 6.2 ± 0.5 and 4.8 ± 0.1 μM, respectively. Additionally, they exhibited anti-malarial activities against the P. falciparum multidrug-resistant V1/S strain with IC50 values of 5.0 ± 2.6 and 3.7 ± 0.7 μM, respectively. Interestingly, a linear re-engineered mortiamide with D/L configuration (2) exhibited promising anti-malarial activities, surpassing those of the re-engineered cyclic mortiamides (3 and 4), against both the P. falciparum sensitive TM4/8 and multidrug-resistant V1/S strains with IC50 values of 3.6 ± 0.5 and 2.8 ± 0.7 μM (IC50 of Mortiamide A = 7.85 ± 0.97, 5.31 ± 0.24 μM against 3D7 and Dd2 strains) without any cytotoxicity at >100 µM. The presence of D/L forms in a linear structure significantly impacted the anti-malarial activity against both the P. falciparum sensitive TM4/8 strain and the multidrug-resistant V1/S strain.

Antiplasmodial activity and toxicity of the leaves, stem and roots of Parinari robusta Oliv [CHRYSOBALANACEAE] in animal model

Malaria continues to wreak havoc on various populations as a result of the mortality and economic burden associated with the disease. Progress made in the therapeutics of the disease is threatened by the emerging parasite resistance to currently used first line treatment drugs. This has prompted the search for new, effective, and safe antimalarial agents. Parinari robusta is one plant in use with inadequate evidence about its efficacy. This study therefore aimed to assess the in vivo and in vitro antimalarial potential, and the safety of the leaves, stem and roots of the plant. Acute toxicity was carried out according to OECD guidelines. In vivo antimalarial activity of the hydroethanolic extracts were assessed using the Peter's 4-day suppressive and Rane's curative tests. In vitro antiplasmodial activity of the hydroethanolic crude extracts were evaluated using the SYBR Green I fluorescence assay on the chloroquine sensitive (3D7) and chloroquine resistant (Dd2) strains of P. falciparum. P. robusta was safe with the lethal dose above 3000 mg/kg. All the extracts significantly (p < 0.001) suppressed parasitaemia in the Peter's suppressive and Rane's curative test in a dose dependent manner. The extracts showed highly to weakly active in vitro antiplasmodial activity with an IC50 between 2.629 μg/ml to 30.320 μg/ml against 3D7 and Dd2 strain of P. falciparum. Leaf and stem extract gave the most superior activity against the Dd2 and 3D7 P. falciparum strains. The findings of this study provide scientific evidence supporting the traditional use of P. robusta in the treatment of malaria.

Total Alkaloid content and In vitro Antiplasmodial activity of Grangea maderaspatana collected from Burkina Faso

Effective management of malaria remains a major concern for the scientific community mainly due to the resistance of Plasmodium falciparum to the common antimalarials. Many studies are conducted to identify plants that can fight against this disease. This work aimed to contribute to a better knowledge of antiplasmodial activity of different parts of Grangea maderaspatana (Asteracea). Thus, roots, flowers, leafy branches and whole plant of Grangea maderaspatana were extracted with hexane, dichloromethane, ethyl acetate and methanol. Alkaloid contents and antiplasmodial activity of extracts were respectively determined by bromocresol green method and enzyme-linked immunosorbent assay based on pLDH quantification. Total alkaloid contents ranged from 21.036 in methanolic extract of leafy branches to 1074.752µg qE/g in dichloromethane extract of whole plant. Extracts showed moderate to very active antiplasmodial effects. Antiplasmodial activity evaluated on chloroquino (CQ)-sensitive D10 and CQ-resistant Dd2 strains of Plasmodium falciparum showed that hexane and dichloromethane leafy branches extracts had a better activity. Alkaloid could be potentially responsible for antiplasmodial activity observed. None extract found to be toxic for cells at 50 and 100µg/ml. Dichloromethane extract of leafy branches could be a potential source of antiplasmodial molecules.

Synthesis of Novel Artemisinin, Ciprofloxacin, and Norfloxacin Hybrids with Potent Antiplasmodial Activity.

The synthesis and antiplasmodial evaluation of new hybrids combining the pharmacophore structures of artemisinin, ciprofloxacin or norfloxacin, and 7-chloroquinoline are reported in this study. The first step for all of the syntheses is the obtainment of key piperazine esters intermediates bearing the drugs ciprofloxacin and norfloxacin. Using these platforms, 18 final compounds were synthesized through a multistep procedure with overall yields ranging between 8 and 20%. All compounds were screened for their antiplasmodial activity against the chloroquine-resistant Plasmodium falciparum FcB1 strain. Compounds 20, 21, 22, and 28, bearing an artesunate fragment with ciprofloxacin, exhibited IC50 values in the range of 3.5-5.4 nM and excellent selectivity indices. Among the compounds bearing the artesunate moiety on the norfloxacin, two of them, 23 and 24, afforded IC50 values of 1.5 nM and 1.9 nM, respectively. They also showed excellent selectivity indices. The most potent compounds were also evaluated against the CQ-resistant Dd2 strain of Plasmodium falciparum, demonstrating that those compounds incorporating the artesunate fragment were the most potent. Finally, the combination of artesunate with either ciprofloxacin or norfloxacin moieties in a single molecular entity proved to substantially enhance the activity and selectivity when compared to the administration of the unconjugated counterparts artesunate/ciprofloxacin and artesunate/norfloxacin.

Antimalarial Drug Combination Predictions Using the Machine Learning Synergy Predictor (MLSyPred©) tool

PurposeAntimalarial drug resistance is a global public health problem that leads to treatment failure. Synergistic drug combinations can improve treatment outcomes and delay the development of drug resistance. Here, we describe the implementation of a freely available computational tool, Machine Learning Synergy Predictor (MLSyPred©), to predict potential synergy in antimalarial drug combinations.MethodsThe MLSyPred© synergy prediction method extracts molecular fingerprints from the drugs’ biochemical structures to use as features and also cleans and prepares the raw data. Five machine learning algorithms (Logistic Regression, Random Forest, Support vector machine, Ada Boost, and Gradient Boost) were implemented to build prediction models. Implementation and application of the MLSyPred© tool were tested using datasets from 1540 combinations of 79 drugs and compounds biologically evaluated in pairs for three strains of Plasmodium falciparum (3D7, HB3, and Dd2).ResultsThe best prediction models were obtained using Logistic Regression for antimalarials with the strains Dd2 and HB3 (0.81 and 0.70 AUC, respectively) and Random Forest for antimalarials with 3D7 (0.69 AUC). The MLSyPred© tool yielded 45% precision for synergistically predicted antimalarial drug combinations that were annotated and biologically validated, thus confirming the functionality and applicability of the tool.Conclusion The MLSyPred© tool is freely available and represents a promising strategy for discovering potential synergistic drug combinations for further development as novel antimalarial therapies.

Antimalarial mechanism of action of the natural product 9-methoxystrobilurin G.

The natural product 9-methoxystrobilurin G (9MG) from Favolaschia spp basidiomycetes is a potent and selective antimalarial. The mechanism of action of 9MG is unknown. We induced 9MG resistance in Plasmodium falciparum 3D7 and Dd2 strains and identified mutations associated with resistance by genome sequencing. All 9MG-resistant clones possessed missense mutations in the cytochrome b (CYTB) gene, a key component of mitochondrial complex III. The mutations map to the quinol oxidation site of CYTB, which is also the target of antimalarials such as atovaquone. In a complementary approach to identify protein targets of 9MG, a photoactivatable derivative of 9MG was synthesized and applied in chemoproteomic-based target profiling. Three components of mitochondrial complex III (QCR7, QCR9, and COX15) were specifically enriched consistent with 9MG targeting CYTB and complex III function in P. falciparum. Inhibition of complex III activity by 9MG was confirmed by ubiquinone cytochrome c reductase assay using P. falciparum extract. The findings from this study may be useful for developing novel antimalarials targeting CYTB.

S-MGBs bearing amidine tail groups are potent, selective antiplasmodial agents.

There were an estimated 249 million cases of malaria globally in 2022, causing approximately 608 000 deaths. Most of these are attributed to infection by P. falciparum. Strathclyde minor groove binders (S-MGBs) are a promising new class of anti-infective agent that have been shown to be effective against many infectious organisms, including P. falciparum. A panel of 25 S-MGBs was synthesised, including those bearing an amidine tail group, and their antiplasmodial activity against 3D7 and Dd2 strains was determined in vitro using an asexual P. falciparum imaging assay. Determination of activity against HEK293 cells allowed for selective cytotoxicity to be measured. DNA binding studies were carried out using native mass spectrometry and DNA thermal shift assays. A comparison of 3D7 (chloroquine sensitive) and Dd2 (chloroquine resistant) potency showed no evidence of cross-resistance across the S-MGB set. S-MGB-356, S-MGB-368 and S-MGB-359, amidine tail containing S-MGBs, were identified as the most promising hit compounds based on their selectivity indices (HEK293/3D7) of >612.6, >335.8 and >264.8, respectively. S-MGB-356, S-MGB-368 and S-MGB-359 were confirmed to bind to DNA as dimers, with gDNA thermal shifts (ΔT m) of 12 °C, 3 °C and 16 °C, respectively. Together, these data demonstrate that amidine tail bearing S-MGBs are promising hit compounds against P. falciparum, and can be further optimised into lead compounds.

Parallel Synthesis of Piperazine Tethered Thiazole Compounds with Antiplasmodial Activity.

Thiazole and piperazine are two important heterocyclic rings that play a prominent role in nature and have a broad range of applications in agricultural and medicinal chemistry. Herein, we report the parallel synthesis of a library of diverse piperazine-tethered thiazole compounds. The reaction of piperazine with newly generated 4-chloromethyl-2-amino thiazoles led to the desired piperazine thiazole compounds with high purities and good overall yields. Using a variety of commercially available carboxylic acids, the parallel synthesis of a variety of disubstituted 4-(piperazin-1-ylmethyl)thiazol-2-amine derivatives is described. the screening of the compounds led to the identification of antiplasmodial compounds that exhibited interesting antimalarial activity, primarily against the Plasmodium falciparum chloroquine-resistant Dd2 strain. The hit compound 2291-61 demonstrated an antiplasmodial EC50 of 102 nM in the chloroquine-resistant Dd2 strain and a selectivity of over 140.

New lignan glycosides from Justicia secunda Vahl (Acanthaceae) with antimicrobial and antiparasitic properties

Three new lignan glucosides, namely, justisecundosides A (1), B (2a), and C (2b), were isolated from the whole plant of Justicia secunda together with seven known compounds (3−9). Their structures were established based on a comprehensive analysis of HR-ESI-MS, IR, UV, and CD, in conjunction with their 1D and 2D-NMR data. A putative biogenetic pathway of compounds 1−2a,b from coniferyl alcohol was proposed. In addition, the antimicrobial activities of the extract, fractions, and some isolated compounds were assessed against multiresistant bacterial and fungal strains. Furthermore, the antiplasmodial, antileishmanial, and antitrypanosomal activities were assessed against the sensitive (3D7) and multidrug-resistant (Dd2) strains of P. falciparum, promastigote and bloodstream forms of L. donovani, and Trypanosoma brucei, respectively. Compound 4 exhibited moderate antibacterial activity against Staphylococcus aureus SA RN 46003 with a MIC value of 62.5 μg/mL. Besides, compound 6 demonstrated a very good activity against sensitive (IC50Pf3D7: 0.81 μg/mL) and multidrug-resistant (IC50PfDd2: 14.61 μg/mL) strains of P. falciparum while compound 4 displayed good antitrypanosomal activity (IC50: 1.19 μg/mL). Also, compound 1 was the most active on the promastigote form of L. donovani with an IC50 of 13.02 μg/mL.