Antimalarial Research Articles

Preventing the re-establishment of malaria during the COVID-19 pandemic in Sri Lanka: implications for health security

BackgroundThe COVID-19 pandemic—with its first reported case in Sri Lanka in March 2020—had the potential to impact the risk of re-establishing malaria, a disease which was eliminated from Sri Lanka in 2012. Post-elimination, the country remains highly vulnerable to a return of malaria on account of high vector mosquito densities and the inflow of imported malaria cases.MethodsParallels between COVID-19 and malaria after its elimination as health security threats were drawn, and the many ways in which the COVID-19 pandemic impacted the prevention of re-establishment of malaria programmes in the country in 2020 were examined. The implications of this experience for global health security are analysed.ResultsIn 2020, imported malaria cases were fewer than in the previous 3 years, due to restrictions on international travel. Yet, a high level of malaria case and entomological surveillance was sustained through surveillance strategies modified to focus on quarantine centers, in response to the pandemic. As a result, more imported malaria cases were detected by active case detection than by passive surveillance. Some of the operational shifts adopted by the Anti Malaria Campaign were moving rapidly into functioning as an intersectoral player by reinforcing its collaborations with the Ministries of Aviation and Defense, switching to the use of online communication systems, and integrating and synergizing its field activities with the COVID-19 control programme.ConclusionsThe experience highlights the need for disease control programmes to be agile, flexible and responsive, and underscores the importance of maintaining even a lean focal programme for diseases such as malaria after they have been eliminated. Sustaining public health leadership and robust technological capacities in communication and data management were paramount in preventing the disruption of the malaria prevention programme during the pandemic and sustaining the malaria-free status of the country.

Transferrin-Conjugated Nanostructured Lipid Carriers for Targeting Artemisone to Melanoma Cells.

We report a successful formulation of Artemisone (ATM) in transferrin (Tf)-conjugated nanostructured lipid carriers (NLCs), achieving nearly a five-times increase in cell toxicity. The escalating cost of new drug discoveries led to the repurposing of approved drugs for new indications. This study incorporated Artemisone, an antimalarial drug, into a nanostructured lipid carrier (NLC) and tested for possible anticancer effects. The aim was to develop NLCs, and transferrin-conjugated NLCs (NLC-Tf) encapsulating Artemisone to enhance its delivery and anticancer activity. NLC formulations were prepared using high-pressure homogenization followed by ultrasonication and were characterized by particle size, zeta potential, and PDI. The conjugation of (Tf) to (NLC) was confirmed using IR, and the anticancer activity was tested using MTS assay. All formulations were in the nanometer size range (140-167 nm) with different zeta potential values. IR spectroscopy confirmed the successful conjugation of transferrin to NLC. Upon testing the formulations on melanoma cell lines using MTS assay, there was a significant decrease in viability and an increase in the encapsulated ATM-Tf toxicity compared to positive control ATM. The NLCs presented a promising potential carrier for delivering ATM to melanoma cells, and further conjugation with Tf significantly improved the ATM cytotoxicity.

Assessment of Saliva and Urine Performance for Antimalarial Drug Resistance Molecular Markers Study

<i>Background</i>: The malaria diagnostic tools developed to date require blood to be taken. However, certain groups in the population are reluctant to take blood samples because of their cultural habits (blood taboo), or because of the fear associated with the trauma of the injection, especially when the sample is taken repeatedly. Saliva and urine, which are not very invasive to collect, have not been widely used for malaria diagnosis. The aim of this study is to assess the performance of saliva and urine in detecting molecular markers of <i>Plasmodium falciparum </i>resistance to antimalarial drugs. <i>Methodology</i>: Blood, urine and saliva samples were collected in three different localities from 94 patients over 2 years of age with microscopically confirmed <i>Plasmodium falciparum </i>uncomplicated malaria. <i>P. falciparum </i>genomic DNA (Deoxyribonucleic acid) was then extracted and amplified using primers specific for the <i>Pfcrt (Plasmodium falciparum Chloroquine Resistance Transporter), Pfdhfr (Plasmodium falciparum dihydrofolate reductase) </i>and <i>PfK13 propeller (Plasmodium falciparum Kelch13 propeller) </i>genes. The amplification products were processed by electrophoresis and analyzed against blood, saliva and urine samples. A multivariate statistical analysis in R programming environment was performed aiming to assess the performance of blood, saliva and urine samples in detecting molecular markers of <i>P. falciparum </i>resistance. <i>Results</i>: Agarose gel electrophoresis of the amplification products of each gene detected the <i>Pfcrt </i>genes at 80.85% (76/94), <i>Pfdhfr </i>at 95.74% (90/94) and <i>PfK13 Propeller </i>at 98.93% (93/94) in blood. In saliva, gene detection levels were 50% (47/94), 69.14% (65/94) and 4.26% (4/94) respectively for the <I>K13</I> propeller, <i>Pfdhfr</i> and <i>Pfcrt</i> genes. Unlike the <i>Pfcrt </i>gene, which was not detected, 45.74% (43/94) and 38.30% (36/94) of <i>PfK13</i> Propeller and <i>pfdhfr</i> genes respectively were detected in urine. Taking blood as the reference biological sample, statistical analysis showed that unlike urine, saliva exhibited a detection performance for molecular markers of antimalarial drug resistance (<i>pfcrt,</i> <i>pfdhfr</i>, <i>pfK13</i> propeller) close to that of blood (p < 0.05). The performance of saliva and urine was also assessed on the basis of the detection of the molecular markers <i>pfdhfr</i>, <i>pfcrt </i>and <i>pfK13 </i>using ROC (<i>receiver operational characteristic</i>) analysis. The data revealed a high sensitivity of saliva compared with urine in the detection of the <i>pfdhfr</i>, <i>pfcrt </i>and <i>pfK13 propeller </i>genes. <i>Conclusion</i>: The levels of detection of molecular markers of antimalarial drug resistance studied in saliva are close to those in blood. Saliva is a high-performance biological product that could potentially be used as an alternative non-invasive sample for the study of molecular markers of Plasmodium falciparum resistance to antimalarial drugs.

Challenges in Malaria Control and Prevention in East Africa

Malaria remains a critical public health issue in East Africa, where high transmission rates persist despite extensive control and prevention efforts. This review article explores the multifaceted challenges that hinder effective malaria control and prevention in the region, including the emergence of drug-resistant Plasmodium parasites, insecticide-resistant mosquito vectors, inadequate healthcare infrastructure, socio-economic barriers, and environmental factors. The review methodology involved analyzing recent studies, reports, and data from international health organizations. Drug resistance and vector control are significant issues, with resistance to both anti-malarial drugs and insecticides compromising treatment efficacy and prevention efforts. Additionally, socio-economic factors such as poverty and lack of education, coupled with climate variability and environmental changes, further complicate malaria control. Addressing these challenges requires a coordinated approach that integrates continuous monitoring, healthcare system strengthening, community engagement, and international collaboration. By tackling these issues, East Africa can improve its malaria control efforts and ultimately enhance the health outcomes of its populations. Keywords: Malaria Control, Drug Resistance, Insecticide Resistance, Healthcare Infrastructure, Socio-Economic Barriers.

Repurposed Drugs during the Outbreak of Pandemic COVID-19: A Mini-Review on Their Molecular Structures and Hit-and-Trial Results.

One of the most significant threats to global public health in the 21st century is the novel coronavirus disease (COVID-19) caused by SARS-CoV-2. It rapidly turned into a global pandemic after it was identified in late 2019, and the World Health Organization announced the end of the pandemic on May 5, 2023. Current strategies for managing this disease include vaccination and repurposing antimalarial and antibiotic medications to alleviate symptoms like fever and throat pain, which are associated with acute respiratory distress syndrome (ARDS). Antiviral drugs such as chloroquine, hydroxychloroquine, azithromycin, remdesivir, and favipiravir have been repurposed for the treatment of COVID-19. They were previously recommended for treating SARS-CoV and MERS-CoV. However, the inefficacy and adverse side effects of these repurposed drugs led to a decrease in their widespread use in treating COVID-19 patients. The lack of approved drugs for combating this coronavirus and its unpredictable variants remains a significant challenge.

Oleuropein mediated autophagy begets antimalarial drug resistance.

Drug resistance in Plasmodium falciparum presents a formidable challenge to the humanity. And, unavailability of an effective vaccine worsens the situation further. Autophagy is one of the mechanisms employed by parasite to evade drug pressure to survive. Autophagy induced by the P. falciparum in response to the oleuropein pressure may answer many questions related to the parasite survival as well as evolving drug tolerance. The survival/autophagy axis could be an important avenue to explore in order to address certain questions related to the evolution of drug resistance. In addition, humanized mouse model of P. falciparum infection could serve as an important preclinical tool to investigate the oleuropein-induced autophagy, potentially helping to dissect the mechanisms underlying the development of antimalarial drug resistance.

MalariaFlow: A comprehensive deep learning platform for multistage phenotypic antimalarial drug discovery

Malaria remains a significant global health challenge due to the growing drug resistance of Plasmodium parasites and the failure to block transmission within human host. While machine learning (ML) and deep learning (DL) methods have shown promise in accelerating antimalarial drug discovery, the performance of deep learning models based on molecular graph and other co-representation approaches warrants further exploration. Current research has overlooked mutant strains of the malaria parasite with varying degrees of sensitivity or resistance, and has not covered the prediction of inhibitory activities across the three major life cycle stages (liver, asexual blood, and gametocyte) within the human host, which is crucial for both treatment and transmission blocking. In this study, we manually curated a benchmark antimalarial activity dataset comprising 407,404 unique compounds and 410,654 bioactivity data points across ten Plasmodium phenotypes and three stages. The performance was systematically compared among two fingerprint-based ML models (RF::Morgan and XGBoost:Morgan), four graph-based DL models (GCN, GAT, MPNN, and Attentive FP), and three co-representations DL models (FP-GNN, HiGNN, and FG-BERT), which reveal that: 1) The FP-GNN model achieved the best predictive performance, outperforming the other methods in distinguishing active and inactive compounds across balanced, more positive, and more negative datasets, with an overall AUROC of 0.900; 2) Fingerprint-based ML models outperformed graph-based DL models on large datasets (>1000 compounds), but the three co-representations DL models were able to incorporate domain-specific chemical knowledge to bridge this gap, achieving better predictive performance. These findings provide valuable guidance for selecting appropriate ML and DL methods for antimalarial activity prediction tasks. The interpretability analysis of the FP-GNN model revealed its ability to accurately capture the key structural features responsible for the liver- and blood-stage activities of the known antimalarial drug atovaquone. Finally, we developed a web server, MalariaFlow, incorporating these high-quality models for antimalarial activity prediction, virtual screening, and similarity search, successfully predicting novel triple-stage antimalarial hits validated through experimental testing, demonstrating its effectiveness and value in discovering potential multistage antimalarial drug candidates.

Evaluation of the binding interactions between Plasmodium falciparum Kelch-13 mutant recombinant proteins with artemisinin.

Malaria, an ancient mosquito-borne illness caused by Plasmodium parasites, is mostly treated with Artemisinin Combination Therapy (ACT). However, Single Nucleotide Polymorphisms (SNPs) mutations in the P. falciparum Kelch 13 (PfK13) protein have been associated with artemisinin resistance (ART-R). Therefore, this study aims to generate PfK13 recombinant proteins incorporating of two specific SNPs mutations, PfK13-V494I and PfK13-N537I, and subsequently analyze their binding interactions with artemisinin (ART). The recombinant proteins of PfK13 mutations and the Wild Type (WT) variant were expressed utilizing a standard protein expression protocol with modifications and subsequently purified via IMAC and confirmed with SDS-PAGE analysis and Orbitrap tandem mass spectrometry. The binding interactions between PfK13-V494I and PfK13-N537I propeller domain proteins ART were assessed through Isothermal Titration Calorimetry (ITC) and subsequently validated using fluorescence spectrometry. The protein concentrations obtained were 0.3 mg/ml for PfK13-WT, 0.18 mg/ml for PfK13-V494I, and 0.28 mg/ml for PfK13-N537I. Results obtained for binding interaction revealed an increased fluorescence intensity in the mutants PfK13-N537I (83 a.u.) and PfK13-V494I (143 a.u.) compared to PfK13-WT (33 a.u.), indicating increased exposure of surface proteins because of the looser binding between PfK13 protein mutants with ART. This shows that the PfK13 mutations may induce alterations in the binding interaction with ART, potentially leading to reduced effectiveness of ART and ultimately contributing to ART-R. However, this study only elucidated one facet of the contributing factors that could serve as potential indicators for ART-R and further investigation should be pursued in the future to comprehensively explore this complex mechanism of ART-R.

Antimalarial analysis of pharmaceutical formulations and biological samples by capillary electrophoresis: the state of the art and applications.

Malaria is a serious public health problem, being an endemic disease in 84 countries, mainly in Africa. This review explores the application of capillary electrophoresis (CE) techniques for analyzing antimalarial drugs, highlighting methods from 2000 to 2023 for the analysis of pharmaceutical formulations and human biological samples. The versatility, selectivity, high efficiency, cost-effectiveness, and high analytical frequency of CE techniques have become attractive choices for pharmaceutical analysis, focusing on quality control and impurity analysis applications. The evolution of achiral and chiral electromigration methods has been described based on the features of each mode of separation: capillary zone electrophoresis (CZE), micellar electrokinetic chromatography, microemulsion electrokinetic chromatography, and capillary electrochromatography. As expected, CZE is reported in most articles owing to its compatibility with drug properties and separation mode. However, it is necessary to perform other separation modes for a few drugs that are present in neutral form. After exhaustive research using different databases and statistical analyses, 27 articles using CE techniques for antimalarial drug analysis were found and are mentioned in this review.

A comparative analysis of chloroplast genomes revealed the chloroplast heteroplasmy of Artemisia annua.

Artemisia annua L. is the main source of artemisinin, an antimalarial drug. High diversity of morphological characteristics and artemisinin contents of A. annua has affected the stable production of artemisinin while efficient discrimination method of A. annua strains is not available. The complete chloroplast (cp) genomes of 38 A. annua strains were assembled and analyzed in this study. Phylogenetic analysis of Artemisia species showed that distinct intraspecific divergence occurred in A. annua strains. A total of 38 A. annua strains were divided into two distinct lineages, one lineage containing widely-distributed strains and the other lineage only containing strains from northern China. The A. annua cp genomes ranged from 150, 953 to 150, 974bp and contained 131 genes, and no presence or absence variation of genes was observed. The IRs and SC junctions were located in rps19 and ycf1, respectively, without IR contraction observed. Rich sequence polymorphisms were observed among A. annua strains, and a total of 60 polymorphic sites representing 14 haplotypes were identified which unfolding the cpDNA heteroplasmy of A. annua. In conclusion, this study provided valuable resource for A. annua strains identification and provided new insights into the evolutionary characteristics of A. annua.

Efficacy of medicinal plants and their derived biomolecules against Plasmodium falciparum

Many apicomplexan pathogens pose significant threats to humans and domestic animals, with the lack of effective drugs and drug resistance representing major challenges in disease management. To address this, the search for new and potent antimalarial drugs is crucial. Plant-based formulations offer a promising alternative for such drug development. Here, we evaluated the in vitro antiplasmodial activity of nine plant extracts, traditionally used to treat fever-like symptoms in Bangladesh. We assessed the antimalarial activity of plant extracts by using the Plasmodium falciparum 3D7 growth inhibition assay, an invasion assay, and a cytotoxicity assay. Of the nine plants studied, ethanolic and methanolic leaf extracts of Ficus hispida, Streblus asper, and Boerhavia repens exhibited high antiplasmodial activity, with IC50 values of 9.31, 4.13, 9.63 μg/ml (ethanolic) and 15.12, 6.63, 7.58 μg/ml (methanolic), respectively, and minimal toxicity (cell viability >80%). Clerodendrum viscosum displayed antiplasmodial effects with IC50 values of 28.90 μg/ml (ethanolic) and 30.57 μg/ml (methanolic). Adhatoda vasica, Mussaenda corymbosa, and Amaranthus spinosus ethanolic extracts showed antimalarial effects with IC50 values of 61.78 μg/ml, 66.31 μg/ml, and 64.14 μg/ml, respectively. However, methanolic extracts of A. vasica and A. spinosus had IC50 values >100 μg/ml. The ethanolic and methanolic extracts of A. vasica, A. spinosus, F. hispida, S. asper, and B. repens significantly reduced parasitemia by inhibiting invasion into erythrocytes. This study highlights the robust antimalarial activity and low cytotoxicity of leaf extracts of F. hispida, S. asper, and B. repens, indicating the presence of antimalarial compounds that warrant further investigation.

Chemoproteomic Strategy Identifies PfUCHL3 as the Target of Halofuginone.

The human malaria parasite Plasmodium falciparum (P. falciparum) continues to pose a significant public health challenge, leading to millions of fatalities globally. Halofuginone (HF) has shown a significant anti-P. falciparum effect, suggesting its potential as a therapeutic agent for malaria treatment. In this study, we synthesized a photoaffinity labeling probe of HF to identify its direct target in P. falciparum. Our results reveal that ubiquitin carboxyl-terminal hydrolase 3 (PfUCHL3) acts as a crucial target protein of HF, which modulates parasite growth in the intraerythrocytic cycle. In particular, we discovered that HF potentially forms hydrogen bonds with the Leu10, Glu11, and Arg217 sites of PfUCHL3, thereby inducing an allosteric effect by promoting the embedding of the helix 6' region on the protein surface. Furthermore, HF disrupts the expression of multiple functional proteins mediated by PfUCHL3, specifically those that play crucial roles in amino acid biosynthesis and metabolism in P. falciparum. Taken together, this study highlights PfUCHL3 as a previously undisclosed druggable target of HF, which contributes to the development of novel anti-malarial agents in the future.

Hyperimmune malarial splenomegaly in a malaria-endemic area of southwest Burkina Faso: case of Bobo-Dioulasso

IntroductionHyperreactive malarial splenomegaly (HMS) is one of the main causes of massive splenomegaly in malaria-endemic zones. Diagnosis is often challenging in Bobo-Dioulasso. This study aimed to describe the clinical and socio-demographic profile, and the reasons for delay in the diagnosis of HMS cases recorded in the Medicine and Medical Specialties wards of Souro Sanou Teaching hospital.MethodsA retrospective descriptive study was conducted from August 2022 by focusing on HMS cases diagnosed in the Infectious Diseases and Clinical Hematology wards of Souro Sanou Teaching Hospital.ResultsOverall, 65 patients met our inclusion criteria over the 12-year period. Burkinabe nationals and have been residing in Burkina Faso since their birth. 79% (79%) of the patients were seen for medical consultation with the reason for consultation being a voluminous mass in the left hypochondrium. Indigence, self-medication, and lack of information were essential elements in late diagnosis of HMS in Bobo-Dioulasso. All patients were treated with a single tablet of Artemether (80 mg) and Lumefantrine (480 mg) in the morning and evening for 3 days, followed by sulfadoxine–pyrimethamine per week. Nine months later, patients were clinically asymptomatic.ConclusionThis study provides a database on hyperreactive malarial splenomegaly (HMS) in the south-west region of Burkina Faso. Rapid and accurate diagnosis of the disease and appropriate use of effective antimalarial drugs would significantly reduce the burden of HMS in Sub-Saharan African countries.

An Unusual Case of CNS Tuberculoma in a 19-Year-Old Man

Background: Tuberculosis (TB) is ranked as one of the top 10 causes of death. Mycobacterium tuberculosis (M. TB) infection, the causative organism for TB affects approximately a quarter of the global population placing a burden on the healthcare system. Central nervous system tuberculosis (CNS TB) is seen in 5 to 10% of extrapulmonary TB cases and has the highest mortality. CNS tuberculoma is one of its manifestation. Clinical presentation of CNS tuberculoma depends on its location within the CNS and commonly include headache, seizures, and focal neurological deficits, due to the presence of a space occupying lesion, although patients can be asymptomatic. We report the case of a 19yr old man who had an unusual presentation of CNS tuberculoma, highlighting its clinical presentation, diagnosis and treatment. Case Presentation: Index patient is a 19-year-old male college student who resides in a city. He presented with 15 days history of fever, headache, vomiting, vertigo, ataxia, and inability to concentrate. He received antimalarial, anti typhoid and body booster medications but had no improvement and had a history of weight loss despite no dietary change. He had never been diagnosed with TB and had all his childhood vaccinations given. Plain Magnetic Resonance Imaging (MRI) brain scan done revealed a posterior fossa mass lesion with perilesional edema. Futher, a contrast MRI brain scan showed multiple ring-enhancing conglomerates of lesion around the tentorium on the posterior fossa with intense contrast enhancement. The largest of this mass measured 4.5 cm x 2.5 cm x 2.5 cm in the right superior cerebellum compressing the 4th ventricle and with effacement of the cerebellopontine angle. Lastly, an MRI spectrometry revealed elevated lipid lactate peak. His chest x-ray was unremarkable. Other blood parameters were essentially within range with the exception of Erythrocyte ESR and mantoux test. He received antitubercular drug (Isoniazid, Rifampin, Pyrazinamide, Ethambutol, Levoflox and Streptomycin) for 18th months with complete remission. Conclusion: CNS tuberculomas are tuberculous masses that can be located anywhere from the brain to spinal cord. Advanced diagnostic modalities may guide clinicians towards making it's diagnosis. Treatment maybe medical (use of antitubercular drugs) or surgical excision with medical therapy being first choice. While the index patient had no obvious risk factors for his disease, his BCG vaccination pose a possible source of his exposure to TB infection. More research is needed on this however.

Targeted polymeric primaquine nanoparticles: optimization, evaluation, and in-vivo liver uptake for improved malaria treatment

Primaquine (PQ) is a widely used antimalarial drug, but its high dosage requirements can lead to significant tissue damage and adverse gastrointestinal and hematological effects. Recent studies have shown that nanoformulations can enhance the bioavailability of pharmaceuticals, thereby increasing efficacy, reducing dosing frequency, and minimizing toxicity. In this study, PQ-loaded PLGA nanoparticles (PQ-NPs) were prepared using a modified double emulsion solvent evaporation technique (w/o/w). The PQ-NPs exhibited a mean particle size of 228 ± 2.6 nm, a zeta potential of +27.4 mV, and an encapsulation efficiency of 81.3 ± 3.5%. Scanning electron microscopy (SEM) confirmed their spherical morphology, and the in vitro release profile demonstrated continuous drug release over 72 h. Differential scanning calorimetry (DSC) thermograms indicated that the drug was present in the nanoparticles, with improved physical stability. Fourier-transform infrared spectroscopy (FTIR) analysis showed no interactions between the various substances in the NPs. In vivo studies in Swiss albino mice infected with Plasmodium berghei revealed that the nanoformulated PQ was 20% more effective than the standard oral dose. Biodistribution studies indicated that 80% of the NPs accumulated in the liver, highlighting their potential for targeted drug delivery. This research demonstrates the successful development of a nanomedicine delivery system for antimalarial drugs, offering a promising strategy to enhance treatment efficacy while reducing adverse effects.

Enhancing the Intrinsic Antiplasmodial Activity and Improving the Stability and Selectivity of a Tunable Peptide Scaffold Derived from Human Platelet Factor 4.

The control of malaria, a disease caused by Plasmodium parasites that kills over half a million people every year, is threatened by the continual emergence and spread of drug resistance. Therefore, new molecules with different mechanisms of action are needed in the antimalarial drug development pipeline. Peptides developed from host defense molecules are gaining traction as anti-infectives due to theood of inducing drug resistance. Human platelet factor 4 (PF4) has intrinsic activity against P. falciparum, and a macrocyclic helix-loop-helix peptide derived from its active domain recapitulates this activity. In this study, we used a stepwise approach to optimize first-generation PF4-derived internalization peptides (PDIPs) by producing analogues with substitutions to charged and hydrophobic amino acid residues or with modifications to terminal residues including backbone cyclization. We evaluated the in vitro activity of PDIP analogues against P. falciparum compared to their overall helical structure, resistance to breakdown by serum proteases, selective binding to negatively charged membranes, and hemolytic activity. Next, we combined antiplasmodial potency-enhancing substitutions that retained favorable membrane and cell-selective properties onto the most stable scaffold to produce a backbone cyclic PDIP analogue with four-fold improved activity against P. falciparum compared to first-generation peptides. These studies demonstrate the ability to modify PDIP to select for and combine desirable properties and further validate the suitability of this unique peptide scaffold for developing a new molecule class that is distinct from existing antimalarial drugs.

Naringin and chloroquine combination mitigates chloroquine-resistant parasite-induced malaria pathogenesis by attenuating the inflammatory response

BackgroundMalaria, characterised by inflammation and multi-organ complications, needs novel chemotherapeutics due to the rise of drug-resistant malaria parasites, which is a serious health issue. Naringin (NGN), a flavanone glycoside (naringenin 7-O-neohesperidose), has a broad spectrum of pharmacological activities but its effect against malaria, alone and in combination, was not deeply investigated. PurposeTo assess the pharmacological efficacy of NGN alone and in combination with chloroquine (CQ) against a Plasmodium strain resistant to CQ and to elucidate its potential mode of action. MethodsThe anti-inflammatory potential of NGN was assessed in mouse microglial cells stimulated with hemozoin by analyzing inflammatory cytokines production. The anti-plasmodial potential of NGN was subsequently tested alone and in combination with CQ against the K1 strain of Plasmodium using the fixed ratio combination method. Further, we evaluated NGN's antimalarial efficacy against the CQ-resistant Plasmodium yoelii nigeriensis N67 strain (P. yoelii), both alone and in combination with CQ, by measuring parasitemia and survival rates. To comprehend the impact of NGN on malaria-induced inflammation in mice, we measured pro-inflammatory cytokines elevated by activated NF-кB signalling. These findings were supported by mRNA and immunohistochemical analyses of malaria-infected mice's liver and brain tissues. ResultsOur study demonstrated that NGN displayed anti-plasmodial activity, which was further augmented when combined with CQ. At 50 µM, NGN significantly reduced the elevation of pro-inflammatory cytokines in synthetic hemozoin-stimulated microglial cells. Compared to P. yoelii-infected mice, NGN (12.5 mg kg-1) significantly reduced parasitemia in mice, resulting in a survival period of up to 13 days. Survival improved by up to 20 days when NGN and CQ were given in combination. NGN, as revealed by immunohistochemical examination of brain and liver tissues, interfered with the NF-кB pathway, potentially reducing the elevation of pro-inflammatory cytokines (TNF-α, IL-1β, IL-18, IFN-γ, and IL-6). This was supported by the overexpression of inflammation-regulatory genes (TGFβ, Nrf2, HO-1, and iNOS) and the downregulation of inflammation-stimulating genes (NF-κB, NLRP3, and caspase-1). Histopathological analysis demonstrated the potential of NGN to restore liver and brain tissues to normal. The substantial decrease in the expression and production of ICAM-1 protein in the brain tissue implies the beneficial effects of NGN, pointing towards its potential for mitigating brain pathology. ConclusionThe findings of this study revealed NGN as a promising drug-like candidate for the management of CQ-resistant parasite-induced malaria pathogenesis for adjunctive therapy in combination with standard antimalarial drugs through its modulation of the NF-κB-mediated inflammation.

Chloroformate-mediated ring cleavage of indole alkaloids leads to re-engineered antiplasmodial agents.

Natural product ring distortion strategies have enabled rapid access to unique libraries of stereochemically complex compounds to explore new chemical space and increase our understanding of biological processes related to human disease. Herein is described the development of a ring-cleavage strategy using the indole alkaloids yohimbine, apovincamine, vinburnine, and reserpine that were reacted with a diversity of chloroformates paired with various alcohol/thiol nucleophiles to enable the rapid synthesis of 47 novel small molecules. Ring cleavage reactions of yohimbine and reserpine produced two diastereomeric products in moderate to excellent yields, whereas apovincamine and vinburnine produced a single diastereomeric product in significantly lower yields. Free energy calculations indicated that diastereoselectivity regarding select ring cleavage reactions from yohimbine and apovincamine is dictated by the geometry and three-dimensional structure of reactive cationic intermediates. These compounds were screened for antiplasmodial activity due to the need for novel antimalarial agents. Reserpine derivative 41 was found to exhibit interesting antiplasmodial activities against Plasmodium falciparum parasites (EC50 = 0.50 μM against Dd2 cultures), while its diastereomer 40 was found to be three-fold less active (EC50 = 1.78 μM). Overall, these studies demonstrate that the ring distortion of available indole alkaloids can lead to unique compound collections with re-engineered biological activities for exploring and potentially treating human disease.

An Interpretable Machine Learning Strategy for Antimalarial Drug Discovery with LightGBM and SHAP

Malaria continues to pose a significant global health threat, and the emergence of drug-resistant malaria exacerbates the challenge, underscoring the urgent need for new antimalarial drugs. While several machine learning algorithms have been applied to quantitative structure-activity relationship (QSAR) modeling for antimalarial compounds, there remains a need for more interpretable models that can provide insights into the underlying mechanisms of drug action, facilitating the rational design of new compounds. This study develops a QSAR model using Light Gradient Boosting Machine (LightGBM). The model is integrated with SHapley Additive exPlanations (SHAP) to enhance interpretability. The LightGBM model demonstrated superior performance in predicting antimalarial activity, with an ac-curacy of 86%, precision of 85%, sensitivity of 81%, specificity of 89%, and an F1-score of 83%. SHAP analysis identified key molecular descriptors such as maxdO and GATS2m as significant contributors to antimalarial activity. The integration of LightGBM with SHAP not only enhances the predictive ac-curacy of the QSAR model but also provides valuable insights into the importance of features, aiding in the rational design of new antimalarial drugs. This approach bridges the gap between model accuracy and interpretability, offering a robust framework for efficient and effective drug discovery against drug-resistant malaria strains.

Cimicifugin, a broad-spectrum inhibitor of Theileria annulata and Plasmodium falciparum CDK7.

Cyclin-dependent kinase 7 is an attractive therapeutic target for the treatment of cancers, and a previous report suggested that Plasmodium falciparum CDK7 is a potential drug target for developing new anti-malarial drugs. In this study, we aimed to characterize and evaluate the drug target potential of Theileria annulata CDK7. Theileria annulata is responsible for tropical theileriosis, which induces a phenotype similar to cancerous cells like immortalization, hyperproliferation, and dissemination. Virtual screening of the MyriaScreen II library predicted 14 compounds with high binding energies to the ATP-binding pocket of TaCDK7. Three compounds (cimicifugin, ST092793, and ST026925) of these 14 compounds were non-cytotoxic to the uninfected bovine cells (BoMac cells). Cimicifugin treatment led to the activation of the extrinsic apoptosis pathway and induced autophagy in T. annulata-infected cells. Furthermore, cimicifugin also inhibited the growth of P. falciparum, indicating that it has both anti-theilerial and anti-malarial activities and that TaCDK7 and PfCDK7 are promising drug targets.