Potential Antimalarials Research Articles

Synthesis, molecular modelling studies of artemisinin-chalcone derivatives and their antimalarial activity evaluation

Twenty-two monomers and dimers of artemisinin having chalcone as a linker were synthesised, and their antimalarial activity against Plasmodium falciparum was determined, and a quantitative structure-activity relationship (QSAR) was developed. Artemisinin is a frontline antimalarial drug known worldwide but is threatened because of the rapidly emerging artemisinin-resistant strain Plasmodium falciparum. In vitro, antimalarial IC50 (half-maximal inhibitory concentration) activity of a molecule against malaria parasites provides a good first screen for identifying the antimalarial potential of a particular molecule. The most active compound was artemisinin dimer dimethoxy chalcone as a linker (22) with IC50 of 4.34 nM. The molecular mechanism was explored through in silico docking & ADMET studies for the active compounds.

Quinoline-1,2,3-triazole hybrids: Design, synthesis, antimalarial and antimicrobial evaluation

A new library of Quinoline appended 1,2,3-triazole hybrids of biotic interest was synthesized using terminal alkynes containing quinoline moiety, benzyl amine based bromides, sodium azide via click chemistry protocol and were assessed for antimalarial and antimicrobial potential. All of the synthesized triazoles were characterized using different spectral techinques viz. FTIR, 1H NMR,13C NMR and HRMS. Antimalarial activity of the synthesized quinoline-triazole hybrids against the Plasmodium falciparum strain displayed modest to good results. The synthesized compounds also reflected good antimicrobial potential against four bacteria (Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae, Escherichia coli) and two fungi (Candida albicans, Aspergillus niger). Molecular docking studies and in-silico ADME (Absorption, Distribution, Metabolism and Elimination) analysis were also performed to check the binding and drug-likeliness of the synthesized compounds.

3-Position Biaryl Endochin-like Quinolones with Enhanced Antimalarial Performance.

ELQ-300 is a potent antimalarial drug with activity against blood, liver, and vector stages of the disease. A prodrug, ELQ-331, exhibits reduced crystallinity and improved in vivo efficacy in preclinical testing, and currently, it is in the developmental pipeline for once-a-week dosing for oral prophylaxis against malaria. Because of the high cost of developing a new drug for human use and the high risk of drug failure, it is prudent to have a back-up plan in place. Here we describe ELQ-596, a member of a new subseries of 3-biaryl-ELQs, with enhanced potency in vitro against multidrug-resistant Plasmodium falciparum parasites. ELQ-598, a prodrug of ELQ-596 with diminished crystallinity, is more effective vs murine malaria than its progenitor ELQ-331 by 4- to 10-fold, suggesting that correspondingly lower doses could be used to protect and cure humans of malaria. With a longer bloodstream half-life in mice compared to its progenitor, ELQ-596 highlights a novel series of next-generation ELQs with the potential for once-monthly dosing for protection against malaria infection. Advances in the preparation of 3-biaryl-ELQs are presented along with preliminary results from experiments to explore key structure-activity relationships for drug potency, selectivity, pharmacokinetics, and safety.

Pre-clinical studies comparing the anti-inflammatory potential of artemisinic compounds by targeting NFκB/TNF-α/NLRP3 and Nrf2/TRX pathways in Balb/C mice.

Artemisinin, artemether, artesunate, and dihydroartemisinin are renowned for their antimalarial potential. The current study aims to repurpose the above-mentioned artemisinic compounds (ACs) by conducting an intercomparison to evaluate their antiinflammatory potential (AIP). In order to develop potential candidates for the evaluation of AIP of ACs (50 and 100 mg/kg BW), carbon tetrachloride (1ml/kg body weight (BW)) was administered intraperitoneally to BALB/c mice. Alterations in animal behavior were assessed weekly through tail suspension test, force swim test, open field test, Y-maze test, inverted screen analysis, and weight lifting test. Aberrations in hematological, serological, endogenous antioxidants, and oxidative stress marker profiles were assessed in all twelve groups. Histological alterations were read using hematoxylin and eosin staining. Levels of inflammatory markers including nuclear factor kappa B (NF-κB), tumor necrosis factor alpha (TNF-α), and nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), were determined using immunohistochemical analysis (IHCA). Antioxidant markers i.e., nuclear factor erythroid-2-related factor (Nrf-2) and thioredoxin (TRX) were also quantified through IHCA. Comet assay was performed to quantify DNA damage. Oral administration of ACs to mice significantly alleviated the carbon tetrachloride induced inflammation in comparison with silymarin. Reduced levels of several inflammatory markers including nitric oxide, thiobarbituric acid reactive substances, interleukin-1 beta, NF-κB, TNF-α, and NLRP3, underscore the substantial AIP of ACs. IHCA depicted the revitalized percent relative expression of Nrf-2 and TRX in groups treated with ACs. Behavioral analysis revealed that ACs-treated groups significantly (p<0.05) attenuated the memory deficit, anxiety, and depressive-like behavior. Moreover, histopathological, hematological, serological, and endogenous antioxidant profiles indicated substantial AIP of ACs. Findings of comet assay further bolstered the compelling evidence as DNA damage was significantly (p<0.05) curbed down after ACs (100 mg/kg) treatment. All these outcomes implied that ACs exhibited AIP in a dose-dependent manner with maximal AIP imparted by artemisinin (100 mg/kg). This pre-clinical investigation avers the tremendous AIP of ACs targeting key molecular pathways. The current study divulges artemisinin as the most potent antiinflammatory agent among the tested compounds.

In vivo antimalarial efficacy of Artemisia afra powder suspensions

BackgroundA global death toll of 608,000 in 2022 and emerging parasite resistance to artemisinin, the mainstay of antimalarial chemotherapy derived from the Chinese herb Artemisia annua, urge the development of novel antimalarials. A clinical trial has found high antimalarial potency for aqueous extracts of A. annua as well as its African counterpart Artemisia afra, which contains only trace amounts of artemisinin. The artemisinin-independent antimalarial activity of A. afra points to the existence of other antimalarials present in the plant. However, the publication was retracted due to ethical and methodological concerns in the trial, so the only evidence for antimalarial activity of A. afra is built on in vitro studies reporting efficacy only in the microgram per milliliter range. HypothesisOur study aims to shed more light on the controversy around the antimalarial activity of A. afra by assessing its efficacy in mice. In particular, we are testing the hypothesis that A. afra contains a pro-drug that is inactive in vitro but active in vivo after metabolization by the mammalian host. MethodsPlasmodium berghei-infected mice were treated once or thrice (on three consecutive days) with various doses of A. afra, A. annua, or pure artemisinin. ResultsAqueous powder suspensions of A. annua but not A. afra showed antimalarial activity in mice. ConclusionOur experiments conducted in mice do not support the pro-drug hypothesis.

Synthesis and characterization of silver nanoparticle conjugated-chalcones and their evaluation for antimalarial, cytotoxicity and haemolytic potential at in vitro level

Silver nanoparticles (AgNPs) have shown a wide range of antimicrobial activities over the last 2 decades, but little is known about their antimalarial activity. Therefore, in the present study, AgNPs were surface functionalized by chalcones to create an efficient bioactive molecular surface that can enhance the antimalarial competency of both chalcones as well as chemically synthesized AgNPs. The AgNPs-conjugated chalcones have been synthesized using a chemical method employing the EDC-NHS coupling method. The characterization of AgNPs and AgNPs-conjugated chalcones was done through various analytical techniques. The SYBR Green I assay was performed for in vitro antimalarial activity, and cell cytotoxicity was done on HeLa cell line with MTT assay to calculate the IC50 and CC50, respectively. Haemolytic effect on fresh RBCs of these nanoconjugates were observed for 3 h and 24 h. AgNPs and AgNPs-conjugated chalcones have spectra at 420 nm and between 350 and 375 nm, respectively. The IC50 values of all the three conjugates for antimalarial activity ranged from 0.30 to 0.80 μg/mL. The present study provides a new method of synthesizing AgNPs-conjugated chalcones. Also, these synthesized conjugates show better antimalarial potential and reduced cellular toxicity compared to bared chalcones under an in vitro culture system. However, a further pre-clinical study on the murine model of malaria along with toxicity parameters is needed to provide more clarity.Graphical abstract

Phytochemical evaluation of Ziziphus mucronata and Xysmalobium undulutum towards the discovery and development of anti-malarial drugs

BackgroundThe development of resistance by Plasmodium falciparum is a burdening hazard that continues to undermine the strides made to alleviate malaria. As such, there is an increasing need to find new alternative strategies. This study evaluated and validated 2 medicinal plants used in traditional medicine to treat malaria.MethodsInspired by their ethnobotanical reputation of being effective against malaria, Ziziphus mucronata and Xysmalobium undulutum were collected and sequentially extracted using hexane (HEX), ethyl acetate (ETA), Dichloromethane (DCM) and methanol (MTL). The resulting crude extracts were screened for their anti-malarial and cytotoxic potential using the parasite lactate dehydrogenase (pLDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, respectively. This was followed by isolating the active compounds from the DCM extract of Z. mucronata using silica gel chromatography and structural elucidation using spectroscopic techniques (NMR: 1H, 12C, and DEPT). The active compounds were then targeted against P. falciparum heat shock protein 70–1 (PfHsp70-1) using Autodock Vina, followed by in vitro validation assays using ultraviolet–visible (UV–VIS) spectroscopy and the malate dehydrogenase (MDH) chaperone activity assay.ResultsThe extracts except those of methanol displayed anti-malarial potential with varying IC50 values, Z. mucronata HEX (11.69 ± 3.84 µg/mL), ETA (7.25 ± 1.41 µg/mL), DCM (5.49 ± 0.03 µg/mL), and X. undulutum HEX (4.9 ± 0.037 µg/mL), ETA (17.46 ± 0.024 µg/mL) and DCM (19.27 ± 0.492 µg/mL). The extracts exhibited minimal cytotoxicity except for the ETA and DCM of Z. mucronata with CC50 values of 10.96 and 10.01 µg/mL, respectively. Isolation and structural characterization of the active compounds from the DCM extracts revealed that betulinic acid (19.95 ± 1.53 µg/mL) and lupeol (7.56 ± 2.03 µg/mL) were responsible for the anti-malarial activity and had no considerable cytotoxicity (CC50 > µg/mL). Molecular docking suggested strong binding between PfHsp70-1, betulinic acid (− 6.8 kcal/mol), and lupeol (− 6.9 kcal/mol). Meanwhile, the in vitro validation assays revealed the disruption of the protein structural elements and chaperone function.ConclusionThis study proves that X undulutum and Z. mucronata have anti-malarial potential and that betulinic acid and lupeol are responsible for the activity seen on Z. mucronata. They also make a case for guided purification of new phytochemicals in the other extracts and support the notion of considering medicinal plants to discover new anti-malarials.

In silico analysis of soybean phytocompounds against Plasmodium falciparum

IntroductionNatural products have been indispensable since immemorial and still act as a supportive healer. Parasitic diseases are a significant hurdle for humans and are responsible for global morbidity and mass mortality. Due to the building up of resistance in parasites over existing drugs and the severe side effects of the drugs, there is an urgent need to explore various plant extracts to discover novel antiparasitic agents. This article deals with the pharmacological aspects of soybeans against Plasmodium falciparum, which causes many of the deadliest and most popular diseases, such as malaria. MethodsThe molecular basis for selective inhibition of soy phytoconstituents like beta-sitosterol, soya-saponin I, soya-saponin II, soya-saponin II methyl ester, dehydrosoyasaponin I, phytic acid, and tryptophyl leucine were evaluated using in silico molecular docking approaches and molecular dynamic simulations against the falcipain-2 (FP2) and phosphoethanolamine methyltransferase (PMT) of P. falciparum. ResultsThe results indicated that tryptophyl leucine exhibited potential inhibitory action against both enzymes based on pharmacophore, molecular docking, simulations, root mean square deviation, root mean square fluctuations, absorption, distribution, metabolism, excretion, and toxicity analyses. ConclusionMedicinal plants represent a treasure for bioactive lead compounds and eventually provide scope for further identification and investigation of novel drug candidates which may be important in the design of selective PfPMT/PfFP-2 inhibitors as potential antimalarials.

Evaluation of genotoxic damage, production reactive oxygen and nitrogen species in Plasmodium yoelii yoelii exposed to sodium metavanadate

Malaria represents the greatest global health burden among all parasitic diseases, with drug resistance representing the primary obstacle to control efforts. Sodium metavanadate (NaVO3) exhibits antimalarial activity against the Plasmodium yoelii yoelii (Pyy), yet its precise antimalarial mechanism remains elusive. This study aimed to assess the antimalarial potential of NaVO3, evaluate its genotoxicity, and determine the production of reactive oxygen and nitrogen species (ROS/RNS) in Pyy. CD-1 mice were infected and divided into two groups: one treated orally with NaVO3 (10 mg/kg/day for 4 days) and the other untreated. A 50% decrease in parasitemia was observed in treated mice. All experimental days demonstrated DNA damage in exposed parasites, along with an increase in ROS and RNS on the fifth day, suggesting a possible parasitostatic effect. The results indicate that DNA is a target of NaVO3, but further studies are necessary to fully elucidate the mechanisms underlying its antimalarial activity.

Evaluation of the antiplasmodial and anti-Toxoplasma activities of several Indonesian medicinal plant extracts

Ethnopharmacological relevanceMalaria, caused by Plasmodium parasites, remains a significant global health challenge, particularly in tropical and subtropical regions. At the same time, the prevalence of toxoplasmosis has been reported to be 30% worldwide. Traditional medicines have long played a vital role in discovering and developing novel drugs, and this approach is essential in the face of increasing resistance to current antimalarial and anti-Toxoplasma drugs. In Indonesian traditional medicine, various plants are used for their therapeutic properties. This study focuses on eleven medicinal plants from which nineteen extracts were obtained and screened for their potential medicinal benefits against malaria and toxoplasmosis. Aims of the studyThe aim of this study was to evaluate the efficacy of extracts from Indonesian medicinal plants to inhibit Plasmodium falciparum, a parasite responsible for malaria, and Toxoplasma gondii, an opportunistic parasite responsible for toxoplasmosis. MethodsNineteen extracts from eleven plants were subjected to in vitro screening against P. falciparum 3D7 (a chloroquine-sensitive strain) and the T. gondii RH strain. In vitro treatments were conducted on P. falciparum 3D7 and K1 (multidrug-resistant strains) using the potent extracts, and in vivo assessments were carried out with mice infected with P. yoelii 17XNL. LCMS analysis was also conducted to identify the main components of the most effective extract. ResultsSeven extracts showed significant antiplasmodial activity (>80% inhibition) at a concentration of 100 μg/ml. These extracts were obtained from Dysoxylum parasiticum (Osbeck) Kosterm., Elaeocarpus glaber (Bl.) Bijdr., Eleutherine americana Merr., Kleinhovia hospita L., Peronema canescens Jack, and Plectranthus scutellarioides (L.) R.Br. Notably, the D. parasiticum ethyl acetate extract exhibited high selectivity and efficacy both in vitro and in vivo. Herein, the key active compounds oleamide and erucamide were identified, which had IC50 values (P. falciparum 3D7/K1) of 17.49/23.63 μM and 32.49/51.59 μM, respectively. ConclusionsThe results of this study highlight the antimalarial potential of plant extracts collected from Indonesia. Particularly, extracts from D. parasiticum EtOH and EtOAc stood out for their low toxicity and strong antiplasmodial properties, with the EtOAc extract emerging as a notably promising antimalarial candidate. Key compounds identified within this extract demonstrate the complexity of extracts' action against malaria, potentially targeting both the parasite and the host. This suggests a promising approach for developing new antimalarial strategies that tackle the multifaceted challenges of drug resistance and disease management. Future investigations are necessary to unlock the full therapeutic potential of these extracts.

Effect of Formulated Cookies from Pleurotus Pulmonarius Flour on Parasitemia Level and Hematological Indices in Plasmodium Berghei (Nk–65 Strain) Infected Mice

A nutritious supplement that has both nutritional and therapeutic qualities is the mushroom. Malaria is a potentially fatal illness that strikes a wide range of individuals worldwide, with Nigeria having the highest incidence in Africa. It typically appears when the immune system is weakened. The antimalarial potential of cookies containing various formulations of Pleurotus Pulmonarius (10, 15, 20, and 25%) was examined in this study. It was examined how the cookies affected the mice’s weight, temperature, parasitemia level, and hematological indicators.

Exploring the modulatory influence on the antimalarial activity of amodiaquine using scaffold hybridisation with ferrocene integration

Amodiaquine (AQ) is a potent antimalarial drug used in combination with artesunate as part of artemisinin-based combination therapies (ACTs) for malarial treatment. Due to the rising emergence of resistant malaria parasites, some of which have been reported for ACT, the usefulness of AQ as an efficacious therapeutic drug is threatened. Employing the organometallic hybridisation approach, which has been shown to restore the antimalarial activity of chloroquine in the form of an organometallic hybrid clinical candidate ferroquine (FQ), the present study utilises this strategy to modulate the biological performance of AQ by incorporating ferrocene. Presently, we have conceptualised ferrocenyl AQ derivatives and have developed facile, practical routes for their synthesis. A tailored library of AQ derivatives was assembled and their antimalarial activity evaluated against chemosensitive (NF54) and multidrug-resistant (K1) strains of the malaria parasite, Plasmodium falciparum. The compounds generally showed enhanced or comparable activities to those of the reference clinical drugs chloroquine and AQ, against both strains, with higher selectivity for the sensitive phenotype, mostly in the double-digit nanomolar IC50 range. Moreover, representative compounds from this series show the potential to block malaria transmission by inhibiting the growth of stage II/III and V gametocytes in vitro. Preliminary mechanistic insights also revealed hemozoin inhibition as a potential mode of action.

Oral acute toxicity study and in vivo antimalarial activity of Strychnos lucida R. Br. tablet

Ethnopharmacological relevanceMalaria eradication has been a major goal of the Indonesian government since 2020. Medicinal plants, such as Strychnos lucida R. Br., are empirically used to treat malaria through traditional preparation methods. However, the safety and efficacy of these plants have not yet been confirmed. Therefore, further investigations are necessary to confirm the safety and efficacy of S. lucida as an antimalarial agent. Aims of the studyTo quantify the concentration of brucine in the S. lucida extract, determine the acute oral toxicity of the standardized extract, and evaluate the in vivo antimalarial potency of S. lucida tablet (SLT). Materials and methodsAcute oral toxicity of S.lucida extract was determined using the Organization for Economic Co-operation and Development 420 procedure, and the analytical method for brucine quantification was validated using high-performance liquid chromatography. In addition, antimalarial activity was determined using the Peter's four-day suppressive method. ResultsAcute toxicity analysis revealed S. lucida as a low-toxicity compound with a cut-off median lethal dose of 2000–5000 mg/kg body weight [BW], which was supported by the hematological and biochemical profiles of the kidneys, liver, and pancreas (p > 0.05). Extract standardization revealed that S. lucida contained 3.91 ± 0.074% w/w brucine, adhering to the limit specified in the Indonesian Herbal Pharmacopeia. Antimalarial test revealed that SLT inhibited the growth of Plasmodium berghei by 27.74–45.27%. Moreover, SLT improved the hemoglobin and hematocrit levels. White blood cell and lymphocyte counts were lower in the SLT-treated group than in the K (+) group (p < 0.05). ConclusionHistopathological and biochemical evaluations revealed that S. lucida extract was safe at a dose of 2000 mg/kg BW with low toxicity. SLT inhibited Plasmodium growth and improved the hemoglobin, hematocrit, and red blood cell profiles. Additionally, SLT reduced the lymphocyte and WBC counts and increased the monocyte and thrombocyte counts as part of the immune system response against Plasmodium infection.

Antimalarial potential of Kerala Ayurvedic Water "Pathimugam".

The persistent threat of drug resistant malaria demands new cures. Low prevalence of malaria in the Indian state of Kerala compared with other proximal states led us to explore if there is any traditional practice in Kerala which may confer protection against malaria. In this context, our attention was drawn to "Pathimugam" i.e., Ceasalpinia sappan whose heartwood is used to prepare a red aqueous extract which is a uniquely popular drink all over Kerala. Aqueous and methanolic extracts of various organs of C. sappan were prepared and tested against Plasmodium falciparum grown in vitro culture using SYBR Green-I assay. The cytotoxicity of active extracts/fractions was studied using mammalian HeLa cell line. In vivo efficacy was determined using Plasmodium berghei ANKA infected mice. The highest antiplasmodial activities in the alcoholic and aqueous extracts were observed in leaf methanolic extract (IC 2 μg/ml) and heartwood aqueous extract (IC 12.5 μg/ml). C. sappan extracts were equipotent against both chloroquine sensitive Pf3D7 and resistant Pf INDO strains and showed suppression of % parasitemia in P. berghei infected mice. Activity guided chromatographic fractionation of aqueous wood extract led to the fortification of antiplasmodial activity (IC 5 μg/ml). Our results establish the antiplasmodial potential of C. sappan and suggest that its regular use might have prophylactic or curative actions that may assist in keeping check on malaria in the Indian state of Kerala.

Unveiling the antimalarial properties of Terminalia ivorensis (A. Chev) stem bark aqueous extract: In vivo efficacy testing and in silico predictions

Due to the spreading resistance to antimalarial drugs, new therapeutics are urgently needed, preferably with novel modes of action. Extracts from Terminalia ivorensis have previously been shown to possess activity in vitro against multidrug-resistant and drug-sensitive strains of Plasmodium falciparum. However, to the best of our knowledge, no scientific study has been published describing the antimalarial potential of these extracts through in vivo efficacy testing. This study aimed to determine the safety and antimalarial efficacy of the T. ivorensis stem bark aqueous extract (TiH2O) in a mouse model using the OECD 423 protocol and the suppressive and curative murine malaria models, and to predict in silico the pharmacokinetic properties and drug-likeness of two major phytochemical constituents. The in vivo antimalarial efficacy was assessed using the P. berghei NK65-infected mice. The TiH2O treatment impact on biochemical parameters was measured using established standard procedures. The pharmacokinetics prediction was achieved through the pkCSM predictor and Swiss ADME. The TiH2O extract was nontoxic in BALB/c mice at a lethal dose of 50 (LD50) &gt; 2000 mg/kg. The TiH2O extract displayed strong antimalarial efficacy with 100% parasitemia suppression at 200 mg/kg b.w. after 4 days of treatment while its oral administration at 400 mg/kg b.w. in the curative model significantly decreased P. berghei parasitemia by 94.07% with a median efficacy dose (ED50) of 96.80 mg/kg. The administration of TiH2O extract restored the histological parameters disrupted by P. berghei, and the transaminase (ALT and AST) activity, creatinine, and bilirubin levels significantly decreased compared to the negative control mice. In silico explorations showed that the main constituents leucodelphidin (leucodelphinidin) and ellagic acid of the TiH2O extract have drug-like properties, thus indicating that T. ivorensis might constitute a promising source of antimalarial chemical entities with good pharmacokinetics and drug-like properties. The results obtained further corroborated the preliminary in vitro antiplasmodial studies of T. ivorensis stem bark aqueous extract. The metabolome of TiH2O extract should be further profiled in the prospects of characterizing novel natural product scaffolds to support antimalarial drug discovery.

Evaluation of antiplasmodial effects of black seeds, fenugreek and coriander seeds in albino mice infected with &lt;i&gt;Plasmodium berghei.&lt;/i&gt;

Malaria remains a disease of public concern according to reports by the World Health Organization which recommends diverse therapeutic approach including the use of plant derived products to combat drug resistance in malaria treated individuals. This study therefore, evaluates the antiplasmodial effects of black seeds (Nigella sativa), fenugreek (Trigonella foenum-graecum) and coriander seeds (Coriandrum sativum) and their effects on packed cell volume and weight of experimental mice. Phytochemical analysis of the extract was conducted using Gas Chromatography-Mass Spectrometry analysis to establish the presence of antimalarial constituents. The plant extracts were screened for curative activities at dosages of 50mg/kg, 100mg/kg and 200mg/kg, in mice inoculated with Plasmodium berghei from donor mice. Chloroquine (6mg/kg body weight) was used as standard control drug. A 4-day curative assay was used to evaluate the antimalarial potentials of the plant extracts. Comparison between treated samples were analyzed using single factor analysis of variance at 95% confidence interval and 5% significance level (P&lt;0.05). The results obtained from this study revealed significant suppression rate at 50mg/kg for Nigella sativa (67.0%), 200mg/kg for Trigonella foenum-graecum (68.3%), and 200mg/kg for Coriandrum sativum (66.7%). Chloroquine (6mg/kg) showed a higher inhibitory performance at 86.6% on day 7 post treatment compared to the plant extracts. The packed cell volume increased in groups treated with chloroquine compared to the extract treated group while the weight of mice increased in all extract groups significantly compared to the chloroquine treated group. The results of the study were statistically significant at P&lt;0.05.

A pH Fingerprint Assay to Identify Inhibitors of Multiple Validated and Potential Antimalarial Drug Targets.

New drugs with novel modes of action are needed to safeguard malaria treatment. In recent years, millions of compounds have been tested for their ability to inhibit the growth of asexual blood-stage Plasmodium falciparum parasites, resulting in the identification of thousands of compounds with antiplasmodial activity. Determining the mechanisms of action of antiplasmodial compounds informs their further development, but remains challenging. A relatively high proportion of compounds identified as killing asexual blood-stage parasites show evidence of targeting the parasite's plasma membrane Na+-extruding, H+-importing pump, PfATP4. Inhibitors of PfATP4 give rise to characteristic changes in the parasite's internal [Na+] and pH. Here, we designed a "pH fingerprint" assay that robustly identifies PfATP4 inhibitors while simultaneously allowing the detection of (and discrimination between) inhibitors of the lactate:H+ transporter PfFNT, which is a validated antimalarial drug target, and the V-type H+ ATPase, which was suggested as a possible target of the clinical candidate ZY19489. In our pH fingerprint assays and subsequent secondary assays, ZY19489 did not show evidence for the inhibition of pH regulation by the V-type H+ ATPase, suggesting that it has a different mode of action in the parasite. The pH fingerprint assay also has the potential to identify protonophores, inhibitors of the acid-loading Cl- transporter(s) (for which the molecular identity(ies) remain elusive), and compounds that act through inhibition of either the glucose transporter PfHT or glycolysis. The pH fingerprint assay therefore provides an efficient starting point to match a proportion of antiplasmodial compounds with their mechanisms of action.

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.

Describing the ligandin properties of Plasmodium falciparum and vivax glutathione transferase towards bromosulfophthalein from empirical and computational modelling viewpoints

Research has spotlighted glutathione transferase (GST) as a promising target for antimalarial drug development due to its pivotal role in cellular processes, including metabolizing toxins and managing oxidative stress. This interest arises from GST’s potential to combat multidrug resistance in existing antimalarial drugs. Plasmodium falciparum GST (PfGST) and Plasmodium vivax GST (PvGST) are key targets; inhibiting them not only disrupt detoxification but also reduce their antioxidant capacity, a critical feature for potent antimalarials. Bromosulfophthalein (BSP), a clinical liver function dye, emerged as a potent cytosolic GST inhibitor. This study explored BSP’s inhibitory properties on PfGST and PvGST, showcasing its binding capabilities through empirical and computational analyses. The study revealed BSP’s ability to significantly inhibit GST activity, altering the proteins’ structures and stability. Specifically, BSP binding induced spectral changes and impacted the proteins’ thermal stability, reducing their melting temperatures. Computational simulations highlighted BSP's strong binding to PfGST and PvGST at their dimer interface, stabilized by various interactions, including hydrogen bonds and van der Waals forces. Notably, BSP’s binding altered the proteins’ compactness and conformational dynamics, suggesting a potential non-competitive, allosteric inhibition mechanism. This study provided novel insights into BSP’s candidacy as an antimalarial drug by targeting PfGST and PvGST. Its ability to disrupt crucial functions of these enzymes’ positions BSP as a promising candidate for further drug development in combating malaria Communicated by Ramaswamy H. Sarma

Preliminary insight on diarylpentanoids as potential antimalarials: In silico, in vitro pLDH and in vivo zebrafish toxicity assessment

Malaria remains a major public health problem worldwide, including in Southeast Asia. Chemotherapeutic agents such as chloroquine (CQ) are effective, but problems with drug resistance and toxicity have necessitated a continuous search for new effective antimalarial agents. Here we report on a virtual screening of ∼300 diarylpentanoids and derivatives, in search of potential Plasmodium falciparum lactate dehydrogenase (PfLDH) inhibitors with acceptable drug-like properties. Several molecules with binding affinities comparable to CQ were chosen for in vitro validation of antimalarial efficacy. Among them, MS33A, MS33C and MS34C are the most promising against CQ-sensitive (3D7) with EC50 values of 1.6, 2.5 and 3.1 μM, respectively. Meanwhile, MS87 (EC50 of 1.85 μM) shown the most active against the CQ-resistant Gombak A strain, and MS33A and MS33C the most effective P. knowlesi inhibitors (EC50 of 3.6 and 5.1 μM, respectively). The in vitro cytotoxicity of selected diarylpentanoids (MS33A, MS33C, MS34C and MS87) was tested on Vero mammalian cells to evaluate parasite selectivity (SI), showing moderate to low cytotoxicity (CC50 > 82 μM). In addition, MS87 exhibited a high SI and the lowest resistance index (RI), suggesting that MS87 may exert effective parasite inhibition with low resistance potential in the CQ-resistant P. falciparum strain. Furthermore, the in vivo toxicity of the molecules on early embryonic development, the cardiovascular system, heart rate, motor activity and apoptosis were assessed in a zebrafish animal model. The overall results indicate the preliminary potential of diarylpentanoids, which need further investigation for their development as new antimalarial agents.