Plasmodium Strains Research Articles

CYP3A4-mediated metabolism of artemisinin to 10β-hydroxyartemisinin with comparable anti-malarial potency.

The most widely used anti-malarial drug artemisinin (ART) is metabolized extensively, but the therapeutic capacity of its major metabolite remains unknown. Whether the major metabolite of ART (ART-M) contributes to its antiplasmodial potency was investigated in this study. The metabolite identification and enzyme phenotyping of ART were performed using human liver microsomes (HLMs). The stereostructure of the major metabolite ART-M was elucidated by spectroscopic and X-ray crystallographic analysis. The anti-malarial activity of ART-M against two reference Plasmodium strains (Pf3D7 and PfDd2) was evaluated. The pharmacokinetic profiles of ART and its metabolite ART-M were investigated in healthy Chinese subjects after a recommended two-day oral dose of ART plus piperaquine. Pharmacodynamic parameters based on minimum inhibitory concentration (MIC50) and free plasma concentration were employed to evaluate the therapeutic potency of ART-M, including fAUC0-t/MIC50, fCmax/MIC50 and T > MIC50. A major metabolite 10β-hydroxyartemisinin (ART-M) was found for ART in human, and CYP3A4/3A5 was the major enzymes responsible for ART 10β-hydroxylation. Compared with ART (MIC50, 10.1nM against Pf3D7), weaker antiplasmodial activity was found for ART-M (MIC50, 61.4nM against Pf3D7). However, a 3.5-fold higher maximal free plasma concentration was achieved for ART-M (fCmax, 180.0nM vs. 51.8nM for ART). ART-M displayed comparable antiplasmodial potency to ART, in terms of fAUC0-t/MIC50 (12.5h), fCmax/MIC50 (2.8) and T > MIC50 (5h). The major metabolite 10β-hydroxyartemisinin contributes to the antiplasmodial efficacy of ART, which should be considered when evaluation of ART dosing regimens and/or clinical outcomes.

Preparation and Evaluation of Stability and Acute Oral Toxicity of a Drug Delivery System Combining MIL‐100(Fe) with Chloroquine Phosphate

AbstractMetal‐organic framework materials (MOFs) are highly porous and are the subject of growing interest among scientists globally for their utilization in drug delivery. In this work, iron‐based metal‐organic frameworks (MOFs) MIL‐100(Fe) were synthesized by ultrasonic method and studied for the loading of the chloroquine phosphate (CQP). The CQP‐release behavior of the material was investigated in water media with various pH solutions of 1.2, 2, 4.5, and phosphate‐buffered saline (PBS) at temperatures of 25 °C to 45 °C. MIL‐100(Fe) material had a high surface area of up to 1080 m2/g and could completely release the CQP at a pH of 1.2 after 25 hours. At other pH conditions, the drug exhibited an initial rapid release, followed by a gradual slowdown, ultimately achieving complete release after 96 hours. The maximal loading capacity for the CQP by the MIL‐100(Fe) was determined to be approximately 30 % at the pH solution of 2 (stomach environment). The findings from the activity assessment against the K1 malaria parasite strain (P. falciparum) indicated that the concentration at which the active ingredient, when carried by the material, exhibited inhibition was 193 nM/L. The evaluation outcomes for acute toxicity of the drug carrier material revealed an LD50 value exceeding 5000 mg/kg (equivalent to 1500 mg of CQP base). In contrast, when using the active substance alone, acute toxicity resulted in an LD50 value of 675 mg/kg.

Antimalarial Mechanisms and Resistance Status of Artemisinin and Its Derivatives.

Artemisinin is an endoperoxide sesquiterpene lactone isolated from Artemisia annua and is often used to treat malaria. Artemisinin's peroxide bridge is the key structure behind its antimalarial action. Scientists have created dihydroartemisinin, artemether, artesunate, and other derivatives preserving artemisinin's peroxide bridge to increase its clinical utility value. Artemisinin compounds exhibit excellent efficacy, quick action, and minimal toxicity in malaria treatment and have greatly contributed to malaria control. With the wide and unreasonable application of artemisinin-based medicines, malaria parasites have developed artemisinin resistance, making malaria prevention and control increasingly challenging. Artemisinin-resistant Plasmodium strains have been found in many countries and regions. The mechanisms of antimalarials and artemisinin resistance are not well understood, making malaria prevention and control a serious challenge. Understanding the antimalarial and resistance mechanisms of artemisinin drugs helps develop novel antimalarials and guides the rational application of antimalarials to avoid the spread of resistance, which is conducive to malaria control and elimination efforts. This review will discuss the antimalarial mechanisms and resistance status of artemisinin and its derivatives, which will provide a reference for avoiding drug resistance and the research and development of new antimalarial drugs.

Advances and Challenges for the Malaria Vaccine: A Review

Malaria remains a leading cause of morbidity and mortality worldwide, particularly in sub-Saharan Africa and Southeast Asia, where transmission rates are highest. Traditional control measures, such as insecticide-treated bed nets and antimalarial drugs, have helped reduce the disease’s impact, but challenges such as drug and insecticide resistance continue to undermine these efforts. A highly effective malaria vaccine represents a crucial step towards achieving long-term control and eventual eradication. This review explores recent advances in malaria vaccine development, including the RTS, S/AS01 and R21/Matrix-M vaccines, while highlighting their limitations related to efficacy, immunity duration, and accessibility in resource-poor regions. Additionally, it addresses the challenges in developing multivalent vaccines, targeting different strains of Plasmodium, and the need for integrated approaches combining vaccination with existing control strategies. Looking ahead, the review discusses the potential of next-generation vaccines, mRNA platforms, and hybrid strategies that could enhance global malaria control efforts. Keywords: Malaria vaccine, RTS, S/AS01, R21/Matrix-M, transmission-blocking vaccines, malaria control.

NDV targets the invasion pathway in malaria parasite through cell surface sialic acid interaction.

Merozoites utilize sialic acids on the red blood cell (RBC) cell surface to rapidly adhere to and invade the RBCs. Newcastle disease virus (NDV) displays a strong affinity toward membrane-bound sialic acids. Incubation of NDV with the malaria parasites dose-dependently reduces its cellular viability. The antiplasmodial activity of NDV is specific, as incubation with Japanese encephalitis virus, duck enteritis virus, infectious bronchitis virus, and influenza virus did not affect the parasite propagation. Interestingly, NDV is reducing more than 80% invasion when RBCs are pretreated with the virus. Removal of the RBC surface proteins or the NDV coat proteins results in disruption of the virus binding to RBC. It suggests the involvement of specific protein: ligand interaction in virus binding. We established that the virus engages with the parasitized RBCs (PRBCs) through its hemagglutinin neuraminidase (HN) protein by recognizing sialic acid-containing glycoproteins on the cell surface. Blocking of the HN protein with free sialic acid or anti-HN antibodies abolished the virus binding as well as its ability to reduce parasite growth. Interestingly, the purified HN from the virus alone could inhibit the parasite's growth in a dose-dependent manner. NDV binds strongly to knobless murine parasite strain Plasmodium yoelii and restricted the parasite growth in mice. Furthermore, the virus was found to preferentially target the PRBCs compared to normal erythrocytes. Immunolocalization studies reveal that NDV is localized on the plasma membrane as well as weakly inside the PRBC. NDV causes neither any infection nor aggregation of the human RBCs. Our findings suggest that NDV is a potential candidate for developing targeted drug delivery platforms for the Plasmodium-infected RBCs.

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.

Exploring the Recent Pioneering Developments of Small Molecules in Antimalarial Drug Armamentarium: A Chemistry Prospective Appraisal.

Malaria is a very destructive and lethal parasitic disease that causes significant mortality worldwide, resulting in the loss of millions of lives annually. It is an infectious disease transmitted by mosquitoes, which is caused by different species of the parasite protozoan belonging to the genus Plasmodium. The uncontrolled intake of antimalarial drugs often employed in clinical settings has resulted in the emergence of numerous strains of plasmodium that are resistant to these drugs, including multidrug-resistant strains. This resistance significantly diminishes the effectiveness of many primary drugs used in the treatment of malaria. Hence, there is an urgent need for developing unique classes of antimalarial drugs that function with distinct mechanisms of action. In this context, the design and development of hybrid compounds that combine pharmacophoric properties from different lead molecules into a single unit gives a unique perspective towards further development of malaria drugs in the next generation. In recent years, the field of medicinal chemistry has made significant efforts resulting in the discovery and synthesis of numerous small novel compounds that exhibit potent antimalarial properties, while also demonstrating reduced toxicity and desirable efficacy. In light of this, we have reviewed the progress of hybrid antimalarial agents from 2021 up to the present. This manuscript presents a comprehensive overview of the latest advancements in the medicinal chemistry pertaining to small molecules, with a specific focus on their potential as antimalarial agents. As possible antimalarial drugs that might target both the dual stage and multi-stage stages of the parasite life cycle, these small hybrid molecules have been studied. This review explores a variety of physiologically active compounds that have been described in the literature in order to lay a strong foundation for the logical design and eventual identification of antimalarial drugs based on lead frameworks.

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.

The human malaria-Aotus monkey model: a historical perspective in antimalarial chemotherapy research at the Gorgas Memorial Laboratory-Panama.

The human malaria-Aotus monkey model has served the malaria research community since its inception in 1966 at the Gorgas Memorial Laboratory (GML) in Panama. Spanning over five decades, this model has been instrumental in evaluating the in vivo efficacy and pharmacokinetics of a wide array of candidate antimalarial drugs, whether used singly or in combination. The animal model could be infected with drug-resistant and susceptible Plasmodium falciparum and Plasmodium vivax strains that follow a characteristic and reproducible course of infection, remarkably like human untreated and treated infections. Over the years, the model has enabled the evaluation of several synthetic and semisynthetic endoperoxides, for instance, artelinic acid, artesunate, artemether, arteether, and artemisone. These compounds have been evaluated alone and in combination with long-acting partner drugs, commonly referred to as artemisinin-based combination therapies, which are recommended as first-line treatment against uncomplicated malaria. Further, the model has also supported the evaluation of the primaquine analog tafenoquine against blood stages of P. vivax, contributing to its progression to clinical trials and eventual approval. Besides, the P. falciparum/Aotus model at GML has also played a pivotal role in exploring the biology, immunology, and pathogenesis of malaria and in the characterization of drug-resistant P. falciparum and P. vivax strains. This minireview offers a historical overview of the most significant contributions made by the Panamanian owl monkey (Aotus lemurinus lemurinus) to malaria chemotherapy research.

Unlocking nitrogen compounds' promise against malaria: A comprehensive review.

Plasmodium parasites are the primary cause of malaria, leading to high mortality rates, which require clinical attention. Many of the medications used in the treatment have resulted in resistance over time. Artemisinin combination therapy (ACT) has shown significant results for the treatment. However, mutations in the parasite have resulted in resistance, leading to decreased efficiency of the medications that are currently being used. Therefore, there is a critical need to find novel scaffolds that are safe, effective, and of economic advantage. Literature has reported several potent molecules with diverse scaffolds designed, synthesized, and evaluated against different strains of Plasmodium. With this growing list of compounds, it is essential to collect the data in one place to gain a concise overview of the emerging scaffolds in recent years. For this purpose, nitrogen-containing heterocycles such as β-carboline, imidazole, quinazoline, quinoline, thiazole, and thiophene have been highly explored due to their wide biological applications. Besides these, another scaffold, benzodiazepine, which is majorly used as a central nervous system depressant, is emerging as an anti-malarial agent. Hence, this review centers on the latest medication advancements designed to combat malaria, emphasizing special attention to 1,4-benzodiazepines as a novel scaffold for antimalarial drug discovery.

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.

Cu-catalyzed click reaction in synthesis of eugenol derivatives as potent antimalarial agents

Eugenol(1), a terpenoid found in Ocimum, has various biological activities. The present study aims at extraction, isolation of the plant secondary metabolite eugenol (1), it’s derivatisation and structure identification as bioactive molecules. Synthesis and antiplasmodial activity (in-vitro and in-vivo), of a series of fourteen novel eugenol-based 1,2,3-triazole derivatives was done in the present study. Derivatives 5a–5n showed good antimalarial activity against the strain Plasmodium falciparum NF54. Derivative 5 m, IC50 at 2.85 µM was found to be several times better than its precursor 1 (106.82 µM) whereas the derivative 5n showed three fold better activity than compound 1, in vitro. The structure-activity relationship of the synthesised compounds indicated that the presence of triazole ring in eugenol analogues is responsible for their good activity. Compound 5m, was further evaluated for in-vivo antimalarial activity which showed about 79% parasitemia suppression. It is the first report on antimalarial activity of triazole eugenol derivatives.

Synthesis and biological evaluation of hydantoin derivatives as potent antiplasmodial agents

Malaria, a devastating disease, has claimed numerous lives and caused considerable suffering, with young children and pregnant women being the most severely affected group. However, the emergence of multidrug-resistant strains of Plasmodium and the adverse side effects associated with existing antimalarial drugs underscore the urgent need for the development of novel, well-tolerated, and more efficient drugs to combat this global health threat. To address these challenges, six new hydantoins derivatives were synthesized and evaluated for their in vitro antiplasmodial activity. Notably, compound 2c exhibited excellent inhibitory activity against the tested Pf3D7 strain, with an IC50 value of 3.97 ± 0.01 nM, three-fold better than chloroquine. Following closely, compound 3b demonstrated an IC50 value of 27.52 ± 3.37 µM against the Pf3D7 strain in vitro. Additionally, all the hydantoins derivatives tested showed inactive against human MCR-5 cells, with an IC50 value exceeding 100 μM. In summary, the hydantoin derivative 2c emerges as a promising candidate for further exploration as an antiplasmodial compound.

Antiplasmodial activity, in silico ADME and mammalian cell cytotoxicity of a synthetic protoberberine alkaloid, coralyne

Coralyne is a synthetic protoberberine alkaloid with anticancer activity and selectivity superior to that of berberine, its congener. As berberine is gifted with antiplasmodial activity, this study assessed the antiplasmodial activity of coralyne against erythrocytic stages of the malaria parasite in culture. Parasites were cultured by adopting the method described by Trager and Jensen in 1976. Following this, parasites were exposed at ring stage to increasing doses of coralyne to enable us compute the IC50. Further, given that berberine is a substrate of the efflux transporter permeability glycoprotein (P-gp), in silico techniques were used to study the pharmacokinetics of oral coralyne. Coralyne showed excellent potency (IC50Pf3D7: 0.52 µg/ml) against chloroquine sensitive strain and a little less potency (IC50PfINDO: 1.15 µg/ml) against the chloroquine resistant malaria parasite strain (Resistance index: 2.21). Further, with CC50HEK: >100 µg/ml, it was non-toxic to mammalian cells. However, in silico absorption, distribution, metabolism and excretion (ADME) studies predicts that like berberine, coralyne may also have poor oral bioavailability thus limiting its usefulness as an orally deliverable antimalarial agent. Given the negative impact of low bioavailability in the development of protoberberine alkaloids as antimalarials, synthesizing analogues of coralyne with nanomolar potency against the malaria parasite and improved oral pharmacokinetics may be a good strategy for the future.

Bioguided antiplasmodial isolation of six new labdane-type diterpenoids from the stem bark of Croton sylvaticus Hochst. Ex. Krauss

The CH2Cl2-MeOH (1:1, v/v) extract of Croton sylvaticus stem bark selectively exhibited good antiplasmodial activity during preliminary screening against the multidrug-resistant (Dd2) and chloroquine sensitive (3D7) strains of Plasmodium falciparum with IC50 values of 10.57 and 18.47 μg/mL, respectively. After fractionation, the fractions exhibited moderate to good activity with IC50 values ranging from 4.31 to 25.49 μg/mL. The purification of these fractions led to the isolation of six new labdane-type diterpenoids named sylvacrotonins AF (16), alongside seven known compounds (713). Their structures were determined based on the analysis of their NMR and MS data. The isolated compounds were assessed in vitro for their antiplasmodial activity against Pf3D7 and PfDd2. The new labdane-type diterpenoids showed moderate antiplasmodial activity against the two P. falciparum strains, with compound 6 being the most active, with IC50 values of 11.26 and 21.80 μg/mL against PfDd2 and Pf3D7, respectively. Cytotoxic assays were performed on African green monkey kidney Vero cells to ensure that the obtained activity was specific to the parasites. Interestingly, all the tested extracts, fractions, and isolated compounds showed acceptable selectivity (SI > 10) against both Plasmodium strains, except fractions CSB-E (SI = 3.93) and CSB-C (SI = 9.22) against Pf3D7. Globally, with resistance indexes (RIs) lower than 1, all the tested samples were found to be more active against multidrug-resistant (PfDd2) than sensitive (Pf3D7) strains. Furthermore, all the isolated compounds exhibited cell cytotoxicity in the normal Vero cell line. The results from this study confirm the use of C. sylvaticus in malaria-endemic countries for its management and suggest that further lead-optimization studies on hit compounds could drive to the identification of potential lead molecules for antimalarial control and eradication.

Characterization of a nuclear transport factor 2-like domain-containing protein in Plasmodium berghei

BackgroundPlasmodium lacks an mRNA export receptor ortholog, such as yeast Mex67. Yeast Mex67 contains a nuclear transport factor 2 (NTF2)-like domain, suggesting that NTF2-like domain-containing proteins might be associated with mRNA export in Plasmodium. In this study, the relationship between mRNA export and an NTF2-like domain-containing protein, PBANKA_1019700, was investigated using the ANKA strain of rodent malaria parasite Plasmodium berghei.MethodsThe deletion mutant Δ1019700 was generated by introducing gene-targeting vectors into the P. berghei ANKA genome, and parasite growth and virulence were examined. To investigate whether PBANKA_1019700 is involved in mRNA export, live-cell fluorescence imaging and immunoprecipitation coupled to mass spectrometry (IP-MS) were performed using transgenic parasites expressing fusion proteins (1019700::mCherry).ResultsDeletion of PBANKA_1019700 affected the sexual phase but not the asexual phase of malaria parasites. Live-cell fluorescence imaging showed that PBANKA_1019700 localizes to the cytoplasm. Moreover, IP-MS analysis of 1019700::mCherry indicated that PBANKA_1019700 interacts with ubiquitin-related proteins but not nuclear proteins.ConclusionsPBANKA_1019700 is a noncanonical NTF2-like superfamily protein.

Designing novel anti-plasmodial quinoline-furanone hybrids: computational insights, synthesis, and biological evaluation targeting Plasmodium falciparum lactate dehydrogenase.

To combat resistance against current antimalarials, modifying key pharmacophores and exploring novel parasite-specific drug targets remained one of the key drug design strategies. The resistance to quinoline-based antimalarials arises often due to the efflux of the drug. Hence, the development of newer agents containing bulkier pharmacophores will enable medicinal chemists to counteract drug resistance. In view of this, herein we designed bulkier quinoline-furanone hybrids. Initially, virtual drug-likeness and ADMET screening were conducted to optimize physicochemical properties followed by docking of the hybrids against the Plasmodium falciparum lactate dehydrogenase (PfLDH) enzyme. The most potent hybrids that emerged from the computational screening were synthesized and screened for their bioactivity against the resistant strain of Plasmodium through Schizont Maturation Inhibition assays. Among the compounds tested, 5g and 6e demonstrated the best activity, with IC50 values similar to chloroquine (CQ), and 5g exhibited superior LDH inhibition compared to CQ. Compounds 5f, 7a, and 7f showed IC50 values comparable to CQ and moderate LDH inhibition. Structure-activity relationship (SAR) analysis revealed that halogen substitutions, particularly Br and Cl, enhanced antimalarial activity, while strong electron-withdrawing (-NO2) or -donating (-OH) groups led to diminished activity. Additionally, bulkier aromatic substitutions were favoured for antimalarial activity and LDH inhibition. The investigation successfully found potent anti-plasmodial quinoline-furanone hybrids, demonstrating promising prospects for combating malaria.

Antimalarial evaluation of alkyl-linked bis-thiadiazine derivatives in murine model infected with two Plasmodium strains.

Plasmodium falciparum and P. vivax are responsible for most malaria cases in humans in the African Region and the Americas; these parasites have developed resistance to classic antimalarial drugs. On the other hand, previous investigations of the alkyl-linked bis tetrahydro-(2H)-1,3,5-thiadiazine-2-thione (bis-THTT) derivatives compounds show satisfactory results against protozoan parasites such as Trypanosoma cruzi, Trypanosoma vaginalis, Trypanosoma brucei rhodesiense and Leishmania donovani. Therefore, it is possible to see some effect of bis-THTT derivatives on other protozoan parasites, such as Plasmodium. This study aimed to perform an in vivo biological evaluation of bis-THTT (JH1 to JH6) derivatives compounds as possible anti-malaria drugs in BALB/c mice infected with Plasmodium berghei ANKA and Plasmodium yoelii 17XL strains. In this work, we evaluated the compounds as potential antimalarial drugs in BALB/c mice infected with Plasmodium strains. For each compound, we assess the percentages of parasitemia by smears from tail blood and the humoral response by indirect ELISA test using each compound as an antigen. We also evaluated the B lymphocyte response and the cytotoxicity of the bis-THTT derivatives compounds with MTT cell proliferation assays. Our results show that the bis-THTT derivatives JH2 and JH4 presented effective parasitemia control in mice infected with P. berghei; JH5 and JH6 compounds have similar infection control results as chloroquine in mice infected P. yoelii strain. The evaluation of bis-THTT derivatives compounds in a model of BALB/c mice infected with P. berghei and P. yoelii allowed us to conclude that some of them have an antimalarial effect; however, none of the tested compounds exceeded the efficiency of chloroquine.

The antiplasmodial activity of the carboxylic acid metabolite of piperaquine and its pharmacokinetic profiles in healthy volunteers.

The long-acting antimalarial drug piperaquine can be metabolized into the carboxylic acid metabolite (PQM). However, the clinical relevance of PQM remains unclear. The pharmacodynamics/pharmacokinetics of PQM were studied. The antimalarial activity of PQM was studied in vitro (Plasmodium strains Pf3D7 and PfDd2) and in vivo (murine Plasmodium yoelii). The toxicity of PQM was evaluated in mice, in terms of the general measures of animal well-being, serum biochemical examination and ECG monitoring. The pharmacokinetic profiles of piperaquine and its metabolite PQM were investigated in healthy subjects after recommended oral doses of piperaquine. PQM showed no relevant in vitro antimalarial activity (IC50 > 1.0 μM) with no significant toxicity. After recommended oral administration of piperaquine to healthy subjects, the maximum concentration of PQM was less than 30.0 nM, and it did not accumulate after repeated dosing. With a low antimalarial potency, PQM should not contribute to the efficacy of piperaquine with clinically acceptable doses.

Molecular surveillance of chloroquine resistance in Plasmodium vivax isolates from malaria cases in Yunnan Province of China using pvcrt-o gene polymorphisms

BackgroundThe efficacy of chloroquine treatment for vivax malaria has been rarely evaluated due to a lack of an appropriate testing method. The objective of this study was to conduct molecular monitoring of chloroquine resistance in Plasmodium vivax strains from vivax malaria patients in Yunnan Province, focusing on the analysis of polymorphism in the P. vivax chloroquine resistance transporter protein orthologous gene (pvcrt-o).MethodsIn accordance with the principles of a cohort study, blood samples were collected from malaria cases diagnosed with a P. vivax mono-infection in Yunnan Province from 2020 to 2022. Segmental PCR was used to amplify the whole pvcrt-o gene in the blood samples and their products were subsequently sequenced. The sequencing data were arranged to obtain the full coding DNA sequence (CDS) as well as the gene’s promoter region sequences. The CDSs were aligned with the reference sequence (XM_001613407.1) of the P. vivax SalI isolate to identify the mutant loci.ResultsFrom a total of 375 blood samples taken from vivax malaria cases, 272 both whole gene CDSs (1272–1275 bp) and promoter DNA sequences (707 bp) of pvcrt-o gene were obtained. Among the whole CDSs, there were 7 single nucleotide polymorphic sites in which c.7 A>G was the minor allele frequency (MAF) site with 4.4% (12/272) detection rate. The mutation detection rate showed a significant decrease from 9.8% (10/102) in 2020 to 1.1% (1/92) in 2021 and 1.3% (1/78) in 2022, indicating statistical significance (χ2 = 11.256, P < 0.05). Among the identified 12 haplotypes, the majority of which were wild type (75.7%; 206/272). These four mutant haplotypes (Hap_3, Hap_5, Hap_9, and Hap_10) were classified as “K10 insertion type” and accounted for 12.1% (33/272). The detection rate of Hap_3 increased from 1.0% (1/102) in 2020 to 13.0% (12/92) in 2021 and 14.1% (11/78) in 2022, indicating statistical significance. A total of 23.8% (65/272) of the samples exhibited 14 bp (bp) deletions in the promoter region, occurring most frequently in the wild type haplotype (Hap_1) samples at a rate of 28.6% (59/206).ConclusionsIn recent years in Yunnan Province, a notable proportion of vivax malaria patients are infected by P. vivax strains with a “K10 insertion” and partial sequence deletions in the promoter region of the pvcrt-o gene, necessitating vigilance.