The Plasmodium falciparum protein PfMRP1 functions as an influx ABC transporter

Adenosine triphosphate (ATP)-binding cassette (ABC) transporters play an important role in mediating solute or drug transport across cellular membranes. Although this class of transporters has been well characterized in diverse organisms little is known about the physiological roles in Plasmodium falciparum, the deadliest malaria parasite species. We studied the Plasmodium falciparum Multidrug Resistance-associated Protein 1 (PfMRP1; PF3D7_0112200), an ABC transporter localized to the parasite plasma membrane, generating genetic disrupted parasites. We demonstrate that parasites with disrupted pfmrp1 are resistant to folate analogs, methotrexate and aminopterin, with antimalarial activity. This phenotype occurs due to reduction in compound accumulation in the parasite cytoplasm. Phylogenetic analysis supports pfmrp1 being distantly related to ABC transporters in other eukaryotes, suggesting an unusual function. We propose that PfMRP1 can act as a solute importer, a function not previously observed in this organism.

A Novel 2-Carbon-Linked Dimeric Artemisinin With Potent Antileukemic Activity and Favorable Pharmacology

Acute myeloid leukemia (AML) remains a devastating disease, with low cure rates despite intensive standard chemotherapy regimens. In the past decade, targeted antileukemic drugs have emerged from research efforts. Nevertheless, targeted therapies are often effective for only a subset of patients whose leukemias harbor a distinct mutational or gene expression profile and provide only transient antileukemic responses as monotherapies. We previously presented single agent and combination preclinical data for a novel 3-carbon-linked artemisinin-derived dimer (3C-ART), diphenylphosphate analog 838 (ART838), that indicates a promising approach to treat AML, given its demonstrated synergy with targeted antileukemic drugs and large therapeutic window. We now report new data from our initial evaluation of a structurally distinct class of 2-carbon-linked dimeric artemisinin-derived analogs (2C-ARTs) with prior documented in vivo antimalarial activity. These 2C-ARTs have antileukemic activity at low (nM) concentrations, have similar cooperativity with other antineoplastic drugs and comparable physicochemical properties to ART838, and provide a viable path to clinical development.

Microwave Irradiated Synthesis of Pyrimidine Containing, Thiazolidin-4-ones: Antimicrobial, Anti-tuberculosis, Antimalarial, and Anti-protozoa evaluation

Aim: This study aims to synthesize thiazolidine-4-one compounds with a pyrimidine nucleus and evaluate against different species of bacteria, fungi, protozoa, and the malaria parasite. Background: Microwave irradiation was the best method for synthesizing the thiazolidin-4-one ring system. It took only 15 minutes for synthesizing thiazolidin-4-one while the conventional method required 12 hours. The rapid reaction was the main concern of this research. Objective: Pyrimidine and Thiazolidin-4-one nucleus have broad-spectrum biological activity and when it is introduced with other hetero atoms containing moiety, many types of biological activities have been found; antimicrobial, anti-tuberculosis, anti-protozoa, antimalarial are the main activities. The activity of these compounds inspired us to do extra research on Thiazolidin-4-one fused pyrimidines with different functional groups. The aim of this is to synthesize a combination of these two ring systems in less time by using a microwave irradiation method and to evaluate new compounds for different bioactivity. Method: 2-(4-Chlorophenyl)-3-(4-(substituted phenyl)-6-(substituted aryl) pyrimidin-2-yl) thiazolidin-4-ones (6A-J) were synthesized by microwave irradiation to save energy and time. The structure of all newly synthesized motifs was characterized by spectral analysis (1H NMR, 13C NMR, IR, spectroscopy) and screened for antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pyogenes, antifungal activity against Candida albicans, Aspergillus niger, Aspergillus clavatus, anti-tuberculosis activity against M. tuberculosis H37RV, antimalarial activity against Plasmodium falciparum and anti-protozoa activity against L. mexicana and T. cruzi. Result: Because of microwave irradiation synthesis, time period is very less for preparing the new compound. Biological response given by compounds 6B, 6C, 6D, 6E, 6G, 6H, and 6J was found excellent. Conclusion: Good yield with purity of the newly synthesized thiazolidine-4-one compounds obtained in less time by using microwave irradiation. The biological response of some of the compounds of this series was found excellent

DNA binding by the antimalarial compound artemisinin

Artemisinin (ART) is a vital medicinal compound that is used alone or as part of a combination therapy against malaria. ART is thought to function by attaching to heme covalently and alkylating a range of proteins. Using a combination of biophysical methods, we demonstrate that ART is bound by three-way junction and duplex containing DNA molecules. Binding of ART by DNA is first shown for the cocaine-binding DNA aptamer and extensively studied using this DNA molecule. Isothermal titration calorimetry methods show that the binding of ART is both entropically and enthalpically driven at physiological NaCl concentration. Native mass spectrometry methods confirm DNA binding and show that a non-covalent complex is formed. Nuclear magnetic resonance spectroscopy shows that ART binds at the three-way junction of the cocaine-binding aptamer, and that binding results in the folding of the structure-switching variant of this aptamer. This structure-switching ability was exploited using the photochrome aptamer switch assay to demonstrate that ART can be detected using this biosensing assay. This study is the first to demonstrate the DNA binding ability of ART and should lay the foundation for further work to study implications of DNA binding for the antimalarial activity of ART.

Antimalarial Activity of Ethanol Extract of Kelakai Leaves (Stenochlaena palustris) to Parasitemia and Splenomegaly in BALB/c Mice Infected with Plasmodium berghei ANKA

Introduction: Malaria is one of global health problems. Splenomegaly is one of malaria symptoms. Antimalarial drug resistance had been reported. Alternative treatment is by using traditional medicinal plants such as kelakai (Stenochlaena palustris). Kelakai contains alkaloid and flavonoid which had been reported to have antimalarial activity. The aim of this study was to discover antimalarial activity of ethanol extract of kelakai leaves to parasitemia and splenomegaly of Plasmodium berghei ANKA in infected BALB/c mice.Methods: This study was based on a modified Peter test using BALB/c mice infected with P. berghei ANKA treated with ethanol extract of kelakai leaves, with chloroquine diphosphate as a positive control. The negative control was P. berghei ANKA infected mice without any additional treatment. Administration of ethanol extract of kelakai leaves was performed for 4 days with a serial doses of 100, 10, and 1 mg/kg body weight. The positive control was given chloroquine diphosphate 20 mg/kg body weight. Parasitemia was observed daily prior to the calculation of the percentage of parasite growth and parasite growth inhibition. At the end of the test, the mice were sacrificed and spleens were isolated to measure their sizes. Probit analysis was performed to obtain ED50 to find the effect of extract in parasite killing by 50%. Spearman test was performed to analyze the correlation of doses of extract and splenomegaly.Results: Parasitemia growth inhibition was directly proportional to the dose. Higher parasitemia inhibition was obtained at higher doses and vice versa. Result of probit analysis showed an ED50 was 77.05 mg/kg body weight. Statistical analysis resulted in insignificant correlation between doses and splenomegaly p = 1.0 (significancy < 0.05).Conclusion: Ethanol extract of kelakai leaves possessed good antimalarial activity and there was no correlation between extract doses and splenomegaly in Plasmodium berghei ANKA-infected mice.

The Role of the Iron Protoporphyrins Heme and Hematin in the Antimalarial Activity of Endoperoxide Drugs

Plasmodium has evolved to regulate the levels and oxidative states of iron protoporphyrin IX (Fe-PPIX). Antimalarial endoperoxides such as 1,2,4-trioxane artemisinin and 1,2,4-trioxolane arterolane undergo a bioreductive activation step mediated by heme (FeII-PPIX) but not by hematin (FeIII-PPIX), leading to the generation of a radical species. This can alkylate proteins vital for parasite survival and alkylate heme into hematin–drug adducts. Heme alkylation is abundant and accompanied by interconversion from the ferrous to the ferric state, which may induce an imbalance in the iron redox homeostasis. In addition to this, hematin–artemisinin adducts antagonize the spontaneous biomineralization of hematin into hemozoin crystals, differing strikingly from artemisinins, which do not directly suppress hematin biomineralization. These hematin–drug adducts, despite being devoid of the peroxide bond required for radical-induced alkylation, are powerful antiplasmodial agents. This review addresses our current understanding of Fe-PPIX as a bioreductive activator and molecular target. A compelling pharmacological model is that by alkylating heme, endoperoxide drugs can cause an imbalance in the iron homeostasis and that the hematin–drug adducts formed have strong cytocidal effects by possibly reproducing some of the toxifying effects of free Fe-PPIX. The antiplasmodial phenotype and the mode of action of hematin–drug adducts open new possibilities for reconciliating the mechanism of endoperoxide drugs and for malaria intervention.

Assessment in vitro of the antimalarial and transmission blocking activities of Cipargamin and Ganaplacide in artemisinin resistant Plasmodium falciparum

Artemisinin resistance in Plasmodium falciparum has emerged and spread widely in the Greater Mekong Subregion threatening current first line artemisinin combination treatments. New antimalarial drugs are needed urgently. Cipargamin (KAE609) and ganaplacide (KAF156) are promising novel antimalarial compounds in advanced stages of development. Both compounds have potent asexual blood stage activities, inhibit P. falciparum gametocytogenesis and reduce oocyst development in anopheline mosquitoes. In this study, we compared the asexual and sexual stage activities of cipargamin, ganaplacide and artesunate in artemisinin resistant P. falciparum isolates (N=7, K13 mutation; C580Y, G449A and R539T) from Thailand and Cambodia. Asexual blood stage antimalarial activity was evaluated in a SYBR-green I based 72h in vitro assay, and the effects on male and female mature stage V gametocytes were assessed in the P. falciparum dual gamete formation assay. Ganaplacide had higher activities when compared to cipargamin and artesunate, with a mean (SD) IC50 against asexual stages of 5.5 (1.1) nM, 7.8 (3.9) nM for male gametocytes and 57.9 (59.6) nM for female gametocytes. Cipargamin had a similar potency against male and female gametocytes, with a mean (SD) IC50 of 123.1 (80.2) nM for male gametocytes, 88.5 (52.7) nM for female gametocytes and 2.4 (0.6) nM for asexual stages. Both cipargamin and ganaplacide showed significant transmission-blocking activities against artemisinin resistant P. falciparum in vitro .

THE METABOLITE FINGERPRINTS, ANTIMALARIAL ACTIVITIES AND TOXICITIES OF ARTOCARPUS CHAMPEDEN STEMBARK FROM VARIOUS REGIONS IN INDONESIA

In Indonesia, cempedak (Artocarpus champeden Spreng) stembark from family of moraceae had been traditionally used for malarial treatment. Difference in the location of growth could cause the difference of metabolite fingerprints. As a result, there might be different toxicity and antimalarial activity in the same plants. The goal of this study was to obtain the fingerprints of the metabolites found in A. champeden stembark from different parts of Indonesia in order to authenticate and control the extract's quality. Fingerprints were performed using the HPTLC-Densitometry technique, in vitro toxicity and antimalarial activity were also determined using MTT assay and HRP2 assay. The correlation between metabolite fingerprints, toxicity and antimalarial activity was analysed using chemometrics tools: Principle Component Analysis (PCA), Partial Least Square (PLS) and Hierarchical Clustering Analysis (HCA). As a result, there is significant difference between fingerprints and toxicity profiles of A. champeden (p<0.05), whereas for antimalarial profiles, there is no significant difference between of them (p>0.05). Meanwhile, the nutrients (copper, zinc and manganese) are suspected to be responsible for the metabolite content. Besides morachalcone-A, compounds with Rf values ​​of 0.66 and 0.63 can be proposed as additional markers because they have responsibility for antimalarial activity and toxicity.

Synthesis, Characterization and Evaluation of Biological Activities of Sn(II) Complexes of Schiff Base Incorporating Sulpha Drugs

In this study, we report synthesis, characterization and biological activities of four sulpha drug based Schiff base ligands and their Sn(II) complexes. The Schiff bases and their Sn(II) complexes have been synthesized by traditional methods and characterized by the spectral techniques IR, NMR (1H and 13C), mass and TGA-DTA. Newly synthesized Schiff bases (L1-L4) and their Sn(II) complexes (C-1 to C-4) have been screened for antibacterial activity against bacterial strains S. aureus, S. pyogenus, E. coli, P. aeruginosa and antifungal activity against fungal strains C. albicans, A. niger, A. clavatus using broth micro dilution method. Best antimicrobial activity was shown by C-3 complex against E. coli (MIC, 50.0 µg/mL) and A. niger microbial strains (MIC, 100 µg/mL). Moreover, antimalarial activity against plasmodium falciparum was also studied. Complex C-3 was found to be more active against parasite P. falciparum (IC50, 0.04 µg/mL). Results showed that dichloride tin complexes are more active with respect to their corresponding Schiff base ligands.