Chloroquine-resistant Plasmodium Research Articles

Frequency of chloroquine-resistant haplotype of Plasmodium falciparum (CVIET) in Ibadan, Southwest Nigeria 17 years post-chloroquine withdrawal

The replacement of chloroquine with artemisinin-based combination therapies (ACTs) for over a decade has had varying impacts on the ability of the malaria parasite to sustain its chloroquine resistance prowess in different malaria-endemic regions. We evaluated the frequency of Plasmodium falciparum chloroquine resistance transporter (PfCRT) mutations in Ibadan, Nigeria 17 years after the replacement of chloroquine with ACTs for malaria treatment. Fragments of PfCRT gene from genomic DNA of microscopically confirmed P. falciparum-infected patients were amplified and sequenced. There were 19% CVIET mutant and 81% CVMNK wild-type haplotypes on residues 72–76. A220S change were found in 16.7% of samples occurring concurrently with the CVIET haplotype, while a Q271E mutation occurred in a PfCRT wild-type isolate. The reduced prevalence of the PfCRT mutant alleles in this study compared to previous reports suggests a gradual disappearance of chloroquine-resistant malaria parasites following reduced drug pressure. It may also be a result of fitness demand on the parasites in attempts to evolve resistance against the current first-line regimen. However, evaluating the prevalence of other chloroquine resistance markers such as Plasmodium falciparum multidrug resistance 1 gene mutations in this population, and a more robust sample size will help to consolidate these findings.

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.

New antiplasmodial piperazine alkaloid derivatives from Rauvolfia mannii Stapf. (Apocynaceae)

The stem bark extract of Rauvolfia mannii (Apocynaceae) was submitted to chemical and antiparasitic investigations. Chemical analyses resulted in the isolation of two new furyl-piperazine alkaloid derivatives namely 2-(2″-hydroxymethylhexyloxy)furan-5′-yl)-6-(piperazin-7-yl)piperazine (1) and 2-(2″-methylhexyloxy)furan-5′-yl)-6-(piperazin-7-yl)piperazine (2), along with six known compounds. The structures (including the relative stereochemistry) of these secondary metabolites were determined based on spectroscopic data, chemical correlations and comparison with the literature data. 1 and 2 display at least one piperazine ring, hence induce Rauvolfia alkaloids bearing rare skeletons. They are in fact, reported for the first time from the Apocynaceae family. Additionally, two of the isolates, arjunolic acid (5) and echitamine (7) showed moderate antiplasmodial activity against the chloroquine resistant (CQR) Plasmodium falciparum Dd2 with IC50 values of 22.5 and 16.3 μg/mL respectively.

Evaluating phytochemical constituents and in-vitro antiplasmodial and antioxidant activities of Fadogiella stigmatoloba, Hygrophylla auriculata, Hylodesmum repandum, and Porphyrostemma chevalieri extracts

IntroductionFadogiella stigmatoloba, Hygrophylla auriculata, Hylodesmum repandum and Porphyrostemma chevalieri are used against malaria in traditional medicine in the Democratic Republic of the Congo (DRC). To evaluate their potential in the treatment of this disease, the in vitro antiplasmodial property of these four plants was evaluated. All experiments were conducted on methanolic extracts performed on selected organ parts of these plants. MethodsThe methanolic extracts, obtained by maceration, were firstly screened in vitro against the chloroquine sensitive (3D7) and resistant (W2) Plasmodium falciparum strains by the measurement of lactate dehydrogenase activity, and on human keratinocytes (HaCat) cells by the MTT assay to determine their selectivity indices (SI). Secondly, the antioxidant activity of the same extracts was evaluated using DPPH and FRAP assays. Finally, the presence of specific phytochemical constituents was evaluated using standard methods and tentatively identified by GC-MS. ResultsAn optimum antiplasmodial activity (IC50 = 3.4 ± 0.7 μg/mL, for 3D7, SI = 58.2; IC50 = 7 ± 1.0 μg/mL, for W2, SI = 28.3) was obtained with the leave extract of P. chevalieri. The leaves (for F. stigmatoloba and H. repandum), and the aerial part (for H. repandum) extracts showed promising and moderate antiplasmodial activities against respectively the 3D7 strain (IC50: <15 μg/mL), and W2 strain (IC50:15–50 μg/mL). All extracts presented a weak cytotoxic effect (IC50: >100 μg/mL) on HaCat cells. For the antioxidant test, the most interesting activity was obtained with the leaf extract of P. chevalieri. The GC–MS analysis of these four plants species extracts revealed the presence of various compounds, such as Ethyl 2-nonenoate, 2-(2-Hydroxy-2-phenylethyl)-3,5,6-trimethyl pyrazine, Palmitic Acid, Ethyl palmitate, Ethyl linolenate, and N-Acetyltyramine. ConclusionBased on the obtained results, P. chevalieri could be selected for further investigations or ⁄and for the management of malaria after standardization.

Bioguided Fractionation and Isolation of an Antiplasmodial Saponin from the Roots of Nauclea xanthoxylon (A.Chev.) Aubrév. (Rubiaceae).

The root extract of Nauclea xanthoxylon (A.Chev.) Aubrév. displayed significant 50 % inhibition concentration (IC50 s) of 0.57 and 1.26 μg/mL against chloroquine resistant and sensitive Plasmodium falciparum (Pf) Dd2 and 3D7 strains, respectively. Bio-guided fractionation led to an ethyl acetate fraction with IC50 s of 2.68 and 1.85 μg/mL and subsequently, to the new quinovic acid saponin named xanthoxyloside (1) with IC50 s of 0.33 and 1.30 μM, respectively against the tested strains. Further compounds obtained from ethyl acetate and hexane fractions were the known clethric acid (2), ursolic acid (3), quafrinoic acid (4), quinovic acid (5), quinovic acid 3-O-β-D-fucopyranoside (6), oleanolic acid (7), oleanolic acid 3-acetate (8), friedelin (9), β-sitosterol (10a), stigmasterol (10b) and stigmasterol 3-O-β-D-glucopyranoside (11). Their structures were characterised with the aid of comprehensive spectroscopic methods (1 and 2D NMR, Mass). Bio-assays were performed using nucleic acid gel stain (SYBR green I)-based fluorescence assay with chloroquine as reference. Extracts and compounds exhibited good selectivity indices (SIs) of >10. Significant antiplasmodial activities measured for the crude extract, the ethyl acetate fraction and xanthoxyloside (1) from that fraction can justify the use of the root of N. xanthoxylon in ethnomedicine to treat malaria.

Rubia cordifolia L. Crude Aerial Part Extracts Show a High Potential as Antimalarials against Chloroquine Resistant Plasmodium falciparum Strains in vitro

Pharmacognosy Research,2023,15,2,288-296.DOI:10.5530/pres.15.2.031Published:February 2023Type:Original Article Authors:Magara Jeremiah, Lucy Kamau, Grace Nyambati, and Hastings Ozwara Author(s) affiliations:Magara Jeremiah1, Lucy Kamau1, 2,*, Grace Nyambati3, Hastings Ozwara4 1Department of Zoological Sciences, Kenyatta University, Nairobi, KENYA. 2Department of Animal Sciences, Kenyatta University, Nairobi, KENYA. 3Department of Biomedical Sciences and Technology, The Technical University of Kenya, Nairobi, KENYA. 4Department of Tropical and Infectious Diseases, Institute of Primate Research, Nairobi, KENYA. Abstract:Introduction: Plasmodium falciparum human malaria parasite is resistant to most available medicines in Africa, necessitating research for new drugs. Rubia cordifolia L. is used in traditional malaria treatment in Kenya despite no supporting scientific data. Objectives: To evaluate anti-plasmodial efficacy of extracts from the aerial part of Rubia cordifolia against chloroquine sensitive (3D7) and resistant (W2) Plasmodium falciparum strains. Methods: Hexane, methanol and water were separately used in crude extractions from open shade dried aerial plant parts. Phytochemical composition was determined qualitatively. Anti-plasmodial efficacy of serial dilutions (range; 0.4 to 50 μg/ml) of each extract were evaluated in vitro and compared using ANOVA and Tukey’s HSD test, at p<0.05). Results: All the extracts significantly inhibited parasites growth, in a dose dependent manner. At 50 μg/ml, inhibition was (84.07%, 77.94% and 66.08%) for hexane, methanol and water extracts respectively against W2 and (80.06%, 78.36% and 60.92%) against 3D7 strain. Hexane extract showed IC50 0.551 μg/ml and 2.747 micrograms/ml against W2 and 3D7 respectively. Methanol extract, IC50 1.231 and 3.528 μ g/ml respectively, aqueous extract showed moderate activity, IC50 5.348 μg/ml and 17.341 μg/ml against the strains respectively. Chloroquine resistant (W2 strain) was more responsive to the extracts than 3D7 strain. Conclusion: Anti-plasmodial activities were in the order, Hexane>methanol>aqueous and were attributed to the phytochemicals present in the extracts. This presents evidence of R. cordifolia as anti-malarial drugs’ source. Further work is required to identify, purify, and characterize active molecules for development of anti-malaria drugs. Keywords:Antimalarial activity, Crude extracts, in vitro, Plasmodium falciparum, Rubia cordifolia.View:PDF (236.96 KB)

Chitosan-supported FeCl3 catalyzed multicomponent synthesis of tetrahydroisoquinoline-indole hybrids with promising activity against chloroquine resistant Plasmodium falciparum

An operationally simple three-component coupling of tetrahydroisoquinoline (THIQ), aldehydes and indoles or indole-3-carboxylic acids has been achieved using chitosan-ionic liquid supported FeCl3 (chit-IL@FeCl3) as a recyclable heterogeneous catalyst. The developed waste-free approach provided rapid access to biologically important THIQ-indole hybrids without the use of any additive or ligand. The synthesized THIQ-indole hybrids were evaluated as antiplasmodial agents against chloroquine-sensitive (Pf3D7) and chloroquine-resistant (PfINDO) strains of Plasmodium falciparum. Compounds 4b (most potent against Pf3D7) and 4g (most potent against PfINDO) showed IC50 values of 1.32 and 0.26 µg/mL respectively. Also, 4g showed strong cytocidal action against both rings and trophozoite stages. Furthermore, cytotoxic study against human liver HUH 7 cells revealed that the most potent compound 4g with an excellent resistance index of 0.07 is also relatively non-toxic. The results of this study suggest that THIQ-indole hybrids hold an enormous potential for developing new antimalarial agents with novel mechanism of action.

Pharmacological Study of Azadirachta indica (Neem) for their possible Antimalarial Activity with Emphasis on Resistance and Resistant Reversal

Malaria is one of the deadliest and oldest disease known to mankind for more than 2000 years that causes the death of 0.4 million individuals in 2009. In the era of resistance, multi-drug resistance, finding a new efficacious &amp; potent molecule is always a challenge for Pharmacological science. Researcher across the globe see resistance threat in every molecule. Every drug, molecule whether new or old have resistance possibility. Therefore, researcher in this study tried to understand the behavior of chloroquine-resistant plasmodium yoelii nigeriensis (PYn) which is most experimented &amp; reported animal malaria model equivalent to plasmodium vivax in human with chloroquine &amp; the possibility of resistance reversal for some herbal extracts. 2-20 times chloroquine doses (10-100 mg/ kg) are not able to produce sufficient efficacy in chloroquine resistant PYn. Where 5 mg/ kg dose of chloroquine is effective dose against the chloroquine sensitive dose. Same while, most of the plant extracts are also not able to produce minimal therapeutic response on Chloroquine resistant plasmodium when given alone. However, plant extracts Azadirachta indica (AI) at 300 mg/ kg &amp; 1000 mg/ kg shows a better effect when given with chloroquine 20 mg/ kg then alone. Out of all plant extracts hydroalcoholic extracts of dried leaves &amp; ethanolic extract of dried bark of AI. Current approach of multi-drug dosage supports also supported here in the study with a thought of using antimalarial plant extracts during regular malaria treatment. Genesis of idea of referring standardized plant extract(s) in combination as oral dosage with prophylactic (travelers) malaria &amp; malaria treatment or side-food for malaria will also possible. Positive results may pave a path for inclusion of herbal extracts or herbs as side treatment or drug resistance-breaker food for malaria.

A Study of the Antimalarial Activity of Combined Plant Extracts Traditionally Used in Kenya

Introduction: Due to resistance and cost of current antimalarial drugs in use, there is need to continue searching for effective and affordable treatment for this disease. Traditional medicinal plants have been focused on as source of such drugs.&#x0D; Methodology: For this study, combined crude extracts from six plants used in Kenya were tested in vitro against chloroquine resistant Plasmodium falciparum W2 strain using the [3H] hypoxanthine uptake assay and in vivo using Plasmodium berghei on mice. Cytotoxicity tests were done using the MTT based colorimetric assay on Vero 199 and selectivity index used to assess safety of the extracts with the best activity.&#x0D; Results: In vitro results with combinations involving Zanthoxylum chalybeum with four of the extracts indicated activity below IC50 10µg/ml. A combination of S. pinnata and Toddalia asiatica extracts exhibited the best activity in vivo having a parasite growth suppression of 81.3% at a dose of 500mg/kg. S. pinnata and T.asiatica combination had CC50 values of 102.93±5.96µg/ml and &gt;1000µg/ml with selectivity indices of 9.52 and 15.24 respectively, indicating good therapeutic potential due to their safety margins.&#x0D; Conclusion: The results obtained from both in vitro and in vivo tests support the use of the plants selected in traditional treatment of malaria. A combination of methanol fruit extract of T. asiatica and methanol whole plant extract of S. pinnata showed promising parasite growth suppression against P. berghei that was comparable with Artemether and was synergistic on in vitro testing against chloroquine- resistant W2 strain of P. falciparum.

Histopathological Changes in Kidneys of Developing Chick Embryo on Exposure to Artesunate

Introduction: Chick embryo is one of the most commonly used animals to study the adverse effects of various drugs for research purpose. In India, Malaria imposes incredible socio-economic burden on humankind. India reports approximately two million cases of malaria yearly, with large number of deaths. Surveys have demonstrated that the rates of treatment failure are higher than 50% due to Chloroquine resistance and poor efficacy of Sulphadoxine Pyrimethamine. Artesunate is a concentrate of Artemisia plant found in China, also called as Qinghaosu. It is a subordinate of a group of drugs artemisinin that have the most rapid action of all current drugs against Chloroquine resistant Plasmodium vivax and Plasmodium falciparum malaria. Aim: To understand the adverse effects of Artesunate on kidney of developing chick embryo. Materials and Methods: The present study was an experimental study which comprised of steps like selection and sampling of eggs in groups (control and experimental), selection and preparation of drug (dose titration), drug administration, incubation of eggs, manual hatching to obtain chick embryo, isolation of kidney, sectioning of kidney and staining for slide preparation, microscopical analysis of the slides. In this study, the fertilised eggs used were of White Leghorn chicken and were procured from King and King poultry farm Hapur, Uttar Pradesh, India. Hundred fertilised chicken eggs were divided into five experimental groups denoted by A, B, C, D, and E and five control groups denoted by a, b, c, d and e one for each experimental group respectively. Each experimental and control group had 10 eggs. Experimental groups A, B, C, D and E were exposed to artesunate with dose of 0.0004 mg, 0.0005 mg, 0.0006 mg, 0.0007 mg and 0.0008 mg respectively and control group a, b, c, d and e were treated with same concentration of normal saline as artesunate. The eggs were broken by scalpel on 18th day of incubation and chick embryos were obtained. The kidneys were removed sectioned, stained and studied using light and compound microscope. Results: Histopathological changes like tubular degeneration, vacuolation in the cytoplasm of epithelium lining of Proximal Convoluted Tubules (PCT) and Distal Convoluted Tubules (DCT), congestion in Glomeruli, haemorrhage in urinary space and mild lymphocytic infiltration were observed. Conclusion: Exposure to artesunate increases the risk of nephrotoxicity with increase of embryonic age.

Chloroquine inhibits pro-inflammatory effects of heme on macrophages and invivo

BackgroundChloroquine has been used successfully to treat Malaria, including by chloroquine-resistant Plasmodium sp., indicating that it has effects on disease itself. Since heme has inflammatory effects and contributes to the pathogenesis of hemolytic diseases, we hypothesize that the anti-inflammatory effect of chloroquine is partially due to its inhibitory effect on heme-induced macrophage activation and on inflammatory tissue damage. MethodsBone marrow derived macrophages (BMDMs) were incubated with chloroquine before stimulation with heme, in different conditions, to evaluate cytokines secretion, ROS production, mitogen activated protein kinases (MAPK) or spleen tyrosine kinase (Syk) activation, alone or combined with LPS. The effects of chloroquine upon heme inflammation were also evaluated in vivo, through simultaneous i.p. injection of LPS and heme, intratracheal instillation of Poly-IC followed by heme injection, and in a rhabdomyolysis model. ResultsChloroquine inhibited TNF secretion, mitochondrial ROS production, MAPK, and Syk activation induced by heme. Inhibition of TNF production could be mimicked by zinc ionophore quercetin, but not by primaquine, a chloroquine analog with low affinity for heme. IL-6 and IL-1β secretions induced by heme in the presence of PRRs agonists were inhibited by chloroquine, but not by calcium chelator BAPTA or inhibitor of endosomal acidification concamycin B. Chloroquine also protected mice from heme inflammatory effects in vivo, inhibiting lethal synergism with PRR agonists, lung pathology caused by heme injection after intratracheal instillation of Poly-IC, and delaying death after rhabdomyolisis. ConclusionOur data indicate that chloroquine might be used as a supportive therapy to control heme-induced deleterious inflammation in different hemolytic diseases.

Discoveries and Syntheses of Highly Potent Antimalarial Troponoids.

Novel derivatives of puberulic acid were synthesized and their antimalarial properties were evaluated in vitro against the Plasmodium falciparum K1 parasite strain, cytotoxicity against a human diploid embryonic cell line MRC-5, and in vivo efficacy using a Plasmodium berghei-infected mouse model. From previous information that three hydroxy groups on the tropone framework were essential for antimalarial activity, we converted the carboxylic acid moiety into the corresponding esters, amides, and ketones. These derivatives showed antimalarial activity against chloroquine-resistant Plasmodium in vitro equivalent to puberulic acid. We identified that the pentane-3-yl ester, cyclohexyl ester, iso-butyl ketone, cyclohexyl methyl ketone all show an especially potent antiparasitic effect in vivo at an oral dose of 15 mg/kg without any apparent toxicity. These esters were more effective than the existing commonly used antimalarial drug, artesunate.

Quinolinotriazole antiplasmodials via click chemistry: synthesis and in vitro studies of 7-Chloroquinoline-based compounds

Malaria is nowadays one of the most serious health concerns in a global scale and, although there is an evident increase in research studies in this area, pointed by the vast number of hits and leads, it still appears as a recurrent topic every year due to the drug resistance shown by the parasite exposing the urgent need to develop new antimalarial medications. In this work, 38 molecules were synthesized via copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) or “click” chemistry, following different routes to produce 2 different organic azides, obtained from a 4,7 dicholoquinoline, reacted with 19 different commercially available terminal alkynes. All those new compounds were evaluated for their in vitro activity against the chloroquine resistant malaria parasite Plasmodium falciparum (W2). The cytotoxicity evaluation was accomplished using Hep G2 cells and SI index was calculated for every molecule. Some of the quinoline derivatives have shown high antimalarial activity, with IC50 values in the range of 1.72-8.66 µM, low cytotoxicity, with CC50>1000 µM and selectivity index (SI) in the range of 20-100, with some compounds showing SI>800. Therefore, the quinolinotriazole hybrids could be considered a very important step on the development of new antimalarial drugs.

An unlabelled probe-based real time PCR and modified semi-nested PCR as molecular tools for analysis of chloroquine resistant Plasmodium vivax isolates from Afghanistan

BackgroundPlasmodium vivax resistance to chloroquine (CQ) has been reported from many endemic regions in the world. Plasmodium vivax is responsible for 95% of malaria cases in Afghanistan and CQ is the first-line treatment given for vivax malaria. The pvmdr-1 and pvcrt-o (K10 insertion) genes are possible markers for CQ-resistance in P. vivax isolates. There have been no studies done on the presence or absence of molecular markers for CQ-resistance P. vivax in Afghanistan. The present work aimed to evaluate the frequency of mutations in the pvmdr-1 and K10 insertion in the pvcrt-o genes of P. vivax.MethodsPlasmodium vivax isolates were collected from Laghman, Baghlan and Khost provinces. For investigation of polymorphisms of desired regions in pvmdr-1 and pvcrt-o genes, sequencing was applied on the PCR products. A new asymmetric qPCR and melting analysis assay based on unlabelled probe developed for scanning of K10 insertion in pvcrt-o gene.ResultsThe analysis of sequencing data of the pvmdr-1 gene showed wild type Y976 and K997 and mutant M958 and L1076 in 33 isolates from three provinces. Of the 36 samples evaluated for K10 insertion in pvcrt-o, 2/18(11%), 0/10(0%) and 0/8(0%) isolates from Laghman, Baghlan and Khost province, respectively, possessed K10 insertion, confirmed by either sequencing and unlabelled probes.ConclusionTwo samples with K10 insertion and 33 samples with pvmdr1 polymorphism, indicating on the possibility of CQ resistance in P. vivax populations in Afghanistan. Furthermore, unlabelled probes are simple and inexpensive alternative tools for screening of P. vivax mutations.

Nonclinical safety, tolerance and pharmacodynamics evaluation for meplazumab treating chloroquine-resistant Plasmodium falciparum

Meplazumab is an anti-CD147 humanized IgG2 antibody. The purpose of this study was to characterize the nonclinical safety, tolerance and efficacy evaluation of meplazumab treating chloroquine resistant Plasmodium falciparum. Meplazumab was well tolerated in repeat-dose toxicology studies in cynomolgus monkeys. No observed adverse effect level was 12 mg/kg. No difference between genders in the primary toxicokinetic parameters after repeat intravenous injection of meplazumab. No increased levels of drug exposure and drug accumulation were observed in different gender and dose groups. Meplazumab had a low cross-reactivity rate in various tissues and did not cause hemolysis or aggregation of red blood cells. The biodistribution and excretion results indicated that meplazumab was mainly distributed in the plasma, whole blood, and hemocytes, and excreted in the urine. Moreover, meplazumab effectively inhibited the parasites from invading erythrocytes in humanized mice in a time-dependent manner and the efficacy is superior to that of chloroquine. All these studies suggested that meplazumab is safe and well tolerated in cynomolgus monkeys, and effectively inhibits P. falciparum from invading into human red blood cells. These nonclinical data facilitated the initiation of an ongoing clinical trial of meplazumab for antimalarial therapy.

In silico, in vitro and in vivo evaluation of natural Bignoniaceous naphthoquinones in comparison with atovaquone targeting the selection of potential antimalarial candidates

The natural naphthoquinones lapachol, α- and β-lapachone are found in Bignoniaceous Brazilian plant species of the Tabebuia genus (synonym Handroanthus) and are recognized for diverse bioactivities, including as antimalarial. The aim of the present work was to perform in silico, in vitro and in vivo studies to evaluating the antimalarial potential of these three naphthoquinones in comparison with atovaquone, a synthetic antimalarial. The ADMET properties of these compounds were predicted in silico by the preADMET program. The in vitro toxicity assays were experimentally determined in immortalized and tumoral cells from different organs. In vivo acute oral toxicity was also evaluated for lapachol. Several favorable pharmacokinetics data were predicted although, as expected, high cytotoxicity was experimentally determined for β-lapachone. Lapachol was not cytotoxic or showed low cytotoxicity to all of the cells assayed (HepG2, A549, Neuro 2A, LLC-PK1, MRC-5), it was nontoxic in the acute oral test and disclosed the best parasite selectivity index in the in vitro assays against chloroquine resistant Plasmodium falciparum W2 strain. On the other hand, α- and β-lapachone were more potent than lapachol in the antiplasmodial assays but with low parasite selectivity due to their cytotoxicity. The diversity of data here reported disclosed lapachol as a promising candidate to antimalarial drug development.

Global assessment of genetic paradigms of Pvmdr1 mutations in chloroquine-resistant Plasmodium vivax isolates.

Chloroquine (CQ) is generally prescribed as the front-line antimalarial drug of choice to treat Plasmodium vivax infections; however, some clinical CQ-resistant P. vivax isolates have been indigenously reported around the world during the last decade. In this study, P. vivax isolates (n=52) were obtained from autochthonous samples in southeast Iran during 2015-2017. The genomic DNA of samples was extracted, amplified (nested PCR) and sequenced by targeting the multidrug-resistance 1 gene. To verify the global genetic diversity of CQ-resistant P. vivax strains, the sequences of Pvmdr1 originating from Asia and the Americas were retrieved. A total of 46 haplotypes were grouped into three distinct geographical haplogroups. The haplotype diversity and occurrence rates of Pvmdr1 976F/1076L mutations indicate that the efficacy of CQ is being compromised in Mexico, China, Nicaragua, Thailand, Brazil (2016), Ethiopia, Mauritania (2012) and southwest India in the near future. The cladistic phylogenetic tree showed that Pvmdr1 sequences isolated from the southeast Asian clade has a partial sister relationship with the American clade. The current findings will serve as a basis to develop appropriate malaria control strategies and public health policies in symptomatic imported malaria cases or plausible CQ-resistant P. vivax strains.

Antiplasmodial profile of selected compounds from Malaria Box: in vitro evaluation, speed of action and drug combination studies

BackgroundArtemisinin-based combination therapy (ACT) is used as the first-line treatment of uncomplicated malaria caused by the Plasmodium falciparum parasite and chloroquine-resistant Plasmodium vivax parasites. Evidence of resistance to ACT has been reported in Cambodia, and without new and effective anti-malarial agents, malaria burden and mortality will rise.MethodsThe used MolPrint 2D fingerprints and the Tanimoto similarity index were used to perform a structural similarity search within the Malaria Box collection to select diverse molecular scaffolds that are different from artesunate. Next, the inhibitory potency against the P. falciparum 3D7 strain (SYBR Green I inhibition assay) and the cytotoxicity against HepG2 cells (MTT and neutral red assays) were evaluated. Then, the speed of action, the combination profile of selected inhibitors with artesunate, and the P. berghei in vivo activity of the best compounds were assessed.ResultsA set of 11 structurally diverse compounds from the Malaria Box with a similarity threshold of less than 0.05 was selected and compared with artesunate. The in vitro inhibitory activity of each compound confirmed the reported potencies (IC50 values ranging from 0.005 to 1 µM). The cytotoxicity of each selected compound was evaluated and used to calculate the selectivity index (SI values ranging from 15.1 to 6100). Next, both the speed of action and the combination profile of each compound with artesunate was assessed. Acridine, thiazolopyrimidine, quinoxaline, benzimidazole, thiophene, benzodiazepine, isoxazole and pyrimidoindole derivatives showed fast in vitro inhibitory activity of parasite growth, whereas hydrazinobenzimidazole, indenopyridazinone and naphthalenone derivatives were slow-acting in vitro inhibitors. Combinatory profile evaluation indicated that thiazolopyrimidinone and benzodiazepine derivatives have an additive profile, suggesting that the combination of these inhibitors with artesunate is favourable for in vitro inhibitory activity. The remaining compounds showed an antagonistic combinatory profile with artesunate. The collected data indicated that the indenopyridazinone derivative, a bc1 complex inhibitor, had a similar association profile in combination with proguanil when compared to atovaquone combined with proguanil, thereby corroborating the correlation between the molecular target and the combination profile. Lastly, the in vivo activity of the thiazolopyrimidinone and benzodiazepine derivatives were assessed. Both compounds showed oral efficacy at 50 mg/kg in a mouse model of Plasmodium berghei malaria (64% and 40% reduction in parasitaemia on day 5 post-infection, respectively).ConclusionsThe findings in this paper shed light on the relationship among the speed of action, molecular target and combinatory profile and identified new hits with in vivo activity as candidates for anti-malarial combination therapy.

Antiplasmodial Bis-Indole Alkaloids from the Bark of Flindersia pimenteliana.

Three new (1: -3: ) and 2 known (4: -5: ) bis-indole alkaloids were identified from the bark of Flindersia pimenteliana (Rutaceae). The structures of 1: -3: were elucidated on the basis of their (+)-HRESESIMS and 2D NMR spectroscopic data. Antiplasmodial activity for 1: -3: against chloroquine sensitive (3D7) and chloroquine-resistant (Dd2) Plasmodium falciparum is also reported, with IC50 values ranging from 0.96 to 2.41 µg/mL. These results expand our knowledge of the structure-activity relationships of potently antiplasmodial isoborreverine-type alkaloids, the bioactivity of which have recently attracted significant attention in the literature.

A CASE OF TROPICAL ILLNESS MANAGED IN THE MEDICAL ICU WITH AN INVESTIGATIONAL NEW DRUG

SESSION TITLE: Case Report Semifinalists 3 SESSION TYPE: Fellow Case Report Posters PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: Rates of international travel are increasing along with increasing exposure to tropical diseases. It is of importance to maintain knowledge of common tropical diseases and treatment options. CASE PRESENTATION: A 30-year-old male, who returned a week prior from admission, from a vocational trip to Nigeria. Patient presented with symptoms of headache, fever, nausea, vomiting, abdominal pain and diarrhea. Patient was septic but otherwise hemodynamically stable, with presenting labs demonstrating profound thrombocytopenia with low haptoglobin (table 1) and presence of malaria on Wright-Giemsa stain. Blood smear demonstrated 17% Plasmodium Falciparum paracitemia. The Center of Disease Control(CDC) was contacted. Patient was started on treatment with intravenous(IV) quinidine and doxycycline and admitted to the Medical Intensive Care Unit(MICU) for further monitoring. Due to lack of available IV quinidine to complete therapy the decision was made to transition to IV artesunate and continued on doxycycline. Hospital course remained uncomplicated with quick resolution of parasitic loads (<1%). DISCUSSION: Malaria with Plasmodium Falciparum occurring in certain geographical areas, including Nigeria, are categorized by the CDC as a chloroquine resistant. Four applicable pharmacological therapies are available in such cases: atovaquone-proguanil, artemether-lumefantrine, quinine in combination with doxycycline, tetracycline or clindamycin and mefloquine. Quinine is the only FDA approved IV medication for treatment of severe malaria. The CDC defines severe malaria by the presence of one of more specifically defined clinical signs and symptoms and/or parasitemia of >5%. Our patient was stratified into a category of severe malaria by presence of a paracitemia of 17%. Per CDC recommendations severe malaria should be treated with IV antimalarial medication. World Health Organization recommends artesunate over quinine therapy for severe malaria. The FDA has approved artesunate as an investigational option in certain individuals who qualify. CONCLUSIONS: Artesunate is an effective alternative treatment option for individuals with severe malaria. We demonstrate a case of successful treatment of severe chloroquine resistant plasmodium falciparum malaria with artesunate. Reference #1: Centers for Disease Control and Prevention. (2018). Treatment of Malaria: Guidelines For Clinicians (United States) Reference #2: Dilip R. Karnad, MD, Guy A. Richards, MD PhD, Gisele Sampaio Silva, MD, Pravin Amin, MD. Tropical diseases in the ICU: A syndromic approach to diagnosis and treatment. Journal of Critical Care 46(2018)119-126 DISCLOSURES: No relevant relationships by Shozab Ahmed, source=Web Response No relevant relationships by Monika Kakol, source=Web Response