Chloroquine-resistant Plasmodium Research Articles

Ruthenium(II) arene complexes with chelating chloroquine analogue ligands: synthesis, characterization and in vitro antimalarial activity.

Three new ruthenium complexes with bidentate chloroquine analogue ligands, [Ru(η(6)-cym)(L(1))Cl]Cl (1, cym = p-cymene, L(1) = N-(2-((pyridin-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine), [Ru(η(6)-cym)(L(2))Cl]Cl (2, L(2) = N-(2-((1-methyl-1H-imidazol-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine) and [Ru(η(6)-cym)(L(3))Cl] (3, L(3) = N-(2-((2-hydroxyphenyl)methylimino)ethyl)-7-chloroquinolin-4-amine) have been synthesized and characterized. In addition, the X-ray crystal structure of 2 is reported. The antimalarial activity of complexes 1-3 and ligands L(1), L(2) and L(3), as well as the compound N-(2-(bis((pyridin-2-yl)methyl)amino)ethyl)-7-chloroquinolin-4-amine (L(4)), against chloroquine sensitive and chloroquine resistant Plasmodium falciparum malaria strains was evaluated. While 1 and 2 are less active than the corresponding ligands, 3 exhibits high antimalarial activity. The chloroquine analogue L(2) also shows good activity against both the chloroquine sensitive and the chloroquine resistant strains. Heme aggregation inhibition activity (HAIA) at an aqueous buffer/n-octanol interface (HAIR(50)) and lipophilicity (D, as measured by water/n-octanol distribution coefficients) have been measured for all ligands and metal complexes. A direct correlation between the D and HAIR(50) properties cannot be made because of the relative structural diversity of the complexes, but it may be noted that these properties are enhanced upon complexation of the inactive ligand L(3) to ruthenium, to give a metal complex (3) with promising antimalarial activity.

Triterpenes from Minquartia guianensis (Olacaceae) and in vitro antimalarial activity

Minquartia guianensis, popularly known as acariquara, was phytochemically investigated. The following triterpenes were isolated from the dichloromethane extract of leaves: lupen-3-one (1), taraxer-3-one (2) and oleanolic acid (3). The dichloromethane extract of branches yielded the triterpene 3β-methoxy-lup-20(29)-ene (4). The chemical structures were characterized by NMR data. Plant extracts, substance 3, squalene (5) and taraxerol (6), (5 and 6 previously isolated), were evaluated by in vitro assay against chloroquine resistant Plasmodium falciparum. The dichloromethane extract of leaves and the three triterpenes assayed have shown partial activity. Thus, these results demonstrated that new potential antimalarial natural products can be found even in partially active extracts.

Prevalence of severe chloroquine resistance associates the point mutation in pfcrt and pfmdrI gene in eastern India

Objective To evaluate the molecular mechanism of chloroquine resistant Plasmodium falciparum malaria in West Bengal, eastern part, India. Methods Parasitic bloods were collected from patients in Kolkata and Purulia, in vitro drug susceptibility test were performed in those 179 isolates. Now parasitic DNA was isolated by phenol chloroform extraction method and then polymerase chain reaction and restriction fragment length polymorphism analysis of different codons of pfcrt gene (76) and the pfmdrI gene (86, 1246) were assessed. Results The response of 179 patients to chloroquine was determined. The prevalence of both pfcrt K76T (68.72%) and pfmdrI N86Y (43.1%) mutation was found here. But most importantly severe in vitro chloroquine resistance has been found (53.07%) here, with either double 76T + 86Y mutation or triple 76T + 86Y + 1246Y mutation. Conclusions Our present findings implicate that due to enormous drug (chloroquine) pressure, double mutation with pfcrt 76T + pfmdrI 86Y and triple mutation with pfcrt 76T + pfmdrI 86Y + pfmdrI 1246Y was highly correlated ( P = 0.001) with in vitro chloroquine resistance for the first time in eastern India.

Synthesis and antimalarial evaluation of novel isocryptolepine derivatives

A series of mono- and di-substituted analogues of isocryptolepine have been synthesized and evaluated for in vitro antimalarial activity against chloroquine sensitive (3D7) and resistant (W2mef) Plasmodium falciparum and for cytotoxicity (3T3 cells). Di-halogenated compounds were the most potent derivatives and 8-bromo-2-chloroisocryptolepine displayed the highest selectivity index (106; the ratio of cytotoxicity (IC50=9005nM) to antimalarial activity (IC50=85nM)). Our evaluation of novel isocryptolepine compounds has demonstrated that di-halogenated derivatives are promising antimalarial lead compounds.

English

Methanolic leaf and root extracts of Sphenocentrum jollyanum Pierre were tested in vivo for anti-malarial activity in Swiss albino mice inoculated with chloroquine resistant Plasmodium berghei NK 67 strain. The two extracts exhibited a significant (p>0.05) dose dependant anti-plasmodial activities in isolation and when combined in the 4-days curative standard test with a high mean of survival time. Although, the standard drug, Arthemether - lumefartrin, showed the highest antimalaria potency (81.4%), those of the leaf (74.4%) and root extracts (54.1%) in isolation and combination (63.4%) compared favorably. The leaf extract demonstrated higher antimalarial potency than the root or combination.  The two extracts also produced a significant (p>0.05) positive effect on the weight and hematology values in the treated animals. Phytochemical screening of the plant (leaf and the root extracts) reveals the presences of flavonoids, steroids, terpenoids, tannins and alkaloids. The anti-plasmodia activity of these plant extract might be attributed to these phytochemicals compounds. The results showed that the leaf and root of S. jollyanum possesses an anti-malarial activity which was effective against chloroquine resistance strain. This work has validated the traditional uses of S. jollyanum root extract in the treatment of malaria and also reported for the first time the anti-malarial property of the S. jollyanun leaf extract.   Key words: Sphenocentrum jollyanum, Plasmodium berghei, Arthemther lumefartrin, hematological parameter, anti-plasmodium.

Antimalarial efficacy of piperaquine-based antimalarial combination therapies: facts and uncertainties

Piperaquine is a bisquinoline antimalarial drug extensively used as monotherapy in China in the 1980s and subsequently included as one of the components of the artemisinin-based combination therapies (ACTs) in the 1990s. Among them, dihydroartemisinin-piperaquine (DHA-PQP) represents a new and extremely promising fixed combination. Several clinical trials have repeatedly shown that DHA-PQP is a safe and highly efficacious therapy against uncomplicated Plasmodium falciparum and the asexual stages of Plasmodium vivax malaria. Studies conducted with this drug have reported cure rates consistently above 95%, with the only exception being a study carried out in Papua New Guinea which reported a high rate of treatment failures. Although it has been hypothesized that such treatment failures could be related to cross-resistance mechanisms between piperaquine and other quinolines or to a reduced susceptibility of parasites to artemisinin derivatives, a critical review of the studies published so far seems to exclude both of these possibilities. Overall, there is now sufficient evidence on the safety and efficacy of the DHA-PQP therapy. Accordingly, the use of this ACT for the treatment of P.falciparum malaria has been recently approved in the EU via a centralized procedure by the European Medicines Agency. Moreover, it is now recommended globally by the World Health Organization as an option for the first-line treatment of uncomplicated malaria.

Interaction between ciprofloxacin and chloroquine in mice infected with chloroquine resistant Plasmodium berghei

The increasing spread of chloroquine resistant malaria has intensified the search for new antimalarial treatment, especially drugs that can be used in combination. Ciprofloxacin (CFX) a fluoroquinolone commonly used to treat bacterial infections has been shown to possess significant antimalarial activity both in vitro and in vivo. Thus efforts in this study were devoted to evaluating the antimalarial activity of combination of chloroquine (CQ) with varying doses (10, 20, 40 80, 160 mg/kg body weight) of CFX in groups of 35 mice inoculated intraperitoneally with 10(7) chloroquine resistant strain Plasmodium berghei ANKA. Parasitological activity and survival of the animals were assessed over 21 days. Parasitemia in non-treated control mice peaked at 78% on day 9 and none survived by day 10. However, the combination of CQ with 160 mg/kg body weight of CFX resulted in a reduction in parasitemia between days 9 and 14 and this was significantly lower than that obtained with CQ alone or CQ combined with the lower doses of CFX (p < 0.05). In addition, the combination of CQ with 160 mg/kg CFX significantly reduced mortality in the infected animals (p = 0.0002) compared with the other treatment groups. The results from this study support the potential usefulness of CFX in combination with antimalarial drugs for the treatment of chloroquine resistant human malaria.

The antiplasmodial effect of the extracts and formulated capsules of Phyllanthus amarus on Plasmodium yoelii infection in mice

Objective To investigate the antiplasmodial activity of the extracts of Phyllanthus amarus (P. amarus) on Plasmodium yoelii (P. yoelii) (a resistant malaria parasite strain used in animal studies) infection in mice. Methods The aqueous and ethanol extracts of the whole plant of Phyllanthus amarus was administered to Swiss albino mice at doses of 200 mg/kg/day, 400 mg/kg/day, 800 mg/kg/day and 1600 mg/kg/day and the prophylactic and chemotherapeutic effect of the extracts against P. yoelii infection in mice was investigated and compared with those of standard antimalaria drugs used in the treatment of malaria parasite infection. Acute toxicity test was carried out in mice to determine the safety of the plant extract when administered orally. Results The results showed that the extracts demonstrated a dose—dependent prophylactic and chemotherapeutic activity with the aqueous extracts showing slightly higher effect than the ethanol extract. The antiplasmodial effects of the extracts were comparable to the standard prophylactic and chemotherapeutic drugs used in chloroquine resistant Plasmodium infection although the activity depended on the dose of the extract administered. The extracts showed prophylactic effect by significantly delaying the onset of infection with the suppression of 79% at a dose of 1600 mg/kg/day. Conclusions The results obtained indicate that the extracts of the whole plant of P. amarus possess repository and chemotherapeutic effects against resistant strains of P. yoelii in Swiss albino mice. The findings justify the use of the extract of P. amarus in traditional medicine practice, for the treatment of malaria infections.

FALCIPARUM MALARIA

Introduction: Quinine and quinidines remain the drugs of choice for chloroquine resistant Plasmodium falciparum malaria. In 1972, Chinese scientists discovered the antimalarial properties of a group of compounds from the qinghao plant (Artemisia annua) which have activity against all malaria causing parasites including multi-drug resistant strains of Plasmodium falciparum. Objective: To compare response to treatment between quinine and artemether in Plasmodium falciparum malaria. Design: Quasi-experimental study. Setting: Department of Medicine Pakistan Air Force Hospital Lahore. Period: 1st Jun 2008 to 1st Dec 2009. Patients: 80 consecutive adult patients with positive MP slide for Plasmodium falciparum malaria. Methods: Patients were randomly divided into two groups for treatment either with quinine or artemether. Results: Out of total 80 patients, 40 were given quinine and 40 were given artemether. Out of 40, 16 patients responded to quinine while 24 did not respond. The responders were 34.8% in case of quinine while 70.6% patients did not respond. Out of 40 patients treated with artemether, 30 responded while 10 did not. The responders were 65.2%while non responders were 29.4%.0n calculating the P-value from the chi-square it was found that difference in terms of response to the two treatment regimens was statistically significant.(P=.0022).Conclusion: The frequency of response in case of quinine was 34.8% while it was 65.2% in case of artemether. So based upon statistically significant difference (P=.0022) it is concluded that Artemether is a satisfactory alternative to Quinine for the treatment of falciparum malaria in adults.

Traditional herbal antimalarial therapy in Kilifi district, Kenya

To identify plant species used by the traditional health practitioners (THPs) in treatment of malaria, carry out cytotoxicity and efficacy evaluation of the identified plants and to evaluate combination effects. Thirteen plants were selected through interviews with traditional healers. In vitro antiplasmodial testing was done by measuring ability of the test sample to inhibit the incorporation of radio-labelled hypoxanthine into the malaria parasite. The extracts were tested singly and then in combination using the standard fixed ratio analysis to evaluate synergism. In vivo bioassay was done in mice using Peter's 4-days suppressive test and cytotoxicity evaluated in vitro using Vero E6 cells. Of the plants tested in vitro, 25% were highly active (IC(50)<10 μg/ml), 46% moderately active (IC(50) 10-50 μg/ml), 16% had weak activity of 50-100 μg/ml while 13% were not active IC(50) >100 μg/ml. Methanolic extracts of Azadirachta indica, Premna chrysoclada and Uvaria acuminata were the most active (IC(50)<10μg/ml) against both the chloroquine (CQ) sensitive (D6) and the CQ resistant (W2) Plasmodium falciparum clones. When tested in vivo in a mouse model, Azadirachta indica, Rhus natalensis and Grewia plagiophylla depicted the highest percent parasite clearance and chemo suppression of 89%, 82% and 78%, respectively. Evaluating effect of combining some of these extracts with one another against a multi-drug resistant Plasmodium falciparum (W2) clone revealed synergism among some combinations. The highest synergy was between Uvaria acuminata and Premna chrysoclada. The interaction between Grewia plagiophylla and Combretum illairii was largely antagonistic. Impressive cytotoxicity results were obtained with most of the plants tested revealing high selectivity indices an indication of enabling achievement of therapeutic doses at safe concentrations. Uvaria acuminata was, however, toxic to the cultured cells. Mild cytotoxicity was also observed in Hoslundia opposita and Lannea schweinfurthii (CC(50) 37 and 76 μg/ml, respectively). This study identified plants with low IC(50) values, high percent chemo suppression and low cytotoxicity thus potential sources for novel antiplasmodial agents. The findings remotely justify use of combined medicinal plants in traditional medicine practices as synergy among some plant species was demonstrated.

QSAR studies of some side chain modified 7-chloro-4-aminoquinolines as antimalarial agents

The quantitative structure–activity relationship (QSAR) analyses were carried out for a series of new side chain modified 4-amino-7-chloroquinolines to find out the structural requirements of their antimalarial activities against both chloroquine sensitive (HB3) and resistant (Dd2) Plasmodium falciparum strain. The statistically significant best 2D QSAR models for Dd2, having correlation coefficient (r2)=0.9188 and cross validated squared correlation coefficient (q2)=0.8349 with external predictive ability (pred_r2)=0.7258 and for HB3, having r2=0.9024, q2=0.8089 and pred_r2=0.7463 were developed by multiple linear regression coupled with genetic algorithm (GA–MLR) and stepwise (SW–MLR) forward algorithm, respectively. The results of the present study may be useful on the designing of more potent analogues as antimalarial agents.

Analysis of the dihydrofolate reductase-thymidylate synthase gene sequences in Plasmodium vivax field isolates that failed chloroquine treatment

BackgroundTo use pyrimethamine as an alternative anti-malarial drug for chloroquine-resistant malaria parasites, it was necessary to determine the enzyme's genetic variation in dihydrofolate reductase-thymidylate syntase (DHFR-TS) among Korean strains.MethodsGenetic variation of dhfr-ts genes of Plasmodium vivax clinical isolates from patients who did not respond to drug treatment (n = 11) in Korea were analysed. The genes were amplified using the polymerase chain reaction (PCR) with genomic DNA as a template.ResultsSequence analysis showed that the open reading frame (ORF) of 1,857 nucleotides encoded a deduced protein of 618 amino acids (aa). Alignment with the DHFR-TS genes of other malaria parasites showed that a 231-residue DHFR domain and a 286-residue TS domain were seperated by a 101-aa linker region. This ORF shows 98.7% homology with the P. vivax Sal I strain (XM001615032) in the DHFR domain, 100% in the linker region and 99% in the TS domain. Comparison of the DHFR sequences from pyrimethamine-sensitive and pyrimethamine-resistant P. vivax isolates revealed that nine isolates belonged to the sensitive strain, whereas two isolates met the criteria for resistance. In these two isolates, the amino acid at position 117 is changed from serine to asparagine (S117N). Additionally, all Korean isolates showed a deletion mutant of THGGDN in short tandem repetitive sequences between 88 and 106 amino acid.ConclusionsThese results suggest that sequence variations in the DHFR-TS represent the prevalence of antifolate-resistant P. vivax in Korea. Two of 11 isolates have the Ser to Asn mutation in codon 117, which is the major determinant of pyrimethamine resistance in P. vivax. Therefore, the introduction of pyrimethamine for the treatment of chloroquine-resistant vivax malaria as alternative drug in Korea should be seriously considered.

Antiplasmodial activity of three bisbenzylisoquinoline alkaloids from the tuber of Stephania rotunda

Three bisbenzylisoquinoline alkaloids were isolated for the first time from Stephania rotunda tuber. Their structures were elucidated by spectroscopic methods and their antiplasmodial activity was investigated in vitro on chloroquine resistant Plasmodium falciparum strain W2. These alkaloids were identified as 2-norcepharanthine (1), cepharanoline (2) and fangchinoline (3). In vitro, they displayed significant antiplasmodial activity with inhibitory concentration 50 values of 0.3, 0.2 and 0.3 µM.

Anti-malarial herbal remedies of northeast India, Assam: An ethnobotanical survey

Malaria is a serious public health problem in the north-eastern region of India including Assam, in view of development of chloroquine resistant Plasmodium falciparum. There is need for alternative and affordable therapy. This study was conducted to document indigenous knowledge, usage customs and practices of medicinal plant species traditionally used by the residents of Sonitpur district of Tezpur, Assam to treat malaria and its associated symptoms. A total of 50 randomly selected sampling represented by male (38.76%) and female respondents (12.24%) were interviewed using a semi-structured questionnaire. The present ethno-botanical survey revealed 22 species of plants belonging to 17 botanical families were reported to be used exclusively in this region for the treatment of malaria. Verbenaceae (three species), Menispermaceae (two species), and Acanthaceae (two species) botanical families represented the species that are most commonly cited in this survey work and the detailed use of plants has been collected and described. The most serious threat to the existing knowledge and practice on traditional medicinal plants included cultural change, particularly the influence of modernization and lack of interests shown by the next younger generations were the main problems reported by the informants during the field survey. Hence, the proper documentation of traditional medicinal plants being used as anti-malarial agents and related indigenous knowledge held by the tribal community is an important approach to control the spread of vector-borne diseases like malaria reported in this survey work.

&lt;i&gt;In vitro&lt;/i&gt; antiplasmodial properties of &lt;i&gt;Flacourtia flavescens&lt;/i&gt; willd. (&lt;i&gt;Flacourtiaceae&lt;/i&gt;) and &lt;i&gt;Rytigynia canthioides&lt;/i&gt; (benth.) Robyns (rubiaceae)

The present study was conducted to investigate the in vitro antimalarial activity of Flacourtia flavescens Willd. (Flacourtiaceae) and Rytigynia canthioides (Benth.) Robyns (Rubiaceae). These two plants are used in Benin folk medicine to treat malaria and fever. Antimalarial activity was assayed on fresh clinical isolates of chloroquine resistant Plasmodium falciparum using the in vitro semi-microtest. The results revealed that the IC(50) varied from 1.55 to 22.36µg/ml. F. flavescens hydro methanol extract was more active than R. canthioides. The study demonstrated scientific rationale behind the traditional usage of these plants, however further bioactivity guided phytochemical analyses are necessary to identify the active principles.

ChemInform Abstract: Extraordinarily Potent Antimalarial Compounds: New, Structurally Simple, Easily Synthesized, Tricyclic 1,2,4-Trioxanes.

New, racemic, tricyclic trioxane alcohol 3 was designed and synthesized as a structurally simple analog of clinically useful, tetracyclic, antimalarial artemisinin. A series of 20 ester and ether derivatives of alcohol 3 were prepared easily, without destruction of the essential trioxane system. Chemical structure-antimalarial activity for each derivative was evaluated in vitro against chloroquine-resistant and chloroquine-sensitive Plasmodium falciparum parasites. Many of these derivatives were highly efficacious; carboxylate ester 9f, carbamate ester 10a, and sulfonate ester 12a had antimalarial potency similar to that of artemisinin, and carboxylate esters 9b and 9d, carbamate esters 10b and 10c, and phosphate esters 11a-c had antimalarial potency up to 7 times higher than that of artemisinin. Several of these most active analogs (e.g., carboxylate 9b and carbamates 10a and 10c) are stable crystalline solids, a feature of considerable practical value for any new drug candidate.

Efflux of a range of antimalarial drugs and ‘chloroquine resistance reversers’ from the digestive vacuole in malaria parasites with mutant PfCRT

Chloroquine-resistant malaria parasites (Plasmodium falciparum) show an increased leak of H(+) ions from their internal digestive vacuole in the presence of chloroquine. This phenomenon has been attributed to the transport of chloroquine, together with H(+), out of the digestive vacuole (and hence away from its site of action) via a mutant form of the parasite's chloroquine resistance transporter (PfCRT). Here, using transfectant parasite lines, we show that a range of other antimalarial drugs, as well as various 'chloroquine resistance reversers' induce an increased leak of H(+) from the digestive vacuole of parasites expressing mutant PfCRT, consistent with these compounds being substrates for mutant forms, but not the wild-type form, of PfCRT. For some compounds there were significant differences observed between parasites having the African/Asian Dd2 form of PfCRT and those with the South American 7G8 form of PfCRT, consistent with there being differences in the transport properties of the two mutant proteins. The finding that chloroquine resistance reversers are substrates for mutant PfCRT has implications for the mechanism of action of this class of compound.

Predictive factors of severe disease secondary to falciparum malaria among travelers

Objectives To identify independent risk factors of severe falciparum malaria among travelers to endemic regions. Materials and methods A retrospective study on imported malaria into metropolitan France. The World's Health Organization severity criteria were used to classify malarial episodes. Results Nine hundred and twenty-one malarial cases were studied; 81 were severe. Independent risk factors of severe malaria were aged above 40 years, high level of parasitized erythrocytes (more than 4%), parasite acquisition in the south-eastern asian region, infection with a chloroquine resistant Plasmodium falciparum ( P. falciparum) phenotype and a self administered antimalarial treatment. Conclusion This study points out two particularly interesting results: severe malaria is significantly associated with the infection by a chloroquine resistant P. falciparum phenotype and with the parasite's acquisition in the south-eastern asian region.

Imported Chloroquine‐ResistantPlasmodium vivaxin Singapore: Case Report and Literature Review

Chloroquine-resistant Plasmodium vivax (CRPV) infection is emerging as a clinically significant problem. Detailed travel history is crucial to the management of imported malarial cases. We report a 58-year-old business traveler who returned from Indonesia and experienced relapse due to CRPV. The epidemiology and diagnostic challenges of CRPV for travel medicine clinicians are reviewed.

Bioassay-guided fractionation and in vivo antiplasmodial effect of fractions of chloroform extract of Artemisia maciverae Linn

In the search for new plant-derived anti-malarial compounds, chromatographic fractions of chloroform extract of whole plants of Artemisia maciverae were tested in vivo using chloroquine resistant and chloroquine sensitive Plasmodium berghei NK 65 infected Swiss albino mice. One fraction and a sub-fraction of this were most active at 10/mg and cleared parasitemia in mice within 3 days. The different fractions and sub-fractions were tested with different reagents to determine the broad classes of compounds present. The active fraction tested positive for triterpenes and alkaloids, and the sub-fraction for only triterpenes. These tests suggest that the anti-malarial activities observed with these fractions may be due to these classes of compounds in the chloroform extract of the A. maciverae. Further chemical work is however required to characterize the active constituents.