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ABSTRACT: Bioassay-guided fractionation of the methanol extract of Momordica balsamina led to the isolation of two new cucurbitane-type triterpenoids, balsaminol F (1) and balsaminoside B (2), along with the known glycosylated cucurbitacins, cucurbita-5,24-diene-3β,23(R)-diol-7-O-β-D-glucopyranoside (3) and kuguaglycoside A (4). Compound 1 was acylated yielding two new triesters, triacetylbalsaminol F (5) and tribenzoylbalsaminol F (6). The structures were elucidated based on spectroscopic methods including 2D-NMR experiments (COSY, HMQC, HMBC and NOESY). Compounds 1-6, were evaluated for their antimalarial activity against the erythrocytic stages of the Plasmodium falciparum chloroquine-sensitive strain 3D7 and the chloroquine-resistant clone Dd2. Assessment of compounds (1-3 and 5, 6) activity against the liver stage of Plasmodium berghei was also performed, measuring the luminescence intensity in Huh-7 cells infected with a firefly luciferase-expressing P. berghei line, PbGFP-Luc(con). Active compounds were shown to inhibit the parasite's intracellular development rather than its ability to invade hepatic cells. Toxicity of compounds (1-3 and 5, 6) was assessed on the same cell line and on mouse primary hepatocytes through the fluorescence measurement of cell confluency. Furthermore, toxicity of compounds 1-6 towards human cells was also investigated in the MCF-7 breast cancer cell line, showing that they were not toxic or exhibited weak toxicity. In blood stages of P. falciparum, compounds 1-5 displayed antimalarial activity, revealing triacetylbalsaminol F (5) the highest antiplasmodial effects (IC(50) values: 0.4μM, 3D7; 0.2μM, Dd2). The highest antiplasmodial activity against the liver stages of P.berghei was also displayed by compound 5, with high inhibitory activity and no toxicity.
Bioorganic & medicinal chemistry 10/2011; 19(24):7474-81. · 2.82 Impact Factor
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ABSTRACT: The isolation of bioactive compounds from medicinal plants, based on traditional use or ethnomedical data, is a highly promising potential approach for identifying new and effective antimalarial drug candidates. The purpose of this review was to create a compilation of the phytochemical studies on medicinal plants used to treat malaria in traditional medicine from the Community of Portuguese-Speaking Countries (CPSC): Angola, Brazil, Cape Verde, Guinea-Bissau, Mozambique and São Tomé and Príncipe. In addition, this review aimed to show that there are several medicinal plants popularly used in these countries for which few scientific studies are available. The primary approach compared the antimalarial activity of native species used in each country with its extracts, fractions and isolated substances. In this context, data shown here could be a tool to help researchers from these regions establish a scientific and technical network on the subject for the CPSC where malaria is a public health problem.
Memórias do Instituto Oswaldo Cruz 08/2011; 106 Suppl 1:142-58. · 2.15 Impact Factor
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ABSTRACT: Abstract Background Malaria is the major cause of morbidity and mortality in Angola. The most vulnerable groups to Plasmodium falciparum infection are pregnant women and children under five years of age. The use of an intermittent preventive treatment (IPT) with sulphadoxine/pyrimethamine (SP) in pregnant women was introduced in Angola in 2006 by the National Malaria Control Programme, and currently this strategy has been considered to be used for children malaria control. Considering the previous wide use of SP combination in Angola, together to the reported cases of SP treatment failure it is crucial the evaluation of the prevalence of five mutations in pfdhfr and pfdhps genes associated to P. falciparum resistance to SP before the introduction of S/P IPT in children. Methods The study was conducted in five provinces, with different transmission intensities: Huambo, Cabinda, Uíge, Kwanza Norte, and Malanje. The detection of the mutations in pfdhfr and pfdhps genes was carried out in 452 P. falciparum blood samples by PCR RFLP. Results For pfdhfr gene, 90,3% of the samples carried the mutation 51I, with 7.5% of mixed infections; 51% carried wild type allele 59C, with 29.2% mixed infections and; 99.1% of isolates harboured the mutant allele 108N. Concerning, pfdhps gene, 83,1% were mutant type 437G with 11% mixed infections , while 87% of the studied isolates were wild type for codon 540. Discussion This is the first representative epidemiological study of the whole Angola country on the prevalence of the genotypes associated with SP chemoresistance. A high frequency of individual mutations in both genes (51I and 108N in pfdhfr, and 437G in pfdhps) was found, besides a low prevalence of the quintuple mutation. Conclusion The data showed that the implementation IPT using SP in children needs to be reviewed.
Malaria Journal. 01/2011;
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ABSTRACT: Malaria is the major cause of morbidity and mortality in Angola. The most vulnerable groups to Plasmodium falciparum infection are pregnant women and children under five years of age. The use of an intermittent preventive treatment (IPT) with sulphadoxine/pyrimethamine (SP) in pregnant women was introduced in Angola in 2006 by the National Malaria Control Programme, and currently this strategy has been considered to be used for children malaria control. Considering the previous wide use of SP combination in Angola, together to the reported cases of SP treatment failure it is crucial the evaluation of the prevalence of five mutations in pfdhfr and pfdhps genes associated to P. falciparum resistance to SP before the introduction of S/P IPT in children.
The study was conducted in five provinces, with different transmission intensities: Huambo, Cabinda, Uíge, Kwanza Norte, and Malanje. The detection of the mutations in pfdhfr and pfdhps genes was carried out in 452 P. falciparum blood samples by PCR RFLP.
For pfdhfr gene, 90,3% of the samples carried the mutation 51I, with 7.5% of mixed infections; 51% carried wild type allele 59C, with 29.2% mixed infections and; 99.1% of isolates harboured the mutant allele 108N. Concerning, pfdhps gene, 83,1% were mutant type 437G with 11% mixed infections , while 87% of the studied isolates were wild type for codon 540.
This is the first representative epidemiological study of the whole Angola country on the prevalence of the genotypes associated with SP chemoresistance. A high frequency of individual mutations in both genes (51I and 108N in pfdhfr, and 437G in pfdhps) was found, besides a low prevalence of the quintuple mutation.
The data showed that the implementation IPT using SP in children needs to be reviewed.
Malaria Journal 01/2011; 10(1):22. · 3.19 Impact Factor
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David Albuquerque,
Licínio Manco,
Kovana M Loua,
Ana Paula Arez,
Maria de Jesus Trovoada,
Luís Relvas,
Tamba S Millimono,
Silvia L Rath, Dinora Lopes,
Fátima Nogueira,
Luís Varandas,
Manuela Alvarez,
M Letícia Ribeiro
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ABSTRACT: Ferroportin is a transmembrane protein responsible for iron export from enterocytes and macrophages. Mutation c.744G → T (Q248H), located in exon 6 of the ferroportin gene SLC40A1, is found as a polymorphism in populations of African origin. This mutation has been extensively analysed in African-Americans, but poorly studied in native African populations.
To increase information about Q248H mutation frequency in native sub-Saharan populations examining three West African populations.
Samples from S. Tomé e Príncipe (n = 115), Angola (n = 156) and Republic of Guinea (n = 170) were analysed for Q248H mutation and for two polymorphisms, IVS1( - 24)G → C and microsatellite (CGG)(n), using standard molecular methodology.
The estimated frequencies of Q248H allele were 2.2% in S. Tomé e Príncipe, 3.5% in Angola and 4.1% in Republic of Guinea. Analysis of polymorphisms IVS1( - 24)G → C and (CGG)(n) showed mutation allele c.744T to be strongly associated with haplotype IVS1( - 24)G/(CGG)(7).
This study confirmed the presence of Q248H mutation at polymorphic frequencies in three native sub-Saharan populations. Analysis of two additional markers in the same gene support a single origin of the mutant allele c.744T in the haplotype background IVS1( - 24)G/(CGG)(7).
Annals of Human Biology 01/2011; 38(3):378-81. · 1.98 Impact Factor
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ABSTRACT: Karavilagenin C (1), a cucurbitane-type triterpenoid, previously isolated from the aerial parts of Momordica balsamina, was acylated with different alkanoyl, aroyl and cinnamoyl chlorides/anydrides, yielding ten new mono or diesters, karavoates F (7) and H-P (8-16). Furthermore, the new compound cucurbalsaminol C (17) was isolated from the same plant. Their structures were assigned by spectroscopic methods, including 2D NMR experiments. Compounds 1 and 17 and the acyl derivatives 8-16 along with other five esters (2-6, karavoates A-E), previously prepared from 1, were evaluated for their in vitro antimalarial activity against the chloroquine-sensitive (3D7) and the chloroquine-resistant (Dd2) strains of Plasmodium falciparum. Compound 1 exhibited a moderate activity and 17 was inactive. However, a remarkable antiplasmodial activity was observed for most of karavilagenin C alkanoyl and monoaroyl/cynamoyl derivatives. Karavoates B, D, E, I, and M were the most active, displaying IC(50) values similar to those found for chloroquine, particularly against the resistant strain (IC(50) <0.6μM). Structure-activity relationships (SAR) are discussed. Moreover, the preliminary toxicity toward human cells of compounds 1-17 was also evaluated in breast cancer cell line (MCF-7). Most of the esters showed no toxicity, displaying, in general, much higher selectivity index values than those obtained for the parent compound.
Bioorganic & medicinal chemistry 01/2011; 19(1):330-8. · 2.82 Impact Factor
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João Lavrado,
Kaamil Gani,
Pedro A Nobre,
Sofia A Santos,
Paula Figueiredo, Dinora Lopes,
Virgílio do Rosário,
Jiri Gut,
Philip J Rosenthal,
Rui Moreira,
Alexandra Paulo
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ABSTRACT: Quindolone derivatives, designed to target the malaria parasite digestive vacuole and heme detoxification pathway, have been synthesized by reaction with 2-chloro-N,N-diethylethanamine. This reaction gave N,O-, N,N- and O-alkylated products containing one or two basic side-chains. The compounds were evaluated for antiplasmodial activity against the chloroquine-resistant Plasmodium falciparum W2 strain and for cytotoxicity in HepG2 A16 hepatic cells. By incorporating alkylamine side chains and chlorine atoms in the quindolone nucleus we transformed the inactive tetracyclic parent quindolones into moderate or highly active and selective antimalarial compounds. The most active and selective compound, 5c, showed an IC(50)=51 nM for P. falciparum and a selectivity ratio of 98.
Bioorganic & medicinal chemistry letters 10/2010; 20(19):5634-7. · 2.65 Impact Factor
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ABSTRACT: Bioassay-guided fractionation of the methanol extract of Momordica balsamina led to the isolation of three new cucurbitane-type triterpenoids, balsaminols C-E (1-3). Their structures were elucidated on the basis of spectroscopic methods including 2D NMR experiments (COSY, HMQC, HMBC and NOESY). Balsaminols C-E, together with ten cucurbitacins isolated from the same plant (4-13), were evaluated for their antimalarial activity against the Plasmodium falciparum chloroquine-sensitive strain 3D7 and the chloroquine-resistant clone Dd2. Most of the compounds displayed antimalarial activity. Compounds 9 and 12 revealed the highest antiplasmodial effects against both strains (IC50 values: 4.6, and 7.4 microM, 3D7, respectively; 4.0, and 8.2 microM, Dd2, respectively). Structure-activity relationships are discussed. Furthermore, the preliminary toxicity toward human cells of compounds 1-5 and 9 was investigated in breast cancer cell line (MCF-7). Compounds were inactive or showed weak toxicity (IC50 values>19.0).
Bioorganic & medicinal chemistry 07/2010; 18(14):5254-60. · 2.82 Impact Factor
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ABSTRACT: Abstract
Background
Plasmodium falciparum , has developed resistance to many of the drugs in use. The recommended treatment policy is now to use drug combinations. The atovaquone-proguanil (AP) drug combination, is one of the treatment and prophylaxis options. Atovaquone (ATQ) exerts its action by inhibiting plasmodial mitochondria electron transport at the level of the cytochrome bc1 complex. Plasmodium falciparum in vitro resistance to ATQ has been associated with specific point mutations in the region spanning codons 271-284 of the cytochrome b gene. ATQ -resistant Plasmodium yoelii and Plasmodium berghei lines have been obtained and resistant lines have amino acid mutations in their CYT b protein sequences. Plasmodium chabaudi model for studying drug-responses and drug-resistance selection is a very useful rodent malaria model but no ATQ resistant parasites have been reported so far. The aim of this study was to determine the ATQ sensitivity of the P. chabaudi clones, to select a resistant parasite line and to perform genotypic characterization of the cytb gene of these clones.
Methods
To select for ATQ resistance, Plasmodium. chabaudi chabaudi clones were exposed to gradually increasing concentrations of ATQ during several consecutive passages in mice. Plasmodium chabaudi cytb gene was amplified and sequenced.
Results
ATQ resistance was selected from the clone AS-3CQ. In order to confirm whether an heritable genetic mutation underlies the response of AS-ATQ to ATQ, the stability of the drug resistance phenotype in this clone was evaluated by measuring drug responses after (i) multiple blood passages in the absence of the drug, (ii) freeze/thawing of parasites in liquid nitrogen and (iii) transmission through a mosquito host, Anopheles stephensi . ATQ resistance phenotype of the drug-selected parasite clone kept unaltered. Therefore, ATQ resistance in clone AS-ATQ is genetically encoded. The Minimum Curative Dose of AS-ATQ showed a six-fold increase in MCD to ATQ relative to AS-3CQ.
Conclusions
A mutation was found on the P. chabaudi cytb gene from the AS-ATQ sample a substitution at the residue Tyr268 for an Asn, this mutation is homologous to the one found in P. falciparum isolates resistant to ATQ.
Malaria Journal. 01/2010;
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ABSTRACT: Plasmodium falciparum, has developed resistance to many of the drugs in use. The recommended treatment policy is now to use drug combinations. The atovaquone-proguanil (AP) drug combination, is one of the treatment and prophylaxis options. Atovaquone (ATQ) exerts its action by inhibiting plasmodial mitochondria electron transport at the level of the cytochrome bc1 complex. Plasmodium falciparum in vitro resistance to ATQ has been associated with specific point mutations in the region spanning codons 271-284 of the cytochrome b gene. ATQ -resistant Plasmodium yoelii and Plasmodium berghei lines have been obtained and resistant lines have amino acid mutations in their CYT b protein sequences. Plasmodium chabaudi model for studying drug-responses and drug-resistance selection is a very useful rodent malaria model but no ATQ resistant parasites have been reported so far. The aim of this study was to determine the ATQ sensitivity of the P. chabaudi clones, to select a resistant parasite line and to perform genotypic characterization of the cytb gene of these clones.
To select for ATQ resistance, Plasmodium. chabaudi chabaudi clones were exposed to gradually increasing concentrations of ATQ during several consecutive passages in mice. Plasmodium chabaudi cytb gene was amplified and sequenced.
ATQ resistance was selected from the clone AS-3CQ. In order to confirm whether an heritable genetic mutation underlies the response of AS-ATQ to ATQ, the stability of the drug resistance phenotype in this clone was evaluated by measuring drug responses after (i) multiple blood passages in the absence of the drug, (ii) freeze/thawing of parasites in liquid nitrogen and (iii) transmission through a mosquito host, Anopheles stephensi. ATQ resistance phenotype of the drug-selected parasite clone kept unaltered. Therefore, ATQ resistance in clone AS-ATQ is genetically encoded. The Minimum Curative Dose of AS-ATQ showed a six-fold increase in MCD to ATQ relative to AS-3CQ.
A mutation was found on the P. chabaudi cytb gene from the AS-ATQ sample a substitution at the residue Tyr268 for an Asn, this mutation is homologous to the one found in P. falciparum isolates resistant to ATQ.
Malaria Journal 01/2010; 9:135. · 3.19 Impact Factor
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ABSTRACT: Malaria is the infectious disease causing the highest morbidity and mortality in Angola and due to widespread chloroquine (CQ) resistance, the country has recently changed its first-line treatment recommendations for uncomplicated malaria, from CQ to artemisinin combination therapies (ACT) in adults, and sulphadoxine/pyrimethamine (S/P) in pregnant women. Loss of SP sensitivity is, however, progressing rapidly in Africa and, in this study, were investigated a number of molecular markers associated to CQ and S/P.
Blood samples were collected from 245 children with uncomplicated malaria, admitted at the Pediatric Hospital Dr. David Bernardino (HPDB), Angola, and the occurrence of mutations in Plasmodium falciparum was investigated in the pfmdr1 (N86Y) and pfcrt (K76T) genes, associated with CQ resistance, as well as in pfdhfr (C59R) and pfdhps (K540E), conferring SP resistance.
The frequencies of pfmdr1 mutations in codon 86 were 28.6% N, 61.3% Y and 10.1% mixed infections (NY). The frequency of pfcrt mutations in codon 76 were 93.9% K, 5.7% T and 0.4% mixed infections (KT). For pfdhfr the results were in codon 59, 60.6% C, 20.6% R and 18.8% mixed infections (CR). Concerning pfdhps, 6.3% of the isolates were bearers of the mutation 540E and 5.4% mixed infections (K540E).
The results of this epidemiologic study showed high presence of CQ resistance markers while for SP a much lower prevalence was detected for the markers under study.
Malaria Journal 12/2008; 7:236. · 3.19 Impact Factor
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ABSTRACT: Population samples from Angola, Mozambique, and S. Tomé e Príncipe were screened for the TPI gene promoter variants -5A-->G, -8G-->A and -24T-->G. Three haplotypes were identified in the three populations: the haplotype -5A-8G-24T (average frequency 65.3%) and two less common haplotypes -5G-8G-24T (average frequency 24.7%) and -5G-8A-24T (average frequency 10.0%). A population sample from Central Portugal showed the haplotype -5A-8G-24T in 139 chromosomes and one subject heterozygous for haplotype -5G-8A-24G. The exact test of sample differentiation among three groups of malaria-infected individuals classified according to the severity of the disease showed no significant differences. We confirmed TPI gene diversity in sub-Saharan Africa, but we could not detect any association between TPI promoter variation and a malarial protective effect. Larger scale epidemiological studies are thus required to clarify this putative mechanism of natural host defense against this worldwide public health problem.
American Journal of Human Biology 10/2008; 21(1):118-20. · 2.27 Impact Factor
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ABSTRACT: The dichloromethane, methanol and aqueous ethanol extracts of the stem bark of Pycnanthus angolensis were evaluated for their in vitro activity against the 3D7 Plasmodium falciparum strain. The CH (2)Cl (2) extract was the most active showing an IC (50) = 1.6 microg/mL. From this extract, a new dibenzylbutane lignan, threo-4,4'-dihydroxy-3-methoxylignan ( 1) named pycnantolol, together with the known lignans (-)-dihydroguaiaretic acid ( 2), heliobuphthalmin ( 3), talaumidin ( 4), hinokinin ( 5), the labdane-type diterpene ozic acid ( 6), and the steroids stigmast-4-en-6beta-ol-3-one ( 7), beta-sitosterol ( 8) and stigmasterol ( 9) were isolated. Their structures were established on the basis of physical and spectroscopic methods, including 2 D NMR experiments (COSY, HMQC, HMBC and NOESY). The antimalarial activity of compounds 1 - 7 was evaluated against 3D7 and Dd2 P. falciparum strains. Despite the significant activity displayed by the crude CH (2)Cl (2) extract, the isolated compounds showed weaker antiplasmodial activity. The lowest IC (50) value was obtained for talaumidin ( 4) (IC (50) = 20.7 microg/mL against the Dd2-chloroquine resistant P. falciparum strain).
Planta Medica 08/2008; 74(11):1408-12. · 2.15 Impact Factor
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ABSTRACT: The present investigation was carried out to identify and study the gene expression patterns of two novel Plasmodium falciparum Multidrug Resistance associated Protein (MRP) transporters belonging to the ABC protein family coded by the genes pfmrp1 and pfmrp2 in P. falciparum. Full sequencing resulted in the identification of four SNPs in pfmrp1 and eight SNPs and three insertions/deletions in pfmrp2. Both genes showed different patterns of expression along the intraerythrocytic cycle, pfmrp1 peaks at the late trophozoites/early schizont stage, while pfmrp2 is transcribed, mostly during the ring stage and peaks again towards the end of the cycle, suggesting different parasite physiological functions. Higher levels of pfmrp1 and pfmrp2 gene expression were observed in chloroquine and mefloquine treated cultures, more visible with mefloquine. These results suggest a possible involvement of pfmrp1 and pfmrp2 genes in P. falciparum drug response.
Journal of Cell and Animal Biology. 02/2008; 2:10-20.
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ABSTRACT: Abstract
Background
Malaria is the infectious disease causing the highest morbidity and mortality in Angola and due to widespread chloroquine (CQ) resistance, the country has recently changed its first-line treatment recommendations for uncomplicated malaria, from CQ to artemisinin combination therapies (ACT) in adults, and sulphadoxine/pyrimethamine (S/P) in pregnant women. Loss of SP sensitivity is, however, progressing rapidly in Africa and, in this study, were investigated a number of molecular markers associated to CQ and S/P.
Methods
Blood samples were collected from 245 children with uncomplicated malaria, admitted at the Pediatric Hospital Dr. David Bernardino (HPDB), Angola, and the occurrence of mutations in Plasmodium falciparum was investigated in the pfmdr1 (N86Y) and pfcrt (K76T) genes, associated with CQ resistance, as well as in pfdhfr (C59R) and pfdhps (K540E), conferring SP resistance.
Results
The frequencies of pfmdr1 mutations in codon 86 were 28.6% N, 61.3% Y and 10.1% mixed infections (NY). The frequency of pfcrt mutations in codon 76 were 93.9% K, 5.7% T and 0.4% mixed infections (KT). For pfdhfr the results were in codon 59, 60.6% C, 20.6% R and 18.8% mixed infections (CR). Concerning pfdhps , 6.3% of the isolates were bearers of the mutation 540E and 5.4% mixed infections (K540E).
Conclusion
The results of this epidemiologic study showed high presence of CQ resistance markers while for SP a much lower prevalence was detected for the markers under study.
Malaria Journal. 01/2008;
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ABSTRACT: The synthesis and antimalarial properties of twelve new chlorinated 9H-xanthones, carrying a [2-(diethylamino)ethyl]amino group in position 1, are reported. All compounds were found to be active towards the chloroquine-susceptible and chloroquine-resistant strains 3D7 and Dd2, resp., of the protozoa parasite Plasmodium falciparum. Especially one compound, 6-chloro-1-{[2-(diethylamino)ethyl]amino}-9H-xanthen-9-one (1k), was found to exhibit significant in vitro activity (IC50 = 3.9 microM) towards the resistant Dd2 strain.
Chemistry & Biodiversity 08/2007; 4(7):1508-19. · 1.80 Impact Factor
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ABSTRACT: To evaluate the basal in vitro responses of Plasmodium falciparum isolates collected in The Democratic Republic of São Tomé and Príncipe to artemether (ATH), artesunate (ATN) and amodiaquine (AMQ).
The prevalence of given single nucleotide polymorphisms in the pfmdr1, pfcrt, pftctp and pfATPase6 genes was assessed by PCR-RFLP or DNA sequencing, and gene copy numbers were estimated by real-time PCR.
Mean IC50s to ATH and ATN were relatively low (1.12 nm and 0.58 nm, respectively). However, 10% of parasites displayed AMQ IC50 values above the accepted resistance threshold of 60 nm and there was a positive association between susceptibility to all three drugs (ATH vs. ATN: R = 0.84; ATH vs. AMQ: R = 0.68; ATN vs. AMQ: R = 0.72). Mutations in the pfcrt and pfmdr1 genes were highly prevalent, while only one synonymous polymorphism was detected in the pfATPase6 gene and no mutations were found in pftctp. All isolates harboured a single copy of the genes studied.
Artemisinin combination treatment in the São Tomé and Príncipe should be efficacious, although a significant number of AMQ-resistant parasites were detected and the susceptibility to each drug was positively associated with that of the other two. Mutations in the pfcrt and pfmdr1 genes are near fixation, most likely because of high levels of chloroquine resistance, whereas only one protein type of the artemisinin resistance candidate, PfATPase6, was identified.
Tropical Medicine & International Health 04/2007; 12(3):353-62. · 2.80 Impact Factor
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ABSTRACT: The increasing levels of Plasmodium falciparum resistance to chloroquine (CQ) in Thailand have led to the use of alternative antimalarials, which are at present also becoming ineffective. In this context, any strategies that help improve the surveillance of drug resistance, become crucial in overcoming the problem.
In the present study, we have established the in vitro sensitivity to CQ, mefloquine (MF), quinine (QUIN) and amodiaquine (AMQ) of 52 P. falciparum isolates collected in Thailand, and assessed the prevalence of four putative genetic polymorphisms of drug resistance, pfcrt K76T, pfmdr1 N86Y, pfmdr1 D1042N and pfmdr1 Y1246D, by PCR-RFLP.
The percentage of isolates resistant to CQ, MF, and AMQ was 96% (50/52), 62% (32/52), and 58% (18/31), respectively, while all parasites were found to be sensitive to QUIN. In addition, 41 (79%) of the isolates assayed were resistant simultaneously to more than one drug; 25 to CQ and MF, 9 to CQ and AMQ, and 7 to all three drugs, CQ, MF and AMQ. There were two significant associations between drug sensitivity and presence of particular molecular markers, i) CQ resistance / pfcrt 76T (P = 0.001), and ii) MF resistance / pfmdr1 86N (P < 0.001)
i) In Thailand, the high levels of CQ pressure have led to strong selection of the pfcrt 76T polymorphism and ii) pfmdr1 86N appears to be a good predictor of in vitro MF resistance.
Malaria Journal 11/2002; 1:12. · 3.19 Impact Factor
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ABSTRACT: Abstract
Background
The increasing levels of Plasmodium falciparum resistance to chloroquine (CQ) in Thailand have led to the use of alternative antimalarials, which are at present also becoming ineffective. In this context, any strategies that help improve the surveillance of drug resistance, become crucial in overcoming the problem.
Methods
In the present study, we have established the in vitro sensitivity to CQ, mefloquine (MF), quinine (QUIN) and amodiaquine (AMQ) of 52 P. falciparum isolates collected in Thailand, and assessed the prevalence of four putative genetic polymorphisms of drug resistance, pfcrt K76T, pfmdr1 N86Y, pfmdr1 D1042N and pfmdr1 Y1246D, by PCR-RFLP.
Results
The percentage of isolates resistant to CQ, MF, and AMQ was 96% (50/52), 62% (32/52), and 58% (18/31), respectively, while all parasites were found to be sensitive to QUIN. In addition, 41 (79%) of the isolates assayed were resistant simultaneously to more than one drug; 25 to CQ and MF, 9 to CQ and AMQ, and 7 to all three drugs, CQ, MF and AMQ. There were two significant associations between drug sensitivity and presence of particular molecular markers, i) CQ resistance / pfcrt 76T ( P = 0.001), and ii) MF resistance / pfmdr1 86N ( P < 0.001)
Conclusions
i) In Thailand, the high levels of CQ pressure have led to strong selection of the pfcrt 76T polymorphism and ii) pfmdr1 86N appears to be a good predictor of in vitro MF resistance.
Malaria Journal. 01/2002;
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ABSTRACT: Developing countries, where malaria is endemic, depend strongly on traditional medicine as a source for inexpensive treatment of this disease. However, scientific data to validate the antimalarial properties of these herbal remedies are scarce. Consequently, it is important that antimalarial medicinal plants are investigated, in order to establish their efficacy and to determine their potential as sources of new antimalarial drugs. In this study, we evaluated the claimed antimalarial properties of fifty eight crude extracts from fifteen plants used in traditional medicine against malaria and fever, mainly from Southern African regions. The air-dried powdered plant parts (roots, leaves, seeds or bark) or whole plants were extracted, sequentially, with solvents of increased polarity (n-hexane, dichloromethane, ethyl acetate and methanol). Schizontocidal activity was measured using a standard in vitro assay, with 3D7 Plasmodium falciparum strain. From the 58 extracts tested, two of them showed a significant activity (IC 50 < 5 µg/mL), and 34.5 % showed a moderate activity (10 < IC 50 < 50 µg/mL). A bioassay-guided fractionation of the most active extracts is ongoing.
