Antiplasmodial and antipyretic studies on root extracts of Anthocleista djalonensis against Plasmodium berghei

ObjectiveTo evaluate the antimalarial activities of ethanolic root extract/fractions of Anthocleista djalonensis (A. djalonensis) in Plasmodium berghei (P. berghei) infected mice.MethodsA. djalonensis root extract (175–1 000 mg/kg) and fractions (chloroform, ethyl acetate and methanol; 250 and 500 mg/kg) were investigated for antiplasmodial activity against chloroquine-sensitive Plasmodium berghei infections in mice and for antipyretic activity against dinitrophenol, amphetamine and yeast-induced pyrexia. The antiplasmodial activity during early and established infections as well as prophylactic were investigated. Artesunate (5 mg/kg) and pyrimethamine (1.2 mg/kg) were used as positive controls. Antipyretic activity of the crude extract was also evaluated against dinitrophenol, amphetamine and yeast-induced pyrexia.ResultsThe extract and its fractions dose-dependently reduced parasitaemia induced by chloroquine sensitive Plasmodium berghei infection in prophylactic, suppressive and curative models in mice. These reductions were statistically significant (P<0.001). They also improved the mean survival time from 13 to 28 days relative to control (P<0.001). The activities of extract/fractions were comparable to that of the standard drugs used (chloroquine and pyrimethamine). On pyrexia induced by dinitrophenol, amphetamine and yeast, the extract inhibited significantly (P<0.05 – 0.001) and in a dose-dependent fashion temperature rise caused by these pyrogens.ConclusionsA. djalonensis root extract has antiplasmodial and antipyretic activities which may in part be mediated through the chemical constituents of the plant.     

Antimalarial potency of the methanol leaf extract of Maerua crassifolia Forssk (Capparaceae)

ObjectiveTo investigate the in vivo antiplasmodial effect of methanol leaf extract of Maerua crassifolia in mice infected with chloroquine sensitive Plasmodium berghei berghei.MethodsThe extract was evaluated for activity against early infection, curative effect against established infection at dose levels of 100, 200 and 400 mg/kg p.o. Chloroquine at 10 mg/kg was used as standard drug.ResultsA dose dependent chemo-suppression of the parasites was obtained at different dose levels of the extract tested with a considerable mean survival time.ConclusionsThe results support continued investigation of components of traditional medicines as potential new antimalarial agents.     

Antimalarial activity of Ageratum conyzoides in combination with chloroquine and artesunate

ObjectiveTo determine the suppressive and curative activity of aqueous leaf extract of Ageratum conyzoides (A. conyzoides) in combination with chloroquine and artesunate, respectively against Plasmodium berghei infection in mice.MethodsUsing malaria (Plasmodium berghei) infected albino mice of both sexes, aqueous extracts of A. conyzoides in combination with chloroquine and artesunate were tested for antimalarial activity, respectively. Four-day suppressive test and Rane's curative test were carried out.ResultsSuppressive tests showed significant dose dependent reduction in parasitemia level produced by the extract-chloroquine and extract-artesunate combinations. Suppressive activities of both extract-drug combinations were greater than the individual drugs alone. Extract-chloroquine (100:5) produced the highest suppressive effect (98% suppression). Curative tests showed absolute survival in two extract-drug combinations. Two extract-drug combinations produced higher curative effects than the individual drugs alone. The highest dose combinations of extract-chloroquine (100:5) and extract-artesunate (100:5) produced absolute parasitemia clearance (cure) in the infected mice.ConclusionsThe study indicated that aqueous extract of A. conyzoides had the ability to potentiate the antimalarial activity of chloroquine and artesunate against induced plasmodiasis in mice. It contributes a lot in the malaria endemic and poverty stricken tropics.     

Evaluation of the antimalarial potential of Icacina senegalensis Juss (Icacinaceae)

ObjectiveTo evaluate in vivo antimalarial activity of methanol leaf extract of Icacina senegalensis.MethodsThe extract was investigated for activity against early and established malaria infections using Swiss albino mice infected with Plasmodium berghei at dose levels of 25, 50 and 100 mg/kg. Chloroquine (10 mg/kg) was used as positive control.ResultsA dose dependent chemo-suppression of the parasites was observed at different dose levels of the extract tested with a considerable mean survival time.ConclusionsThe results support further investigation on components of traditional medicines as potential new antimalarial agents.     

Antimalarial potential of kolaviron,a biflavonoid from Garcinia kola seeds,against Plasmodium berghei infection in Swiss albino mice

Objective:To investigate the antimalarial potential of kolaviron(KV),a biflavonoid fraction from Garcinia kola seeds,against Plasmodium berghei(P.berghei)infection in Swiss albino mice.Methods:The study consists of seven groups of ten mice each.Groups I,II and III were normal mice that received com oil.KV1 and chloroquine(CQ),respectively.Groups IV,V,ⅥandⅦwere infected mice that received corn oil.CQ,KYI and KV2.respectively.CQ.KY1 and KV2were given at 10-,100-and 200-mg/kg daily,respectively for three consecutive days.Results:Administration of KV1 and KV2 significantly(P0.05)suppressed P.berghei-infection in the mice by 85%and 90%.respectively,while CQ produced 87%suppression relative to untreated infected group after the fifth day of treatment.Also,KV2 significantly(P0.05)increased the mean survival time of the infected mice by 175%.The biflavonoid prevented a drastic reduction in HCV from day4 of treatment,indicating its efficacy in ameliorating anaemia.Significant(P0.05)oxidative stress assessed by the elevation of serum and hepatic malondialdehydewere observed in unlrealed P.berghei-infected mice.Specifically,senum and hepatic malondialdehyde levels increased by93%and 78%,resjiectively in the unlrealed infecled mice.Furlhennore,antioxidant indices,viz;superoxide dismutase.catalase,glutathione-s-transferasc.glualhione peroxidase and reduced gluathione decreased significantly(P0.05)in the tissues of untreated P.berghei-infected mice.KV significantly(P0.05)ameliorated the P.berghei-induced decrease in antioxidant status of the infected mice.Conclusions:This study shows that kolaviron,especially at 200 mg/kg,has high antimalarial activities in P.berghei-infected mice,in addition to its known antioxidant properties.     

In vitro and In vivo Antimalarial Activity of Amphiphilic Naphthothiazolium Salts with Amine-Bearing Side Chains

Because of emerging resistance to existing drugs, new chemical classes of antimalarial drugs are urgently needed. We have rationally designed a library of compounds that were predicted to accumulate in the digestive vacuole and then decrystallize hemozoin by breaking the iron carboxylate bond in hemozoin. We report the synthesis of 16 naphthothiazolium salts with amine-bearing side chains and their activities against the erythrocytic stage of Plasmodium falciparum in vitro. KSWI-855, the compound with the highest efficacy against the asexual stages of P. falciparum in vitro, also had in vitro activity against P. falciparum gametocytes and in vivo activity against P. berghei in a murine malaria model.     

In vivo antiplasmodial activities of ethanolic extract and fractions of Eleucine indica

ObjectiveTo evaluate the in vivo antiplasmodial activities of the extract and fractions (n-hexane, chloroform, ethylacetate, butanol, aqueous) of the whole plant in Plasmodium berghei berghei infected mice.MethodsOral administrations of the extract (200, 400, and 600 mg/kg) of Eleucine indica and fractions (400 mg/kg) were screened in the 4-day, repository and curative tests. Chloroquine (5 mg/kg), pyrimethamine (1.2 mg/kg) and artesunate (5 mg/kg) were used as controls.ResultsThe extract showed significant (P< 0.05–0.001) dose-dependent, antiplasmodial activity in the 4-day, repository and curative tests and increased the survival times of the infected mice. All the fractions exhibited significant antiplasmodial activity with the highest being ethylacetate fraction.ConclusionsEleucine indica extract and fractions possess antimalarial activity which confirms the ethnobotanical use of this plant as a malarial remedy and opens a new highway to further investigate its potentials in the on-going fight against malaria.     

Sulfadoxine-pyrimethamine resistance in Plasmodium falciparum: A zoomed image at the molecular level within a geographic context

Antimalarial chemotherapy is one of the main pillars in the prevention and control of malaria. Following widespread resistance of Plasmodium falciparum to chloroquine, sulfadoxine-pyrimethamine came to the scene as an alternative to the cheap and well-tolerated chloroquine. However, widespread resistance to sulfadoxine-pyrimethamine has been documented. In vivo efficacy tests are the gold standard for assessing drug resistance and treatment failure. However, they have many disadvantages, such as influence of host immunity and drug pharmacokinetics. In vitro tests of antimalarial drug efficacy also have many technical difficulties. Molecular markers of resistance have emerged as epidemiologic tools to investigate antimalarial drug resistance even before becoming clinically evident. Mutations in P. falciparum dihydrofolate reductase and dihydrofolate synthase have been extensively studied as molecular markers for resistance to pyrimethamine and sulfadoxine, respectively. This review highlights the resistance of P. falciparum at the molecular level presenting both supporting and opposing studies on the utility of molecular markers.     

Polymorphisms of the oxidant enzymes glutathione S–transferase and glutathione reductase and their association with resistance of Plasmodium falciparum isolates to antimalarial drugs

ObjectiveTo investigate the association between amplification of the two regulatory genes controlling glutathione (GSH) levels, glutathione reductase (PfGR) and glutathione S-transferase (PfGST) genes and sensitivity of Plasmodium falciparum (P. falciparum) isolates collected from different malaria endemic areas of Thailand to standard antimalarial drugs.MethodsA total of 70 P. falciparum isolates were collected from endemic areas of multi-drug resistance (Tak, Chantaburi and Ranong Provinces) during the year 2008-2009. The in vitro assessment of antimalarial activity of P. falciparum clones (K1- and Dd 2 chloroquine resistant and 3D7-chloroquine sensitive) and isolates to chloroquine, quinine, mefloquine and arteusnate was performed based on SYBR Green modified assay.Results68 (97.14%), 11 (15.71%) and 28 (40%) isolates respectively were classified as chloroquine-, quinine- and mefloquine-resistant isolates. With this limited number of P. falciparum isolates included in the analysis, no significant association between amplification of PfGST gene and sensitivity of the parasite to chloroquine, quinine, mefloquine and quinine was found. Based on PCR analysis, Dd2, K1 and 3D7 clones all contained only one copy of the PfGST gene. All isolates (70) also carried only one copy number of PfGST gene. There appears to be an association between amplification of PfGR gene and chloroquine resistance. The 3D7 and Dd2 clones were found to carry only one PfGR gene copy, whereas the K1 clone carried two gene copies.ConclusionsChloroquine resistance is likely to be a consequence of multi-factors and enzymes in the GSH system may be partly involved. Larger number of parasite isolates are required to increase power of the hypothesis testing in order to confirm the involvement of both genes as well as other genes implicated in glutathione metabolism in conferring chloroquine resistance.     

Antiplasmodial and analgesic activities of Clausena anisata

ObjectiveAntiplasmodial and analgesic activities of the leaf extract and fractions of Clausena anisata (C. anisata) were evaluated for antimalarial and analgesic activities.MethodsThe crude leaf extract (39–117 mg/kg) and fractions (chloroform and acqeous; 78 mg/kg) of C. anisata were investigated for antiplasmodial activity against chloroquine-sensitive Plasmodium berghei (P. berghei) infections in mice using suppressive, prophylactic and curative models and analgesic activity against acetic acid, formalin and heat-induced pains. Artesunate, 5 mg/kg and pyrimethamine, 1.2 mg/kg were used as positive controls. Thin films made from tail blood of each mouse were used to assess the level of parasitaemia of the mice.ResultsThe extract and its fractions dose-dependently reduced parasitaemia induced by chloroquine-sensitive P. berghei in prophylactic, suppressive and curative models in mice. These reductions were statistically significant (P<0.001). They also improved the mean survival time (MST) from 17 to 21 days relative to control (P<0.01 ? 0.001). On chemically and thermally-induced pains, the extract inhibited acetic acid and formalin-induced inflammation as well as hot plate-induced pain in mice. These inhibitions were statistically significant (P<0.001) and in a dose-dependent fashion.ConclusionsThe antiplasmodial and analgesic effects of this plant may in part be mediated through its chemical constituents and it can be concluded that the C. anisata possess significant antimalarial and analgesic properties.     

In vitro antiplasmodial activity of marine sponge Clathria vulpina extract against chloroquine sensitive Plasmodium falciparum

ObjectiveTo explore the antiplasmodial potential of marine sponge Clathria vulpina (C. vulpina) against chloroquine sensitive Plasmodium falciparum (P. falciparum).MethodsThe marine sponge C. vulpina was collected from Thondi coast, authenticated and subjected for extraction by soaking in ethanol:water mixture (3:1 ratio). The percentage of extract was calculated. Filter sterilized extracts (100, 50, 25, 12.5, 6.25, 3.125 μg/mL) were screened for antiplasmodial activity against chloroquine sensitive P. falciparum. The extract was also tested for its hemolytic activity.ResultsThe percentage yield of extract of C. vulpina was found to be 4.8%. The crude extract of C. vulpina showed excellent antiplasmodial activity (IC₅₀=14.75 μg/mL) which was highly comparable to the positive control chloroquine (IC₅₀=7 μg/mL). Statistical analysis reveals that the significant antiplasmodial activity (P<0.05) was observed between the concentrations and the time of exposure. The chemical injury to erythrocytes was also carried out, which showed that there were no morphological changes in erythrocytes by the ethanolic extracts of sponges after 48 h of incubation. The extract showed slight hemolytic activity which almost equal to chloroquine at 100 μg/mL concentration (1.023%).ConclusionsThe marine sponge C. vulpina can be used as a putative antiplasmodial drug after completing successful clinical trials.     

酮替芬和赛庚啶增强体外培养的恶性疟原虫氯喹抗性株对氯喹反应性的研究

目的 研究酮替芬和赛庚啶增强体外培养的恶性疟原虫氯喹抗性株对氯喹反应性，及其增效机制。 方法 恶性疟原虫氯喹抗性株(Fcc SM1/yN株)取自云南省思茅地区恶性疟患者静脉血，经同步化处理，用新鲜血将红细胞感染率调至0.5%～1.0%，红细胞压积与培养基体积比(红细胞比容)为1 ∶ 9，混匀。制备氯喹药板及氯喹/酮替芬（或氯喹/赛庚啶）组合药板。氯喹药板自上而下每行氯喹终浓度依次为0.312 5～2 560 nmol/L，呈2倍递增。氯喹/酮替芬（或氯喹/赛庚啶）组合药板，是在氯喹药板基础上加入酮替芬（或赛庚啶），每行10孔自左至右终浓度依次为9.77～5 000 nmol/L，呈2倍递增, 每块药板均设A行空白对照。每孔加混匀血样 50 μl，37 ℃ 培养 34 h，镜检计数每200个疟原虫中含3个核以上裂殖体数，计算氯喹单药及各配伍组对恶性疟原虫的半数抑制浓度（IC₅₀），以及酮替芬（或赛庚啶）提高氯喹活性的指数（AEI）。选择AEI值较高的配伍组，进行增效时序性研究。当氯喹对虫体作用 0～10 h 分别加入酮替芬（或赛庚啶），34 h后检测和计算各时间段IC₅₀及AEI。选择氯喹/酮替芬（或氯喹/赛庚啶）最佳配伍剂量，培养恶性疟原虫 20 h，提取总RNA，用实时荧光定量PCR(real-time PCR)分析药物作用前后恶性疟原虫氯喹抗性转移基因（pfcrt）和多药抗性基因（pfmdr1）表达水平。 结果 0.312 5～2 560 nmol/L氯喹与625 nmol/L 酮替芬（或赛庚啶）配伍，增效作用显著，氯喹/酮替芬的IC50为74.53 nmol/L，AEI为0.42；氯喹/赛庚啶的IC50为89.70 nmol/L、AEI为0.30。5 nmol/L氯喹作用 6～7 h 加入625 nmol/L酮替芬（或赛庚啶），增效作用显著，氯喹/酮替芬的IC50为 67.70 nmol/L、AEI为0.47；氯喹/赛庚啶的IC₅₀为81.53 nmol/L、AEI为0.37。5 nmol/L氯喹与625 nmol/L酮替芬（或赛庚啶）配伍，作用20 h，氯喹/酮替芬可使pfcrt基因表达水平升高91%，而氯喹/赛庚啶可使pfmdr1 基因表达水平下降14%。 结论 体外氯喹与适量的酮替芬（或赛庚啶）配伍，能增强恶性疟原虫氯喹抗性株对氯喹的反应性。氯喹对虫体作用 6～7 h 加入酮替芬（或赛庚啶）增效作用显著。该增效作用与pfcrt基因和pfmdr1 基因的表达水平有关。     

Antimalarial potency of the leaf extract of Aspilia africana (Pers.) C.D. Adams

ObjectiveTo investigate the antimalarial activity of ethanol extract of Aspilia africana (A. africana) leaf.MethodsThe ethanol extract of A. africana leaf (100–400 mg/kg) was screened for blood schizonticidal effect against chloroquine-sensitive Plasmodium berghei (P. berghei) in mice both in early and established models of antimalarial studies.ResultsThe leaf extract exhibited significant (P<0.05) antiplasmodial activity in 4-day early infection and in established infection tests with a considerable mean survival time comparable to that of standard drug, chloroquine (10 mg/kg).ConclusionsThe findings show that ethanol extract of A. africana leaf possesses potent antiplasmodial activity which justify the use in ethnomedicine and can be developed in malaria therapy.     

Antimalarial and analgesic activities of ethanolic leaf extract of Panicum maximum

ObjectiveTo evaluate antiplasmodial and analgesic activities of ethanolic leaf extract/fractions of Panicum maximum.MethodsThe crude leaf extract (47–190 mg/kg) and fractions (chloroform, ethyl acqeous and methanol; 96 mg/kg) of Panicum maximum were investigated for antiplasmodial activity against chloroquine sensitive Plasmodium berghei infections in mice and for analgesic activity against chemical and heat-induced pains. The antiplasmodial activity during early and established infections as well as prophylactic were investigated. Artesunate at 5 mg/kg and pyrimethamine at 1.2 mg/kg were used as positive controls. Analgesic activity of the crude extract/fractions was also evaluated against acetic acid, formalin and heat-induced pains.ResultsThe extract and its fractions dose-dependently reduced parasitaemia induced by chloroquine sensitive Plasmodium berghei infection in prophylactic, suppressive and curative models in mice. These reductions were statistically significant (P<0.001). They also improved the mean survival time from 13 to 28 days compared with control (P<0.001). The activities of extract/fractions were incomparable to that of the standard drugs (Artesunate and pyrimethamine). On chemically and thermally-induced pains, the extract inhibited acetic acid and formalin-induced inflammation as well as hot plate-induced pain in mice. These inhibitions were statistically significant (P<0.001) and in a dose-dependent fashion.ConclusionsPanicum maximum leaf extract has antiplasmodial and analgesic activities which may in part be mediated through the chemical constituents of the plant.     

我国恶性疟原虫对氯喹抗性的消长

目的　监测停止或减少使用氯喹防治恶性疟后恶性疟原虫对氯喹抗性的变化。　方法　采用世界卫生组织 (WHO)制定的体外微量法和体内四周法 ,在停用氯喹后不同时间测定恶性疟原虫对氯喹的敏感性。　结果　海南省乐东县抱由镇体外法测定抗性率由 1981年的 97.9%降至 1997年的 2 6.7% (P <0.0 1) ,完全抑制裂殖体形成的平均药浓度由 10.46±7.14 pmol/μl 血 降至 1.63± 1.47pmol/μl 血 (P<0.0 1) ,用较高药浓度 (>6.4pmol/μl血)才能完全抑制裂殖体形成的病例所占比例由 83.3 %降为 6.7% (P<0.0 1)。体内法测定抗性率由 1981年的 84.2 %降为 1997年的 18.4% (P<0.0 1) ,三级抗性 (RⅢ )占抗性病例的比例由 5 3.1%降为 14.3 % (P<0.0 1) ,血中无性体疟原虫平均消失时间由 72.0± 2 1.6 h变为 5 0.7± 16.1 h。2 0 0 1年三亚市雅亮乡体外法测定抗性率为 5 9.8% ,平均抑制药浓度 3.5 6± 2.12 pmol/μl 血 。 2 0 0 3年乐东县福抱乡体内法测定抗性率为 62.5 % ,RI、RⅡ和RⅢ分别占抗性病例 50 %、30 %和 20 % ,无性体疟原虫平均消失时间 5 6.9± 17.2 h。云南省勐腊县体外法测定抗性率由 1981年的97.4%降至 1999年的 77.8% (P <0.0 1) ,完全抑制裂殖体形成的平均药物浓度由 17.2± 12.6 pmol/μl血降至4.4±3.1 pmol/μl(P<0.01)。2002年景洪县体外法测定抗性率为70.4%，抑制裂殖体形成的平均药物浓度为4.0±3.3 pmol/μl 血。 结论 减少或停止使用氯喹后，我国恶性疟原虫对氯喹抗性呈降低趋势，逐渐恢复了对氯喹的敏感性。     

同位素微量试验法检测新化合物抗恶性疟原虫活性试验

将连续培养的恶性疟原虫克隆系Dd2和3D7用6%山梨醇作2次同步处理。处理后第2代原虫用健康人红细胞稀释至红细胞比容为2.5%、原虫血症为0.5%,并加入2 μCi/ml 8-³H-次黄嘌呤,利用同位素微量试验法检测20个新化合物的抗疟原虫活性。结果显示20个新化合物均无明显的抗疟原虫活性;对照药物氯喹和奎宁显示出良好的抗疟活性,表明同位素微量试验法是一个稳定、可靠的体外筛选新抗疟药的方法。     

Antipyretic and antimalarial activities of crude leaf extract and fractions of Enicostema littorale

ObjectiveTo evaluate the antiplasmodial and antipyretic activities of whole plant extract and fractions of Enicostemma littorale (E. littorale) for ascertaining the folkloric claim of its antimalarial and antipyretic activities.MethodsThe crude extract (260 – 780 mg/kg) and fractions (chloroform and acqeous; 520 mg/kg) of E. littorale were investigated for antiplasmodial activity against chloroquine-sensitive Plasmodium berghei (P. berghei) infections in mice and for antipyretic activity against dinitrophenol, amphetamine and yeast-induced pyrexia. The antiplasmodial activity during early and established infections as well as prophylactic were investigated. Artesunate (5 mg/kg) and pyrimethamine (1.2 mg/kg) were used as positive controls. Antipyretic activity of the crude extract was also evaluated against dinitrophenol, amphetamine and yeast-induced pyrexia.ResultsThe extract and fractions dose-dependently reduced parasitaemia induced by chloroquine-sensitive P. berghei infection in prophylactic, suppressive and curative models in mice. These reductions were statistically significant (P<0.001). They also improved the mean survival time from 11 to 27 days relative to control (P<0.01 – 0.001). The activities of extract/fractions were comparable to that of the standard drugs used (artesunate and pyrimethamine). On pyrexia induced by dinitrophenol, amphetamine and yeast, the extract caused inhibitions which were statistically significant (P<0.05 – 0.001) and in a dose-dependent fashion.ConclusionsThese plant extracts possess considerable antiplasmodial and antipyretic activities, which justify its use in ethnomedicine.     

Synthesis,biological evaluation and molecular docking studies of tricyclic guanidine derivatives for anti-malarial activity

IntroductionMalaria is the most lethal among the parasitic diseases and challenge for developing counties. Globally, an estimated 3.3 billion people were at risk of malaria in 2011, with populations living in sub-Saharan Africa having the highest risk of acquiring malaria. Malarial infection caused by P. falciparum is the most deadly form among all pathogens. Moreover, there has been rapid increase in resistance to drugs by P. falciparum. This resistance is considered because of emergence through mutation or biochemical changes in the active site of drug targets. The lactate dehydrogenase of P. falciparum (PfLDH) has been used since long time as a potential molecular drug target for malaria. The LDH plays role in the inter-conversion of pyruvate to lactate in the glycolysis cycle, which is required for energy production in living cells.Objectives1) Synthesis of tricyclic guanidine derivatives and biological evaluation against resistant strain of P. falciparum (Lactate Dehydrogenase Inhibitor). 2) Molecular docking of synthesized derivatives to understand mechanism of inhibition.MethodsWe have synthesized fifty tricyclic guanidine derivatives based on batzelladine K backbone. All synthesized compounds were evaluated for anti-malarial activity against chloroquine resistant strains of P. falciparum by using plasmodial LDH activity as measure of inhibition. To understand the mechanism of inhibition and to identify pharmacophore required for activity, the molecular docking of tricyclic guanidine compounds was performed using CDOCKER program in Discovery Studio suit 3.5.Results & DiscussionWe have obtained many potent inhibitors. The docking studies showed that there is very strong correlation between in silico and in vitro results. The most active compound was found to have least CDOCKER interaction energy (–43.25 kcal/mol). It showed hydrophobic interaction with Gly27, Ala98, Asp53 and Ile54 residues in the enzyme binding pocket similar to that of chloroquine.ConclusionThe synthesized derivatives are potent inhibitor of chloroquine-resistant PfLDH and act on same binding site to that of chloroquine. Based on these results, more potent inhibitor against P. falciparum can be designed.     

In vitro antiplasmodial activity and cytotoxicity of extracts and fractions of Vitex madiensis, medicinal plant of Gabon

Vitex madiensis Oliv. (Lamiaceae) is traditionally used to treat malaria symptoms in Haut‐Ogooué, Gabon. Leaves and stem barks extracts were obtained using dichloromethane (CH₂Cl₂), ethyl acetate (EtOAc) and methanol (MeOH) as extraction solvents and fractionated on silica gel column. The in vitro antiplasmodial activity of CH₂Cl₂, EtOAc and MeOH extracts and fractions was evaluated against the chloroquine‐resistant FCB strain and field isolates of Plasmodium falciparum using the DELI test. The cytotoxicity of the extracts was tested on MRC‐5 and THP1 cells using the tetrazolium salt MTT colorimetric assay, and the selectivity index (SI) of each extract was calculated. CH₂Cl₂ extract, the EA1 fraction from EtOAc extract of stem barks and cyclohexane (L_cycl), dichloromethane (L_DM) and butanol (L_but) fractions from MeOH/H₂O extract of leaves exhibited the highest in vitro antiplasmodial activity on FCB strain and field isolates (IC₅₀ from 0.53 to 4.87 μg/ml) with high selectivity index (of 20.15–1800). These data support the use of V. madiensis in malaria treatment along with continued investigations within traditional medicines in the search of new antimalarial agents. The EA1, C₆H₁₂ and CH₂Cl₂ fractions could be selected for future investigation or/and for the treatment of malaria symptoms after standardization.     

High prevalence of PfCRT K76T mutation in Plasmodium falciparum isolates in Ghana

Plasmodium falciparum has successfully developed resistance to almost all currently used antimalarials. A single nucleotide polymorphism in the P. falciparum chloroquine resistance transporter (Pfcrt) gene at position 76 resulting in a change in coding from lysine to threonine (K76T) has been implicated to be the corner stone of chloroquine resistance. Widespread resistance to chloroquine in endemic regions led to its replacement with other antimalarials. In some areas this replacement resulted in a reversion of the mutant T76 allele to the wild-type K76 allele. This study was conducted to determine the prevalence of the K76T mutation of the Pfcrt gene eight years after the ban on chloroquine sales and use. A cross-sectional study was conducted in 6 regional hospitals in Ghana. PCR-RFLP was used to analyse samples collected to determine the prevalence of Pfcrt K76T mutation. Of the 1318 participants recruited for this study, 246 were found to harbour the P. falciparum parasites, of which 60.98% (150/246) showed symptoms for malaria. The prevalence of the Pfcrt T76 mutant allele was 58.54% (144/246) and that of the K76 wild-type allele was 41.46% (102/246). No difference of statistical significance was observed in the distribution of the alleles in the symptomatic and asymptomatic participants (P = 0.632). No significant association was, again, observed between the alleles and parasite density (P = 0.314), as well as between the alleles and Hb levels of the participants (P = 0.254). Notwithstanding the decline in the prevalence of the Pfcrt T76 mutation since the antimalarial policy change in 2004, the 58.54% prevalence recorded in this study is considered high after eight years of the abolishment of chloroquine usage in Ghana. This is in contrast to findings from other endemic areas where the mutant allele significantly reduced in the population after a reduction chloroquine use.