Plasmodium Falciparum 3D7 Strain Research Articles

Conformationally Restrained Aromatic Analogues of Fosmidomycin and FR900098

The synthesis and in-vitro antimalarial activity of conformationally restrained bis(pivaloyloxymethyl) ester analogues of the natural product fosmidomycin is presented. In contrast to alpha-aryl-substituted analogues, conformationally restrained aromatic analogues exhibit only moderate in-vitro antimalarial activity against the chloroquine-sensitive strain 3D7 of Plasmodium falciparum. The most active derivative displays an IC(50) value of 47 microM.

Comparative Kinomics of Plasmodium Organisms: Unity in Diversity

Phosphorylation by protein kinases is a very common and crucial process in many signal transduction pathways in eukaryotes. This review describes comparative protein kinase analysis of two apicomplexa Plasmodium falciparum (3D7 strain) and Plasmodium yoelii yoelii (17XNL strain) which are causative agents of malaria in human and African rat respectively. Sensitive bioinformatics techniques enable identification of 82 and 60 putative protein kinases in P. falciparum and P. yoelii yoelii respectively and these sequences could be classified into known subfamilies of protein kinases. The most populated kinase subfamilies in both the plasmodium species correspond to CAMK and CMGC groups. Analysis of domain architectures enables detection of uncommon domain organization in kinases of both the organisms such as kinase domain tethered to EF hands as well as PH domain. Components of MAPK signaling pathway is not well conserved in plasmodium organisms. Such observations suggest that plasmodium protein kinases are highly divergent from other eukaryotes. A transmembrane kinase with 6 membrane spanning segments in P. falciparum seems to have no orthologue in P. yoelii yoelii. 19 P. falciparum kinases have been found to cluster separately from P. yoelii yoelii kinases and hence these kinases are unique to P. falciparum genome. Only 28 orthologous pairs of kinases seem to be present between these two plasmodium organisms. Comparative kinome analysis of two plasmodium species has thus provided clues to the function of many protein kinases based upon their classification and domain organization and also implicate marked differences even between two plasmodium organisms.

α-Phenylethyl Substituted Bis(pivaloyloxymethyl) Ester Analogues of Fosmidomycin and FR900098

α-Phenylethyl substituted bis(pivaloyloxymethyl) ester analogues of the natural products Fosmidomycin and FR900098 have been synthesized, and their in vitro antimalarial activity determined. The α-phenylethyl substituted Fosmidomycin analogue displays moderate in vitro antimalarial activity against the chloroquine-sensitive strain 3D7 of Plasmodium falciparum.

Antimalarial Activity of Crambescidin 800 and Synthetic Analogues against Liver and Blood Stage of Plasmodium sp.

Structural features associated with the antimalarial activity of the marine natural product crambescidin 800 were studied using synthetic analogues of the related compound ptilomycalin A. The study suggests that the guanidine moiety is cytotoxic, whereas the spermidine-containing aliphatic chain increases activity. The most active analogue, compound 11, had in vitro activity against Plasmodium falciparum strain 3D7 (IC50=490 nM) that was stronger than the in vitro activity against murine L5178Y cells (IC50 = 8.5-59 microM). In vitro growth inhibition of liver stages of P. yoelii yoelii in mouse hepatocytes was observed (IC50 = 9.2 microM). The compound did not significantly prolong median survival time after a single subcutaneous administration of 80 mg/kg in P. berghei-infected mice. Compound 11 did not cause DNA fragmentation in an in vitro micronucleus assay.

Synthesis and antimalarial activity of chain substituted pivaloyloxymethyl ester analogues of Fosmidomycin and FR900098

Fosmidomycin is a promising antimalarial drug candidate with a unique chemical structure and a novel mode of action. Chain substituted pivaloyloxymethyl ester derivatives of Fosmidomycin and its acetyl analogue FR900098 have been synthesized and their in vitro antimalarial activity versus the Chloroquine sensitive strain 3D7 of Plasmodium falciparum has been determined.

Plasmodium research in the postgenomic era

The complete genomic sequence of Plasmodium falciparum strain 3D7 was published in October 2002. At the Next Steps in Malaria Research meeting in April 2005, the next practical steps were considered and the priorities ranked for postgenomic research in Plasmodium. The high-throughput approaches that will help to answer the major biological questions regarding Plasmodium should, like the genome project itself, build community-shared resources, and efforts must be made to help researchers ready themselves to use the tools that will become available.

Metalloantimalarials: Synthesis, X-ray crystal structure of potent antimalarial copper (II) complex of arylazo-4-hydroxy-1,2-naphthoquinone

The crystal structure of copper (II) complex of 3-arylazo-4-hydroxy-1,2-naphthoquinone is reported. The in vitro antimalarial activity of analogous compounds against Plasmodium falciparum 3D7 strain reveals correlation with metal redox couple, suggesting component of parasitic electron transport chain as a possible target.

Labdanes and isopimaranes from Platycladus orientalis and their effects on erythrocyte membrane and on Plasmodium falciparum growth in the erythrocyte host cells.

Six labdanes (1-6) and four isopimaranes (7-10), including three new natural products (7, 9, and 10), were isolated from Platycladus orientalis, and their structures determined using 1D and 2D NMR methods, ion-cyclotron resonance HRMS, and optical rotation data. Relative configurations of all chiral centers in the isopimaranes were determined using NOESY experiments at 600 and 800 MHz. Specific optical rotation data were used to correlate absolute configurations. Compounds 1-9 and aframodial (11) were tested for their in vitro antiplasmodial activity and for their ability to induce changes of erythrocyte shape in order to obtain data about possible correlation between the two effects. All compounds tested exhibited weak (IC(50) > 25 microM) in vitro antiplasmodial effects against Plasmodium falciparum strain 3D7. At the same time, the compounds caused echinocytic or stomatocytic changes of the erythrocyte membrane curvature, indicative of their incorporation into the lipid bilayer, in the concentration region where the antiplasmodial activity was observed. The antiplasmodial effect of these compounds thus appears to be an indirect effect on the erythrocyte host cell. Weak or moderate antiplasmodial activity observed with many other apolar natural products, in particular those with amphiphilic structures, is also likely to be an indirect effect.

Antiplasmodial constituents of Cajanus cajan

Bioactivity-guided fractionation of extracts of roots and leaves of Cajanus cajan afforded 8 compounds: betulinic acid, biochanin A, cajanol, genistein and 2'-hydroxygenistein, longistylin A and C, and pinostrobin. The two stilbenes, longistylin A and C, and betulinic acid showed a moderately high in vitro activity against the chloroquine-sensitive Plasmodium falciparum strain 3D7.

In vitro Plasmodium falciparum drug sensitivity assay: inhibition of parasite growth by incorporation of stomatocytogenic amphiphiles into the erythrocyte membrane.

Lupeol, which shows in vitro inhibitory activity against Plasmodium falciparum 3D7 strain with a 50% inhibitory concentration (IC50) of 27.7 +/- 0.5 microM, was shown to cause a transformation of the human erythrocyte shape toward that of stomatocytes. Good correlation between the IC50 value and the membrane curvature changes caused by lupeol was observed. Preincubation of erythrocytes with lupeol, followed by extensive washing, made the cells unsuitable for parasite growth, suggesting that the compound incorporates into erythrocyte membrane irreversibly. On the other hand, lupeol-treated parasite culture continued to grow well in untreated erythrocytes. Thus, the antiplasmodial activity of lupeol appears to be indirect, being due to stomatocytic transformation of the host cell membrane and not to toxic effects via action on a drug target within the parasite. A number of amphiphiles that cause stomatocyte formation, but not those causing echinocyte formation, were shown to inhibit growth of the parasites, apparently via a mechanism similar to that of lupeol. Since antiplasmodial agents that inhibit parasite growth through erythrocyte membrane modifications must be regarded as unsuitable as leads for development of new antimalarial drugs, care must be exercised in the interpretation of results of screening of plant extracts and natural product libraries by an in vitro Plasmodium toxicity assay.

Antiplasmodial activity of selected Sudanese medicinal plants with emphasis on Maytenus senegalensis (Lam.) Exell.

The antiplasmodial activity of plant extracts related to four families was tested on chloroquine sensitive strain 3D7 and chloroquine resistant strain Dd2 of Plasmodium falciparum. The methanolic extract of Harrisonia abyssinica (Simaroubaceae) inhibited Dd2 with IC 50 value of 4.7 μg/ml, while in 3D7, the IC 50 value was 10 μg/ml. Most of the plants from the family Meliaceae showed highly potent antiplasmodial activity against the two tested strains. Khaya senegalensis, Azadirachta indica and Trichilia emetica showed IC 50 values less than 5 μg/ml. The methanolic extract of Annona squamosa (Annonaceae) leaves showed high antiplasmodial activity with IC 50 values of 2 and 30 μg/ml on 3D7 and Dd2, respectively. While stem bark showed moderate activity with IC 50 values of 8.5 and 120 μg/ml on Dd2. Maytenus senegalensis ( Celastraceae) possessed IC 50 values of 3.9 on 3D7, 10 μg/ml on Dd2 and had no effect on lymphocyte proliferation even at the highest tested concentration; the IC 50 was greater than 100 μg/ml. Liquid-liquid separation of the methanolic extract of M. senegalensis revealed that the dichloromethane extract possessed an IC 50 value of only 2.1 μg/ml. Column fractionation of dichloromethane extract gave four fractions and fraction two showed an IC 50 value of 0.5 μg/ml. Preliminary phytochemical analysis of dichloromethane fraction revealed terpenoids and traces of phenolic principles but no alkaloid, tannins or flavonoids were detected.

Plasmodium falciparum:A Simple, Rapid Method for Detecting Parasite Clones in Microtiter Plates

Malaria is still one of the most important global infectious diseases. Emergence of drug resistance and a shortage of new efficient antimalarials continue to hamper a malaria eradication agenda. Malaria parasites are highly sensitive to changes in the redox environment. Understanding the mechanisms regulating parasite redox could contribute to the design of new drugs. Malaria parasites have a complex network of redox regulatory systems housed in their cytosol, in their mitochondrion and in their plastid (apicoplast). While the roles of enzymes of the thioredoxin and glutathione pathways in parasite survival have been explored, the antioxidant role of α-lipoic acid (LA) produced in the apicoplast has not been tested. To take a first step in teasing a putative role of LA in redox regulation, we analysed a mutant Plasmodium falciparum (3D7 strain) lacking the apicoplast lipoic acid protein ligase B (lipB) known to be depleted of LA. Our results showed a change in expression of redox regulators in the apicoplast and the cytosol. We further detected a change in parasite central carbon metabolism, with lipB deletion resulting in changes to glycolysis and tricarboxylic acid cycle activity. Further, in another Plasmodium cell line (NF54), deletion of lipB impacted development in the mosquito, preventing the detection of infectious sporozoite stages. While it is not clear at this point if the observed phenotypes are linked, these findings flag LA biosynthesis as an important subject for further study in the context of redox regulation in asexual stages, and point to LipB as a potential target for the development of new transmission drugs.

Structure and superstructure of Plasmodium falciparum subtelomeric regions

Walking and jumping procedures were employed to obtain a consensus map of the 35–40 kb subtelomeric region shared by many chromosomal extremities in Plasmodium falciparum strain 3D7, and to characterise the portions flanking the rep20 tract, which is known to contain tandemly repeated, apparently degenerate, 21-bp repeats. The borders of rep20 were shown to harbour short (possibly locally homogenised) patterns of non-degenerate 12-, 17-, 23- and 28-bp repeats. The central repetitious portion of the consensus map was estimated to be about 18 kb in length, and to be separated from the telomere by approx. 11 kb of non-repetitious sequence, maintained with high fidelity at different chromosomal ends. Several kilobases of similarly conserved, non-repetitious sequence flank rep20 on its proximal side. Computer analysis of the rep20 sequence suggested that a peculiar superhelical winding originates from the conservation of identical nucleotide groups in phase with the pitch of the double helix, overcoming the effect of repeat degeneration in other positions of the 21-bp unit.