Busseihydroquinones A–D from the Roots of <i>Pentas bussei</i>

Four new naphthohydroquinones, named busseihydroquinones A–D (<b>1</b>–<b>4</b>), along with a known homoprenylated dihydronaphthoquinone (<b>5</b>), were isolated from the CH₂Cl₂/MeOH (1:1) extract of the roots of <i>Pentas bussei</i>. Although the genus <i>Pentas</i> is frequently used by traditional healers for the treatment of malaria, only marginal activities against the chloroquine-sensitive (D6) and the chloroquine-resistant (W2) strains of <i>Plasmodium falciparum</i> were observed for the crude root extract and the isolated constituents of this plant

Median-joining network diagram for MS data.

<p>Diagram showing relationship of the different parasite generations in H63 parasite-line samples. The multilocus MS haplotypes profiles were constructed for each of the parasite generations using the 12 MS markers located across the <i>P</i>. <i>falciparum</i> genome. The 26 generations of the cultured <i>P</i>. <i>falciparum</i> field isolates analyzed formed 18 unique 12-loci microsatellite haplotypes. For allele sizes please refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143565#pone.0143565.s004" target="_blank">S4 Table</a>. Each circle in the network represents a unique MS haplotype with the size of the circle being proportional to the number of isolates showing that particular haplotype. The red dots are hypothetical median vectors generated by the software to connect existing haplotypes within the network with maximum parsimony.</p

Phylogeny tree diagram for SNP data.

<p>Phylogeny tree constructed using SNP haplotypes of samples in H63 parasite-line. The SNP haplotype profiles are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143565#pone.0143565.s003" target="_blank">S3 Table</a>. Bayesian algorithm was used to infer the number of genetically related clusters from the individual SNP haplotype profiles generated using the 30-drug resistance SNPs.</p

<i>In vitro</i> activities of drugs tested against <i>P</i>. <i>falciparum</i> 3D7 strain.

<p><i>In vitro</i> activities of drugs tested against <i>P</i>. <i>falciparum</i> 3D7 strain.</p

Target-similarity search using <i>Plasmodium falciparum</i> proteome identifies approved drugs with anti-malarial activity and their possible targets

<div><p>Malaria causes about half a million deaths annually, with <i>Plasmodium falciparum</i> being responsible for 90% of all the cases. Recent reports on artemisinin resistance in Southeast Asia warrant urgent discovery of novel drugs for the treatment of malaria. However, most bioactive compounds fail to progress to treatments due to safety concerns. Drug repositioning offers an alternative strategy where drugs that have already been approved as safe for other diseases could be used to treat malaria. This study screened approved drugs for antimalarial activity using an <i>in silico</i> chemogenomics approach prior to <i>in vitro</i> verification. All the <i>P</i>. <i>falciparum</i> proteins sequences available in NCBI RefSeq were mined and used to perform a similarity search against DrugBank, TTD and STITCH databases to identify similar putative drug targets. Druggability indices of the potential <i>P</i>. <i>falciparum</i> drug targets were obtained from TDR targets database. Functional amino acid residues of the drug targets were determined using ConSurf server which was used to fine tune the similarity search. This study predicted 133 approved drugs that could target 34 <i>P</i>. <i>falciparum</i> proteins. A literature search done at PubMed and Google Scholar showed 105 out of the 133 drugs to have been previously tested against malaria, with most showing activity. For further validation, drug susceptibility assays using SYBR Green I method were done on a representative group of 10 predicted drugs, eight of which did show activity against <i>P</i>. <i>falciparum</i> 3D7 clone. Seven had IC₅₀ values ranging from 1 μM to 50 μM. This study also suggests drug-target association and hence possible mechanisms of action of drugs that did show antiplasmodial activity. The study results validate the use of proteome-wide target similarity approach in identifying approved drugs with activity against <i>P</i>. <i>falciparum</i> and could be adapted for other pathogens.</p></div

Druggability indices of predicted <i>P</i>. <i>falciparum</i> drug targets.

<p>Druggability indices of predicted <i>P</i>. <i>falciparum</i> drug targets.</p

Details of approved drugs predicted to target <i>P</i>. <i>falciparum</i> proteins that have not been tested.

<p>Details of approved drugs predicted to target <i>P</i>. <i>falciparum</i> proteins that have not been tested.</p

Steps in the chemogenomics repositioning workflow and their corresponding results.

<p>The yellow boxes represent <i>P</i>. <i>falciparum</i> sequences, drug targets are shown in blue boxes and drugs in green. Excluded drugs and proteins target have red box outlines.</p

Comparison of conserved amino acid residues.

<p>(A) ConSurf server MSA results (color coded according to conservation scores) of the drug target, the human tubulin beta-1 (NCBI accession number NP_110400.1) is overlaid above its BLAST pair-wise alignment with its <i>P</i>. <i>falciparum</i> homolog (NCBI accession number XP_001347369.1). The percent of the shared conserved residues was then determined; (B) 3D molecular structure of the human tubulin beta-1 chain with residues color coded according to their conservations scores, this was part of the ConSurf server results.</p

IC₅₀ values of some previously tested approved drugs that were predicted to have antiplasmodial activity.

<p>IC₅₀ values of some previously tested approved drugs that were predicted to have antiplasmodial activity.</p