@article { ISI:000319417100005, title = {Design, synthesis, structural characterization by IR, 1H, 13C, 15N, 2D-NMR, X-ray diffraction and evaluation of a new class of phenylaminoacetic acid benzylidene hydrazines as pfENR inhibitors}, journal = {Chemical Biology \& Drug Design}, volume = {81}, number = {6}, year = {2013}, month = {JUN}, pages = {715-729}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

Recent studies have revealed that plasmodial enoyl-ACP reductase (pfENR, FabI), one of the crucial enzymes in the plasmodial type II fatty acid synthesis II (FAS II) pathway, is a promising target for liver stage malaria infections. Hence, pfENR inhibitors have the potential to be used as causal malarial prophylactic agents. In this study, we report the design, synthesis, structural characterization and evaluation of a new class of pfENR inhibitors. The search for inhibitors began with a virtual screen of the iResearch database by molecular docking. Hits obtained from the virtual screen were ranked according to their Glide score. One hit was selected as a lead and modified to improve its binding to pfENR; from this, a series of phenylamino acetic acid benzylidene hydrazides were designed and synthesized. These molecules were thoroughly characterized by IR, 1H, 13C, 15N, 2D-NMR (COSY, NOESY, 1H-13C, 1H-15N HSQC and HMBC), and X-ray diffraction. NMR studies revealed the existence of conformational/configurational isomers around the amide and imine functionalities. The major species in DMSO solution is the E, E form, which is in dynamic equilibrium with the Z, E isomer. In the solid state, the molecule has a completely extended conformation and forms helical structures that are stabilized by strong hydrogen bond interactions, forming a helical structure stabilized by N-H...O interactions, a feature unique to this class of compounds. Furthermore, detailed investigation of the NMR spectra indicated the presence of a minor impurity in most compounds. The structure of this impurity was deduced as an imidazoline-4-one derivative based on 1H-13C and 1H-15H HMBC spectra and was confirmed from the NOESY spectra. The molecules were screened for in vitro activity against recombinant pfENR enzyme by a spectrophotometric assay. Four molecules, viz. 17, 7, 10, and 12 were found to be active at 7, 8, 10, and 12m concentration, respectively, showing promising pfENR inhibitory potential. A classification model was derived based on a binary QSAR approach termed recursive partitioning (RP) to highlight structural characteristics that could be tuned to improve activity.

}, keywords = {ADMET, docking, enoyl-ACP reductase, FabI, hydrogen bonding, NMR, phenylaminoacetic acid benzylidene hydrazine, Plasmodium falciparum, Plasmodium falciparum enoyl-ACP reductase, QSAR, recursive partitioning, X-ray diffraction}, issn = {1747-0277}, doi = {10.1111/cbdd.12118}, author = {Samal, Ramanuj P. and Khedkar, Vijay M. and Pissurlenkar, Raghuvir R. S. and Bwalya, Angela Gono and Tasdemir, Deniz and Joshi, Ramesh A. and Rajamohanan, P. R. and Puranik, Vedavati G. and Coutinho, Evans C.} } @article { ISI:000344866500012, title = {Antiplasmodial activity-aided isolation and identification of quercetin-4 {\textquoteleft}-methyl ether in chromolaena odorata leaf fraction with high activity against chloroquine-resistant plasmodium falciparum}, journal = {Parasitology Research }, volume = {113}, number = {12}, year = {2014}, month = {DEC}, pages = {4415-4422}, publisher = {SPRINGER}, type = {Article}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

The present study was undertaken to evaluate the antiplasmodial activity of Chromolaena odorata leaf extract and gradient fractions through in vivo and in vitro tests, aimed at identifying its antiplasmodial constituents. Sub-fractions obtained from the most active gradient fraction were further tested for cytotoxicity against THP-1 cells, chloroquine-sensitive (HB3) and chloroquine-resistant (FCM29) Plasmodium falciparum. Our results showed the dichloromethane gradient fraction was most effective, significantly (P\<0.05) suppressing infection by 99.46 \% at 100 mg/kg body weight. Amongst its 13 sub-fractions (DF1-DF13), DF11 was highly active, with IC50 of 4.8 and 6.74 mu g/ml against P. falciparum HB3 and FCM29, respectively. Cytotoxicity of DF11 was estimated to be above 50 mu g/ml, and its separation by column chromatography yielded a flavonoid which was characterized as 3, 5, 7, 3{\textquoteright} tetrahydroxy-4{\textquoteright}-methoxyflavone from its spectroscopic data. It significantly suppressed infection (65.43-81.48 \%) in mice at 2.5-5 mg/kg doses and compared favourably with the effects of chloroquine and artemisinin. It may therefore serve as a useful phytochemical and antiplasmodial activity marker of C. odorata leaves, which exhibit potential for development as medicine against malaria.

}, keywords = {malaria, Medicinal plant, Plasmodium falciparum, Toxicity}, issn = {0932-0113}, doi = {10.1007/s00436-014-4119-y}, author = {Ezenyi, I. C. and Salawu, O. A. and Kulkarni, R. and Emeje, Martins} } @article { ISI:000380565100006, title = {Virtual screening techniques to probe the antimalarial activity of some traditionally used phytochemicals}, journal = {Combinatorial Chemistry \& High Throughput Screening}, volume = {19}, number = {7}, year = {2016}, month = {JUL}, pages = {572-591}, publisher = {BENTHAM SCIENCE PUBL LTD}, address = {EXECUTIVE STE Y-2, PO BOX 7917, SAIF ZONE, 1200 BR SHARJAH, U ARAB EMIRATES}, abstract = {

Malaria parasites show resistance to most of the antimalarial drugs and hence developing antimalarials which can act on multitargets rather than a single target will be a promising strategy of drug design. Here we report a new approach by which virtual screening of 292 unique phytochemicals present in 72 traditionally important herbs is used for finding out inhibitors of plasmepsin-2 and falcipain-2 for antimalarial activity against P. falciparum. Initial screenings of the selected molecules by Random Forest algorithm model of Weka using the bioassay datasets AID 504850 and AID 2302 screened 120 out of the total 292 phytochemicals to be active against the targets. Toxtree scan cautioned 21 compounds to be either carcinogenic or mutagenic and were thus removed for further analysis. Out of the remaining 99 compounds, only 46 compounds offered drug-likeness as per the {\textquoteleft}rule of five{\textquoteright} criteria. Out of ten antimalarial drug targets, only two target proteins such as 3BPF and 3PNR of falcipain-2 and 1PFZ and 2BJU of plasmepsin-2 are selected as targets. The potential binding of the selected 46 compounds to the active sites of these four targets was analyzed using MOE software. The docked conformations and the interactions with the binding pocket residues of the target proteins were understood by {\textquoteleft}Ligplot{\textquoteright} analysis. It has been found that 8 compounds are dual inhibitors of falcipain-2 and plasmepsin-2, with the best binding energies. Compound 117 (6aR, 12aS)-12a-Hydroxy-9-methoxy-2,3-dimethylenedioxy-8-prenylrotenone (Usaratenoid C) present in the plant Millettia usaramensis showed maximum molecular docking score.

}, keywords = {ADME, malaria, Molecular docking, molecular operating environment, Plasmodium falciparum, virtual screening, weka}, issn = {1386-2073}, doi = {10.2174/1386207319666160420141200}, author = {Shibi, Indira G. and Aswathy, Lilly and Jisha, Radhakrishnan S. and Masand, Vijay H. and Gajbhiye, Jayant M.} } @article {46878, title = {Whole-cell phenotypic screening of medicines for malaria venture pathogen box identifies specific inhibitors of plasmodium falciparum late-stage development and egress}, journal = {Antimicrobial Agents and Chemotherapy}, volume = {64}, year = {2020}, month = {MAY}, pages = {e01802-19}, type = {Article}, abstract = {

We report a systematic, cellular phenotype-based antimalarial screening of the Medicines for Malaria Venture Pathogen Box collection, which facilitated the identification of specific blockers of late-stage intraerythrocytic development of Plasmodium falciparum. First, from standard growth inhibition assays, we identified 173 molecules with antimalarial activity (50\% effective concentration [EC50] \<= 10 mu M), which included 62 additional molecules over previously known antimalarial candidates from the Pathogen Box. We identified 90 molecules with EC50 of \<= 1 mu M, which had significant effect on the ring-trophozoite transition, while 9 molecules inhibited the trophozoite-schizont transition and 21 molecules inhibited the schizontring transition (with \>= 50\% parasites failing to proceed to the next stage) at 1 mu M. We therefore rescreened all 173 molecules and validated hits in microscopy to prioritize 12 hits as selective blockers of the schizont-ring transition. Seven of these molecules inhibited the calcium ionophore-induced egress of Toxoplasma gondii, a related apicomplexan parasite, suggesting that the inhibitors may be acting via a conserved mechanism which could be further exploited for target identification studies. We demonstrate that two molecules, MMV020670 and MMV026356, identified as schizont inhibitors in our screens, induce the fragmentation of DNA in merozoites, thereby impairing their ability to egress and invade. Further mechanistic studies would facilitate the therapeutic exploitation of these molecules as broadly active inhibitors targeting late-stage development and egress of apicomplexan parasites relevant to human health.

}, keywords = {DNA fragmentation, egress, Medicines for Malaria Venture, MMV, Pathogen Box, phenotypic screening, Plasmodium falciparum, schizonts, stage-specific inhibition}, issn = {0066-4804}, doi = {10.1128/AAC.01802-19}, author = {Patra, Alok Tanala and Hingamire, Tejashri and Belekar, Meenakshi A. and Xiong, Aoli and Subramanian, Gowtham and Bozdech, Zbynek and Preiser, Peter and Shanmugam, Dhanasekaran and Chandramohanadas, Rajesh} }