Plasmodium Falciparum NF54 Research Articles

Cu-catalyzed click reaction in synthesis of eugenol derivatives as potent antimalarial agents

Eugenol(1), a terpenoid found in Ocimum, has various biological activities. The present study aims at extraction, isolation of the plant secondary metabolite eugenol (1), it’s derivatisation and structure identification as bioactive molecules. Synthesis and antiplasmodial activity (in-vitro and in-vivo), of a series of fourteen novel eugenol-based 1,2,3-triazole derivatives was done in the present study. Derivatives 5a–5n showed good antimalarial activity against the strain Plasmodium falciparum NF54. Derivative 5 m, IC50 at 2.85 µM was found to be several times better than its precursor 1 (106.82 µM) whereas the derivative 5n showed three fold better activity than compound 1, in vitro. The structure-activity relationship of the synthesised compounds indicated that the presence of triazole ring in eugenol analogues is responsible for their good activity. Compound 5m, was further evaluated for in-vivo antimalarial activity which showed about 79% parasitemia suppression. It is the first report on antimalarial activity of triazole eugenol derivatives.

Tetrahydropyridinylidene ammonium salts with arylalkyl and diarylalkyl substitution and their antiprotozoal activity

Tetrahydropyridin-4-ylidene salts with benzyl and dibenzyl substitution showed good antiprotozoal activity. This paper reports the synthesis of analogues with longer side chains. They were investigated for their antiprotozoal activities as well as for their cytotoxicity using microplate assays. The most active compounds showed activity against Trypanosoma brucei rhodesiense in concentrations < 0.06 µM. A series of compounds was active against Plasmodium falciparum NF54 in low nanomolar concentration and exhibited outstanding selectivity. The influence of substitution pattern and chain length on the antiprotozoal potencies were analyzed and structure–activity relationships were given. New compounds were characterized by FT-IR, HRMS, and NMR spectroscopy.Graphical abstract

Phytoconstituents from Turraea obtusifolia and their antiplasmodial activity

Three new steroids, turranin M, N and O (1-3), together with four known limonoids, nymania 1 (4), rubralin B (5), aphapolynin C (6) and Trichillia substance Tr B (7), were isolated from the leaves of Turraea obtusifolia. Their chemical structures were elucidated using NMR and MS. Rubralin B (5) displayed good activity against the asexual parasites from the drug sensitive Plasmodium falciparum NF54 strain with an IC50 value of 3.47 µg/mL (4.57 µM), nymania 1 (4) showed a weak activity (IC50 13.36 µg/mL (19.40 µM)) and the rest of compounds had IC50 > 20 µg/mL.

Efficient Oxidative Dearomatisations of Substituted Phenols Using Hypervalent Iodine (III) Reagents and Antiprotozoal Evaluation of the Resulting Cyclohexadienones against T. b. rhodesiense and P. falciparum Strain NF54.

Quinones and quinols are secondary metabolites of higher plants that are associated with many biological activities. The oxidative dearomatization of phenols induced by hypervalent iodine(III) reagents has proven to be a very useful synthetic approach for the preparation of these compounds, which are also widely used in organic synthesis and medicinal chemistry. Starting from several substituted phenols and naphthols, a series of cyclohexadienone and naphthoquinone derivatives were synthesized using different hypervalent iodine(III) reagents and evaluated for their in vitro antiprotozoal activity. Antiprotozoal activity was assessed against Plasmodium falciparum NF54 and Trypanosoma brucei rhodesiense STIB900. Cytotoxicity of all compounds towards L6 cells was evaluated and the respective selectivity indices (SI) were calculated. We found that benzyl naphthoquinone 5c was the most active and selective molecule against T. brucei rhodesiense (IC50 = 0.08 μM, SI = 275). Furthermore, the antiprotozoal assays revealed no specific effects. In addition, some key physicochemical parameters of the synthesised compounds were calculated.

In Vitro and In Silico Potential Inhibitory Effects of New Biflavonoids from Ochna rhizomatosa on HIV-1 Integrase and Plasmodium falciparum

The aim of this study was to identify bioactive secondary metabolites from Ochna rhizomatosa with potential inhibitory effects against HIV and Plasmodium falciparum. A phytochemical study of O. rhizomatosa root barks resulted in the identification of three new biflavonoids (1–3), along with four known ones (4–7). Compound 7 (Gerontoisoflavone A) was a single flavonoid present in the rootbark of the plant and was used as a reference. Compound 1 (IC50 = 0.047 µM) was the only one with a noteworthy inhibitory effect against HIV-1 integrase in vitro. Chicoric acid (IC50 = 0.006 µM), a pure competitive inhibitor of HIV-1 integrase, was used as control. Compound 2 exhibited the highest antiplasmodial activity (IC50 = 4.60 µM) against the chloroquine-sensitive strain of Plasmodium falciparum NF54. Computational molecular docking revealed that compounds 1 and 2 had the highest binding score (−121.8 and −131.88 Kcal/mol, respectively) in comparison to chicoric acid and Dolutegravir (−116 and −100 Kcal/mol, respectively), towards integrase receptor (PDB:3LPT). As far as Plasmodium-6 cysteine s48/45 domain inhibition is concerned, compounds 1 and 2 showed the highest binding scores in comparison to chloroquine, urging the analysis of these compounds in vivo for disease treatment. These results confirm the potential inhibitory effect of compounds 1 and 2 for HIV and malaria treatment. Therefore, our future investigation to find inhibitors of these receptors in vivo could be an effective strategy for developing new drugs.

Antiplasmodial and antimycobacterial activities of crude and lead-like enhanced extracts from Namibian medicinal plants

Ethnopharmacological relevanceEight indigenous medicinal plants which are used traditionally for the treatment of tuberculosis (TB), malaria, and associated symptoms, were selected for this study. Aim of studyThe aim of this study was to evaluate the antiplasmodial and antimycobacterial activities of the organic and aqueous crude extracts of different plant parts, by comparing the activities of subfractions (lead-like enhanced [LLE] extracts and methanol fractions) prepared from the bioactive crude extracts. Materials & methodsCrude aqueous and organic extracts were prepared for 25 different plant parts obtained from eight plant species. In vitro antiplasmodial activity was evaluated using the parasite lactate dehydrogenase assay against chloroquine-sensitive Plasmodium falciparum NF54 and in vitro antimycobacterial activity determined against the Mycobacterium tuberculosis H37Rv-GFP strain in a standard broth microdilution assay. The bioactive crude extracts were subjected to solid phase extraction with Strata-X 33 μm reversed phase cartridges and eluted with 70:30 MeOH: H2O:1% trifluoroacetic acid to yield the LLE extract, followed by a methanol rinse, herein referred to as the MeOH fraction. Both fractions were evaluated for antiplasmodial and antimycobacterial activity. Proton nuclear magnetic resonance spectroscopy (1H-NMR) and ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) profiling of the crude and active fractions of the phytochemically unexplored Sarcocaulon marlothii Engl. were performed to aid the identification of a potential antiplasmodial lead compound. ResultsTen of the aqueous and organic crude extracts displayed antimycobacterial activity, with minimum inhibitory concentration (MIC90) values ranging from 9.9 to 86.8 μg/mL, and four crude extracts showed antiplasmodial activity with inhibitory concentration (IC50) values between 5.2 and 17.8 μg/mL. Although the stems of S. marlothii are traditionally used to treat TB and related symptoms, the two crude extracts displayed weak antimycobacterial activity (MIC90 > 100 μg/mL) while the crude organic extract displayed moderate antiplasmodial activity with an IC50 value of 8.8 μg/mL. None of the LLE extracts prepared from the ten antimycobacterial-active crudes displayed any significant activity (MIC90 > 125 μg/mL). In contrast, fractionation of three antiplasmodial-active, crude organic extracts yielded MeOH fractions which displayed a 2-fold to 19-fold increase in activity. The 1H-NMR profiles of the active MeOH fraction (IC50 4.3 μg/mL) of S. marlothii (organic, stem) revealed the likely presence of an unidentified trisubstituted cinnamic acid derivative as one of the major compounds and UPLC-MS/MS data provided additional evidence that the compound may be a hydroxycinnamic acid derivative. Unfortunately, owing to the paucity of the material obtained, we were unable to purify and unequivocally determine the structure of this active compound. ConclusionsThis is the first report on the phytochemical profiling of S. marlothii and, based on the antiplasmodial activity recorded, it merits an in-depth phytochemical analysis for the unequivocal characterization of a potential antiplasmodial lead compound. Results from this study lend support to the effectiveness of extract enrichment in combination with NMR fingerprinting for antiplasmodial lead identification.

Variation in terpenoids in leaves of Artemisia annua grown under different LED spectra resulting in diverse antimalarial activities against Plasmodium falciparum

BackgroundProductivities of bioactive compounds in high-value herbs and medicinal plants are often compromised by uncontrollable environmental parameters. Recent advances in the development of plant factories with artificial lighting (PFAL) have led to improved qualitative and/or quantitative production of bioactive compounds in several medicinal plants. However, information concerning the effect of light qualities on plant pharmaceutical properties is limited. The influence of three different light-emitting diode (LED) spectra on leaf fresh weight (FW), bioactive compound production and bioactivity of Artemisia annua L. against the malarial parasite Plasmodium falciparum NF54 was investigated. Correlation between the A. annua metabolites and antimalarial activity of light-treated plant extracts were also determined.ResultsArtemisia annua plants grown under white and blue spectra that intersected at 445 nm exhibited higher leaf FW and increased amounts of artemisinin and artemisinic acid, with enhanced production of several terpenoids displaying a variety of pharmacological activities. Conversely, the red spectrum led to diminished production of bioactive compounds and a distinct metabolite profile compared with other wavelengths. Crude extracts obtained from white and blue spectral treatments exhibited 2 times higher anti-Plasmodium falciparum activity than those subjected to the red treatment. Highest bioactivity was 4 times greater than those obtained from greenhouse-grown plants. Hierarchical cluster analysis (HCA) revealed a strong correlation between levels of several terpenoids and antimalarial activity, suggesting that these compounds might be involved in increasing antimalarial activity.ConclusionsResults demonstrated a strategy to overcome the limitation of A. annua cultivation in Bangkok, Thailand. A specific LED spectrum that operated in a PFAL system promoted the accumulation of some useful phytochemicals in A. annua, leading to increased antimalarial activity. Therefore, the application of PFAL with appropriate light spectra showed promise as an alternative method for industrial production of A. annua or other useful medicinal plants with minimal environmental influence.

Assessment of Plasmodium falciparum Infection and Fitness of Genetically Modified Anopheles gambiae Aimed at Mosquito Population Replacement

Genetically modified (GM) mosquitoes expressing anti-plasmodial effectors propagating through wild mosquito populations by means of gene drive is a promising tool to support current malaria control strategies. The process of generating GM mosquitoes involves genetic transformation of mosquitoes from a laboratory colony and, often, interbreeding with other GM lines to cross in auxiliary traits. These mosquito colonies and GM lines thus often have different genetic backgrounds and GM lines are invariably highly inbred, which in conjunction with their independent rearing in the laboratory may translate to differences in their susceptibility to malaria parasite infection and life history traits. Here, we show that laboratory Anopheles gambiae colonies and GM lines expressing Cas9 and Cre recombinase vary greatly in their susceptibility to Plasmodium falciparum NF54 infection. Therefore, the choice of mosquitoes to be used as a reference when conducting infection or life history trait assays requires careful consideration. To address these issues, we established an experimental pipeline involving genetic crosses and genotyping of mosquitoes reared in shared containers throughout their lifecycle. We used this protocol to examine whether GM lines expressing the antimicrobial peptide (AMP) Scorpine in the mosquito midgut interfere with parasite infection and mosquito survival. We demonstrate that Scorpine expression in the Peritrophin 1 (Aper1) genomic locus reduces both P. falciparum sporozoite prevalence and mosquito lifespan; both these phenotypes are likely to be associated with the disturbance of the midgut microbiota homeostasis. These data lead us to conclude that the Aper1-Sco GM line could be used in proof-of-concept experiments aimed at mosquito population replacement, although the impact of its reduced fitness on the spread of the transgene through wild populations requires further investigation.

Modifications and hybrids of 1,2,3,4-tetrahydropyridinium salts and their antiprotozoal potencies

The antiprotozoal activity of 1-benzyltetrahydropyridin-4-yliden iminium salts is reported. This paper describes the preparation of a series of analogs from dihydropyridines or dihydrothiopyrans as educts. The new compounds were investigated for their activity against Plasmodium falciparum NF54, a causative organism of Malaria tropica and Trypanosoma brucei rhodesiense, the causative organism of Human African Trypanosomiasis (sleeping sickness). Several structure–activity relationships were detected. Both the substituents in ring positions 1 and 4 of the tetrahydropyridinium moiety had a strong impact on the antiprotozoal activities as well as on the cytotoxicity of compounds against L-6 cells (rat skeletal myoblasts). All new compounds were characterized using FT-IR spectroscopy, HRMS, and NMR spectroscopy.Graphic abstract

8-Amino-6-Methoxyquinoline-Tetrazole Hybrids: Impact of Linkers on Antiplasmodial Activity.

A new series of compounds was prepared from 6-methoxyquinolin-8-amine or its N-(2-aminoethyl) analogue via Ugi-azide reaction. Their linkers between the quinoline and the tert-butyltetrazole moieties differ in chain length, basicity and substitution. Compounds were tested for their antiplasmodial activity against Plasmodium falciparum NF54 as well as their cytotoxicity against L-6-cells. The activity and the cytotoxicity were strongly influenced by the linker and its substitution. The most active compounds showed good activity and promising selectivity.

Search for the Active Ingredients from a 2-Aminothiazole DMSO Stock Solution with Antimalarial Activity.

Chemical decomposition of DMSO stock solutions is a common incident that can mislead biological screening campaigns. Here, we share our case study of 2‐aminothiazole 1, originating from an antimalarial class that undergoes chemical decomposition in DMSO at room temperature. As previously measured biological activities observed against Plasmodium falciparum NF54 and for the target enzyme PfIspE were not reproducible for a fresh batch, we tackled the challenge to understand where the activity originated from. Solvent‐ and temperature‐dependent studies using HRMS and NMR spectroscopy to monitor the decomposition led to the isolation and in vitro evaluation of several fractions against PfIspE. After four days of decomposition, we successfully isolated the oxygenated and dimerised compounds using SFC purification and correlated the observed activities to them. Due to the unstable nature of the two isolates, it is likely that they undergo further decomposition contributing to the overall instability of the compound.

Bioactive half-sandwich Rh and Ir bipyridyl complexes containing artemisinin

Reaction of dihydroartemisinin (DHA) with 4-methyl-4′-carboxy-2,2′-bipyridine yielded the new ester derivative L1. Six novel organometallic half-sandwich chlorido Rh(III) and Ir(III) complexes (1–6) containing pentamethylcyclopentadienyl, (Cp*), tetramethylphenylcyclopentadienyl (Cpxph), or tetramethylbiphenylcyclopentadienyl (Cpxbiph), and N,N-chelated bipyridyl group of L1, have been synthesized and characterized. The complexes were screened for inhibitory activity against the Plasmodium falciparum 3D7 (sensitive), Dd2 (multi-drug resistant) and NF54 late stage gametocytes (LSGNF54), the parasite strain Trichomonas vaginalis G3, as well as A2780 (human ovarian carcinoma), A549 (human alveolar adenocarcinoma), HCT116 (human colorectal carcinoma), MCF7 (human breast cancer) and PC3 (human prostate cancer) cancer cell lines. They show nanomolar antiplasmodial activity, outperforming chloroquine and artemisinin. Their activities were also comparable to dihydroartemisinin. As anticancer agents, several of the complexes showed high inhibitory effects, with Ir(III) complex 3, containing the tetramethylbiphenylcyclopentadienyl ligand, having similar IC50 values (concentration for 50% of maximum inhibition of cell growth) as the clinical drug cisplatin (1.06–9.23 μM versus 0.24–7.2 μM, respectively). Overall, the iridium complexes (1–3) are more potent compared to the rhodium derivatives (4–6), and complex 3 emerges as the most promising candidate for future studies.

Palladium-catalysed synthesis of arylnaphthoquinones as antiprotozoal and antimycobacterial agents.

Malaria and tuberculosis are still among the leading causes of death in low-income countries. The 1,4-naphthoquinone (NQ) scaffold can be found in a variety of anti-infective agents. Herein, we report an optimised, high yield process for the preparation of various 2-arylnaphthoquinones by a palladium-catalysed Suzuki reaction. All synthesised compounds were evaluated for their in-vitro antiprotozoal and antimycobacterial activity. Antiprotozoal activity was assessed against Plasmodium falciparum (P.f.) NF54 and Trypanosoma brucei rhodesiense (T.b.r.) STIB900, and antimycobacterial activity against Mycobacterium smegmatis (M.s.) mc2 155. Substitution with pyridine and pyrimidine rings significantly increased antiplasmodial potency of our compounds. The 2-aryl-NQs exhibited trypanocidal activity in the nM range with a very favourable selectivity profile. (Pseudo)halogenated aryl-NQs were found to have a pronounced effect indicating inhibition of mycobacterial efflux pumps. Cytotoxicity of all compounds towards L6 cells was evaluated and the respective selectivity indices (SI) were calculated. In addition, the physicochemical parameters of the synthesised compounds were discussed.

New 2-aminopyrimidine derivatives and their antitrypanosomal and antiplasmodial activities

Novel 2-aminopyrimidine derivatives were prepared from acyclic starting materials, benzylidene acetones and ammonium thiocyanates, via 5 steps, including ring closure, aromatization, S-methylation, oxidation to methylsulfonyl compounds, and formation of guanidines with suitable amines. The prepared compounds differ from each other by the substitutions of their amino group and of their phenyl ring. The 2-aminopyrimidines were tested by use of microplate assays for their in vitro activities against a causative organism of sleeping sickness, Trypanosoma brucei rhodesiense, as well as against a causative organism of malaria, Plasmodium falciparum NF54. Their cytotoxic properties were determined with L-6 cells (rat skeletal myoblasts). Some of the compounds exhibited quite good antitrypanosomal activity, and others showed excellent antiplasmodial activity. The influence of the structural modifications on these activities is discussed.Graphic abstract

Dimeric dehydroaporphinoids with antiplasmodial properties from the liana of Artabotrys aurantiacus (Annonaceae)

Abstract Artabotrys aurantiacus is a Cameroonian Medicinal plant used in traditional medicines to fight against Malaria. So far, there is no reported data on the chemical composition of this plant. From the CH2Cl2/MeOH (1:1) extract of the liana of A. aurantiacus, two new dimeric dehydroaporphine alkaloids, aurantiacine A (1) and B (2) were isolated along with nine known compounds. Their chemical structures were elucidated by means of HRESI-MSn and spectroscopic methods, including 1D and 2D NMR, and by comparison with data from the literature. The isolated compounds were evaluated for their anti-plasmodial activity in vitro against the erythrocytic stage of Plasmodium falciparum NF54. Compounds 1-4 displayed moderate anti-plasmodial properties with IC50 values of 0.6336, 0.1120, 0.2601 and 1.0159 μM respectively.

Antimycobacterial, antiplasmodial studies and cytotoxicity of oleanolic acid and its derivative from Syzygium aromaticum Linn (Myrtaceae)

Malaria and tuberculosis are among the most common death causes and threats to human life globally. In a quest to find new antimalarial and anti-mycobacterial drugs, oleanolic acid (OA) was isolated from the flower buds of Syzygium aromaticum Linn (Myrtaceae). The derivative, 3-O-Acetyl-Oleanolic acid (OAA), was synthesized from the isolated product and the biological activities of the two compounds were compared. The antiplasmodial and antimycobacterial activity of oleanolic acid and its derivative were investigated against Plasmodium falciparum (Chloroquine Sensitive Strain) NF54 and Mycobacterium tuberculosis H37Rv. OAA exhibited IC50 of 4.3 µg/ml against P. falciparum, compared with an IC50 of 27.4 µg/ml for OA, while against M. tuberculosis OAA showed 0.1 µg/ml, compared with an IC50 of 0.042 µg/ml for OA. In the cytotoxicity studies, using the MTT assay, both compounds exhibited LC50 of &gt; 300 µg/ml against both human embryonic kidney (HEK293) and hepatocellular carcinoma cell lines (HepG2), suggesting that the compounds are not cytotoxic at low to moderate concentrations against the tested cell lines. In conclusion, the derivative OAA improved the antiplasmodial activity but no improvement was shown for antimycobacterial activity, in comparison with the starting material OA. Thus, more derivatives could be designed, using OA as starting material, to obtain future antiplasmodial compounds.

Generation of Novel Plasmodium falciparum NF135 and NF54 Lines Expressing Fluorescent Reporter Proteins Under the Control of Strong and Constitutive Promoters

Transgenic reporter lines of malaria parasites that express fluorescent or luminescent proteins are valuable tools for drug and vaccine screening assays as well as to interrogate parasite gene function. Different Plasmodium falciparum (Pf ) reporter lines exist, however nearly all have been created in the African NF54/3D7 laboratory strain. Here we describe the generation of novel reporter lines, using CRISPR/Cas9 gene modification, both in the standard Pf NF54 background and in a recently described Cambodian P. falciparum NF135.C10 line. Sporozoites of this line show more effective hepatocyte invasion and enhanced liver merozoite development compared to Pf NF54. We first generated Pf NF54 reporter parasites to analyze two novel promoters for constitutive and high expression of mCherry-luciferase and GFP in blood and mosquito stages. The promoter sequences were selected based on available transcriptome data and are derived from two housekeeping genes, i.e., translation initiation factor SUI1, putative (sui1, PF3D7_1243600) and 40S ribosomal protein S30 (40s, PF3D7_0219200). We then generated and characterized reporter lines in the Pf NF135.C10 line which express GFP driven by the sui1 and 40s promoters as well as by the previously used ef1α promoter (GFP@ef1α, GFP@sui1, GFP@40s). The GFP@40s reporter line showed strongest GFP expression in liver stages as compared to the other two lines. The strength of reporter expression by the 40s promoter throughout the complete life cycle, including liver stages, makes transgenic lines expressing reporters by the 40s promoter valuable novel tools for analyses of P. falciparum.

A Clinical Trial to Evaluate Plasmodium Falciparum 7G8 and NF54 Challenge Strains (PfSPZ) in a Head-to-head Comparative Study - (ECG-CHMI)

A Clinical Trial to Evaluate Plasmodium Falciparum 7G8 and NF54 Challenge Strains (PfSPZ) in a Head-to-head Comparative Study - (ECG-CHMI)

Effects of Silver Nanoparticle from Dicoma anomala Sond. Root Extract on MCF-7 Cancer Cell Line and NF54 Parasite Strain: an In Vitro Study.

Biogenic silver nanoparticles (AgNPs) continue captivating researchers in biomedicine field of research. Dicoma anomala Sond. plant, locally known as hloenya, hlonya, maagbossie, inyongwana, is widely recommended by South African traditional health practitioners (THPs) to treat against different health issues. The antiplasmodial effects of novel sesquiterpene molecules (C30H36O7; MW: 509.25) isolated from D. anomala Sond. have been reported by us (Patent US 8,586,112 B2). The aim of the study was to determine the anticancer activity of AgNPs synthesized using D. anomala plant root extract and the antiparasitic potency of AgNP-conjugated sesquiterpene. Nanoparticles have been characterized using different methods. Anticancer activity of AgNPs was evaluated against the MCF-7. This study also revealed that the AgNP-conjugated sesquiterpene has shown better antiparasitic activity against Plasmodium falciparum NF54 strain. One-pot synthesized AgNPs using Dicoma anomala Sond. root extract caused oxidative damage in breast cancer cells. These findings indicate the need for more in-depth research in the use of the AgNPs and sesquiterpene for development into potential leads as an antimalarial candidates and to improve the bioavailability of these sesquiterpenes.

Safety, Immunogenicity, and Protective Efficacy of Radiation Attenuated Plasmodium Falciparum NF54 Sporozoites (PfSPZ Vaccine) During Malaria Transmission Season in Healthy African Adult Women of Childbearing Potential in Mali

Safety, Immunogenicity, and Protective Efficacy of Radiation Attenuated Plasmodium Falciparum NF54 Sporozoites (PfSPZ Vaccine) During Malaria Transmission Season in Healthy African Adult Women of Childbearing Potential in Mali