Plasmodium Falciparum 3D7 Strain Research Articles

In vitro antimalarial activity assay of Ashitaba Leaf ethanolic extract (Angelica keiskei)


 Introduction: The incidence of malaria is still very high in number in the world. Difficulty in treating malaria is caused by the resistance of malaria parasites to conventional drugs. An alternative treatment that can be used to treat malaria is to discover new drugs from natural ingredients. 
 Aim: This study aimed to determine the activity of the Ashitaba leaf ethanolic extract as an antimalarial drug to Plasmodium falciparum strain 3D7. 
 Methods: This study tested the activity of Ashitaba extract on the growth of P.falciparum in five concentrations, namely concentration of 0.01 ppm, 0.1 ppm, 1 ppm, 10 ppm, and 100 ppm. 
 Results: The test results showed that the highest inhibitory effect was found on the concentration of 100 ppm with percent inhibition of 79.47 ± 26.91%. The 50% inhibition to parasites showed the half maximal inhibitory concentration (IC50) value of 2.09 ppm, compared to the positive control of which the IC50 of chloroquine was 0.007 ppm. 
 Conclusion: Ashitaba leaf extract can be considered to have very active anti-malarial activity, because it has an IC50 value of less than 5 ppm.

Artocarpus sericicarpus stem bark contains antimalarial substances against Plasmodium falciparum.

The finding of alternative medicine for malarial treatment still has become a substantial demand. The plant is one of the potential sources of drugs, among other natural sources. Artocarpus species showed great potential as the antimalarial source. This study aims to obtain active antimalarial fractions from Artocarpus sericicarpus stem bark. Stem bark of A.sericicarpus was extracted by ultrasonic-assisted extraction method using n-hexane, dichloromethane, and methanol as solvents. Fractionation of dichloromethane extract was conducted by open column chromatography using octadecyl silica as a stationary phase and gradient acetonitrile-water as a mobile phase. The antimalarial activity was determined by lactate dehydrogenase (LDH) assay against Plasmodium falciparum 3D7 strain. A.sericicarpus n-hexane, dichloromethane, and methanol extracts were showed antimalarial activity with an IC50 value of >4, 2.11, and >4μg/mL, respectively. Fractionation of dichloromethane extract was obtained 13 fractions. Seven of the 13 fractions tested showed antimalarial activity. Fraction-6 performed the highest inhibition with an IC50 value of 1.53±0.04μg/mL. Phytochemistry screening revealed that Fraction-6 contains flavonoid, polyphenol, and terpenoid compounds that can take a role in its antimalarial activity. A.sericicarpus contains antimalarial substances mainly in Fraction-6, which strongly inhibited the growth of P.falciparum. The flavonoid, polyphenol, and terpenoid compounds were identified in Fraction-6, which need to be further isolated to obtain and elucidate the active antimalarial compounds.

Short Communication: In vitro antimicrobial and antimalarial screening of a crude extract of Streptomyces sp. AB8 isolated from Lapindo Mud Volcano Area, Sidoarjo, Indonesia

Abstract. Arifiyanto A, Setyaningrum E, Nukmal N, Aeny TN. 2021. Short Communication: In vitro antimicrobial and antimalarial screening of a crude extract of Streptomyces sp. AB8 isolated from Lapindo Mud Volcano Area, Sidoarjo, Indonesia. Biodiversitas 22: 2817-2823. Streptomyces is a potential bacterial genus that has been investigated extensively as a source of natural microbial compounds. Its potential metabolites have been widely developed for pharmaceutical, pathogen control, and other applications in agriculture. This study aimed to determine the ability of the Streptomyces sp AB8 crude extract in inhibiting Plasmodium and pathogenic microbes. Streptomyces was cultured on Gause synthetic media for 10 days. The fermented broth culture media has dissolved in a 1:1 mixture of ethyl acetate and methanol. Biochemical characterization of this isolate has carried out using the standard methods. In-vitro antimalarial activity assay was performed using a chloroquine-sensitive Plasmodium falciparum strain 3D7. Fresh type O-positive human erythrocytes were suspended at 4 percent hematocrit in a complete medium to maintain culture. The inhibitory concentration (IC50) was determined using probit analysis. The results showed the extract of Streptomyces sp. AB8 contains phenolic and alkaloids. Streptomyces sp. AB8 extract can inhibit Dickeya zeae N-Unila 5, Dickeya zeae N-Unila 10, Aspergillus sp IK3, and Escherichia coli growth. The results also showed that the ICs0 value of extract against P. falciparum 3D7 was 17.56 ug/mL. Further research was needed to determine the types of purified bioactive compounds and their bioactivity.

Antimalarial, Antioxidant, and Toxicological Evaluation of Extracts of Celtis africana, Grosseria vignei, Physalis micrantha, and Stachytarpheta angustifolia.

In many parts of the world, malaria undoubtedly poses a serious threat to health care systems. Malaria treatment has increasingly become complicated, primarily due to the emergence of widespread resistance of the malaria parasites to cheap and affordable malaria therapeutics. The use of herbal remedies to treat various ailments, including malaria and malaria-like ailments in Ghana is common. We herein report on the antiplasmodial and antioxidant activities as well as toxicological evaluation of four medicinal plants (Celtis africana, Grosseria vignei, Physalis micrantha, and Stachytarpheta angustifolia) commonly used to treat malaria in Ghana. Following Soxhlet extraction of plant samples in ethanol, extracts were screened against Plasmodium falciparum (3D7 strain) in an in vitro antiplasmodial assay. The phosphomolybdenum and DPPH (1, 1-diphenyl-2 picrylhydrazyl) assays were used to evaluate antioxidant activities while toxicity assessment was carried out in mice using the acute toxicity test and kidney and liver function tests. Extracts from Celtis africana and Physalis micrantha were very active towards the parasites with half-maximal inhibitory concentrations (IC50's) of 29.1 and 3.5 µg/mL, respectively. Extracts of Grosseria vignei and Stachytarpheta angustifolia were inactive, having IC50 values greater than 50 µg/mL. All extracts exhibited excellent total antioxidant capacities (>800 mg/g AAE) and good DPPH radical scavenging potential (IC50 range of 300–900 µg/mL). The median lethal dose (LD50) of all extracts in the toxicological evaluation was greater than 2000 mg/kg and there was no effect of extracts on the levels and activities of key biomarkers of liver and kidney function. The activities of these plants obtained in this study partly give credence to their folkloric use in herbal medicines and suggest that they could provide promising lead compounds for malaria drug discovery programs.

In Vitro Potently Active Anti-Plasmodium and Anti-Toxoplasma Mongolian Plant Extracts.

Malaria and toxoplasmosis are important public health diseases affecting millions of people and animals each year, and there is a continuing need for new and improved treatments for them. Plants have provided many opportunities for new drug leads in pharmacology. We examined 43 crude extracts from Mongolian plants for their activities against the Plasmodium falciparum 3D7 strain and the Toxoplasma gondii RH strain using aSYBR Green-based fluorescence assay and a fluorescence-based assay, respectively. The potential toxicity of these extracts was also assessed on human foreskin fibroblast cells (HFF) using a cell viability assay. From the initial screenings, 11 and 7 crude extracts were effective against T. gondii and P. falciparum, respectively, at 100µg/ml concentration (≥ 80% inhibition activity). The 50% cytotoxic concentrations of the extracts were estimated on HFF cells, and their 50% inhibitory concentrations (IC50s) were calculated. According to our lead criteria (selective index, SI; value ≥ 10), six plants (Galatella dahurica leaf + flower, Leonurus deminutus leaf + flower, Oxytropis trichophysa aerial part, Schultzia crinita whole plant, Leontopodium campestre root, Spirea salicifolia aerial part) inhibited P. falciparum growth at IC50 values of 5.99-64.15µg/ml (SI values: 10.11-17.02). Amaranthus retroflexus root was highly active against T. gondii (IC50, 19.89µg/ml; SI value, 38). This first observation of the anti-Plasmodium and anti-Toxoplasma activities of Mongolian plant extracts shows them to be interesting potential candidates for drug discovery.

Synthesis and Antimalarial Activity of 4-Methylaminoquinoline Compounds against Drug-Resistant Parasite.

A series of novel 4-aminoquinoline analogues bearing a methyl group at 4-aminoquinoline moiety were synthesized via a new and robust synthetic route comprising in situtert-butoxycarbonyl (Boc) deprotection–methylation cascade resulting in the corresponding N-methylated secondary amine using Red-Al and an efficient microwave-assisted strategy for the fusion of N-methylated secondary amine with 4-chloroquinoline nucleus to access the series of novel 4-N-methylaminoquinoline analogues. The new series of compounds were evaluated for their antimalarial activity in in vitro and in vivo models. Among 21 tested compounds, 9a–i have shown a half-maximal inhibitory concentration (IC50) value less than 0.5 μM (i.e., <500 nM) against both chloroquine-sensitive strain 3D7 and chloroquine-resistant strain K1 of Plasmodium falciparum with acceptable cytotoxicity. Based on the in vitro antimalarial activity, selected compounds were screened for their in vivo antimalarial activity against Plasmodium yoelii nigeriensis (a multidrug-resistant) parasite in Swiss mice. Most of the compounds have shown significant inhibition on day 4 post infection at the oral dose of 100 mg/kg. Compound 9a has shown 100% parasite inhibition on day 4, and out of five treated mice, two were cured till the end of the experiment. The present study suggests that 4-methylamino substitution is well tolerated for the antiplasmodial activity with reduced toxicity and therefore will be highly useful for the discovery of a new antimalarial agent against drug-resistant malaria.

Retraction Note: Antimalarial efficacy of Pongamia pinnata (L) Pierre against Plasmodium falciparum (3D7 strain) and Plasmodium berghei (ANKA)

The objective of the current study was to assess the in vitro antiplasmodial activities of leaf, bark, flower, and the root of Pongamia pinnata against chloroquine-sensitive Plasmodium falciparum (3D7 strain), cytotoxicity against Brine shrimp larvae and THP-1 cell line. For in vivo study, the plant extract which has shown potent in vitro antimalarial activity was tested against Plasmodium berghei (ANKA strain). The plant Pongamia pinnata was collected from the herbal garden of Acharya Nagarjuna University of Guntur district, Andhra Pradesh, India. Sequentially crude extracts of methanol (polar), chloroform (non-polar), hexane (non-polar), ethyl acetate (non-polar) and aqueous (polar) of dried leaves, bark, flowers and roots of Pongamia pinnata were prepared using Soxhlet apparatus. The extracts were screened for in vitro antimalarial activity against P. falciparum 3D7 strain. The cytotoxicity studies of crude extracts were conducted against Brine shrimp larvae and THP-1 cell line. Phytochemical analysis of the plant extracts was carried out by following the standard methods. The chemical injury to erythrocytes due to the plant extracts was checked. The in vivo study was conducted on P. berghei (ANKA) infected BALB/c albino mice by following 4-Day Suppressive, Repository, and Curative tests. Out of all the tested extracts, the methanol extract of the bark of Pongamia pinnata had shown an IC50 value of 11.67 μg/mL with potent in vitro antimalarial activity and cytotoxicity evaluation revealed that this extract was not toxic against Brine shrimp and THP-1 cells. The injury to erythrocytes analysis had not shown any morphological alterations and damage to the erythrocytes after 48 h of incubation. Because methanolic bark extract of Pongamia pinnata has shown good antimalarial activity in vitro, it was also tested in vivo. So the extract had exhibited an excellent activity against P. berghei malaria parasite while decrement of parasite counts was moderately low and dose-dependent (P < 0.05) when compared to the control groups, which shown a daily increase of parasitemia, unlike the CQ-treated groups. The highest concentration of the extract (1000 mg/kg b.wt./day) had shown 83.90, 87.47 and 94.67% of chemo-suppression during Suppressive, Repository, and Curative tests respectively which is almost nearer to the standard drug Chloroquine (5 mg/kg b.wt./day). Thus, the study has revealed that the methanolic bark extract had shown promisingly high ((P < 0.05) and dose-dependent chemo-suppression. The phytochemical screening of the crude extracts had shown the presence of alkaloids, flavonoids, triterpenes, tannins, carbohydrates, phenols, coumarins, saponins, phlobatannins and steroids. The present study is useful to develop new antimalarial drugs in the scenario of the growing resistance to the existing antimalarials. Thus, additional research is needed to characterize the bioactive molecules of the extracts of Pongamia pinnata that are responsible for inhibition of malaria parasite.

Synthesis of New Triazolopyrazine Antimalarial Compounds.

A radical approach to late-stage functionalization using photoredox and Diversinate™ chemistry on the Open Source Malaria (OSM) triazolopyrazine scaffold (Series 4) resulted in the synthesis of 12 new analogues, which were characterized by NMR, UV, and MS data analysis. The structures of four triazolopyrazines were confirmed by X-ray crystal structure analysis. Several minor and unexpected side products were generated during these studies, including two resulting from a possible disproportionation reaction. All compounds were tested for their ability to inhibit the growth of the malaria parasite Plasmodium falciparum (3D7 and Dd2 strains) and for cytotoxicity against a human embryonic kidney (HEK293) cell line. Moderate antimalarial activity was observed for some of the compounds, with IC50 values ranging from 0.3 to >20 µM; none of the compounds displayed any toxicity against HEK293 at 80 µM.

Two new bisindole alkaloids from Tabernaemontana macrocarpa Jack.

Two new bisindole alkaloids, bisnaecarpamines A (1) and B (2), possessing a vobasine-sarpagine type skeleton were isolated from the bark of Tabernaemontana macrocarpa Jack. Their structures were elucidated by extensive spectroscopic methods and chemical correlation. The absolute configurations of compounds 1 and 2 were established using TDDFT-ECD calculation of the selected isomers. Bisnaecarpamine A exhibited potent antimalarial activity against Plasmodium falciparum 3D7 strain with IC50 value of 28.8 µM.Graphic abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s11418-021-01510-4.

Assessing Anti-malaria Effect of Naja Naja Oxiana Snake Venom by Real-time Polymerase Chain Reaction Method

Objective: Malaria is one of the most important parasitic diseases and one of the important health issues especially in tropical and subtropical countries. The importance of this disease is due to its high prevalence and mortality, as well as drug resistance and side effects of common drugs used for its treatment. Snake venom is a complex mixture of active pharmaceutical ingredients. The present study aims to investigate the anti-Plasmodium falciparum activity of the purified fractions isolated from the venom of Iranian cobra snake (Naja Naja Oxiana) by real-time Polymerase Chain Reaction (PCR) method. The importance of this disease is due to its high prevalence, significant mortality, as well as drug resistance and, side effects of current drugs in treatment. Venom is a complex mixture of active pharmaceutical ingredients. The purpose of this study was to investigate the anti-Plasmodium falciparum activity of the purified fraction of Iranian cobra snake venom by Real -time PCR. Methods: After preparation and purification of lyophilized venom for determining the parasitic load, different fractions obtained from the venom of Naja Naja Oxiana put in different plates adjacent to Plasmodium falciparum (3D7) strain in the ring stage. The degree of parasitemia was determined by real-time PCR. Finally, the effective fraction with anti-malaria properties was identified. Results: The active fraction with a half maximal inhibitory concentration of 0.026 μg/mL was the most effective fraction on Plasmodium falciparum in vitro (P&lt;0.001). Conclusion: The active fraction of Naja Naja Oxiana venom at the mentioned concentration has anti-malaria effect. This results can motivate the continuation of further research in this field.

Isolation and identification of carotenoid-producing yeast and evaluation of antimalarial activity of the extracted carotenoid(s) against P. falciparum.

Plasmodial resistance to a variety of plant-based antimalarial drugs has led toward the discovery of more effective antimalarial compounds having chemical or biological origin. Since natural compounds are considered as safer drugs, in this study, yeast strains were identified and compared for the production of carotenoids that are well-known antioxidants and this metabolite was tested for its antiparasitic activity. Plasmodium falciparum 3D7 strain was selected as the target parasite for evaluation of antimalarial activity of yeast carotenoids using in vitro studies. Data were analyzed by FACS (fluorescence-activated cell sorter) and counted via gold standard Giemsa-stained smears. The extracted yeast carotenoids showed a profound inhibitory effect at a concentration of 10-3µg/µl and 10-4µg/µl when compared to β- carotene as control. SYBR Green1 fluorescent dye was used to confirm the decrease in parasitaemia at given range of concentration. Egress assay results suggested that treated parasite remained stalled at schizont stage with constricted morphology and were darkly stained. Non-toxicity of carotenoids on erythrocytes and on human liver hepatocellular carcinoma cells (HepG2 cells) was shown at a given concentration. This report provides strong evidence for antimalarial effects of extracted yeast carotenoids, which can be produced via a sustainable and cost-effective strategy and may be scaled up for industrial application.

Synthesis, Molecular Docking, and Evaluation of Some New Curcumin Analogs as Antimalarial Agents

This research involves the synthesis, antimalarial evaluation, and molecular docking of several curcumin analogs. A total of six curcumin analog compounds were synthesized using aldol condensation using hydrochloric acid and sodium hydroxide catalysts. The synthesized compounds were elucidated using FTIR, 1H-NMR, 13C-NMR, and LC-MS/MS. Subsequently, all curcumin analogs were tested as an antimalarial agent against Plasmodium falciparum 3D7 strain, and their mechanism of action was evaluated through a molecular docking study. Six curcumin analogs, i.e. 2,6-bis(2-hydroxybenzylidene)cyclohexanone; 2,6-bis(2-hydroxybenzylidene)cyclopentanone; 1.5-bis(2-hydroxyphenyl)penta-1,4-diene-3-one; 2,6-bis(3-hydroxybenzylidene)cyclo-hexanone; 2,6-bis(3-hydroxybenzylidene)cyclopentanone; and 1,5-bis(3-hydroxy-phenyl)penta-1,4-diene-3-one have been successfully synthesized. In addition, 2,6-bis(2-hydroxybenzylidene) cyclopentanone demonstrated the lowest IC50 value and binding affinity of 0.04 µM and -7.6 kcal/mol, respectively. Based on molecular docking studies, this compound also showed the most potent antimalarial activity targeted at PfATP6.

Plasmodium falciparum LipB mutants display altered redox and carbon metabolism in asexual stages and cannot complete sporogony in Anopheles mosquitoes

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.

Antiplasmodial Activity and Phytochemical Constituents of Selected Antimalarial Plants Used by Native People in West Timor Indonesia.

To document traditional antimalarial plants used by Tetun ethnic people in West Timor Indonesia and evaluate the antiplasmodial activity and phytochemicals of several plants that are widely used as oral medicine. A field study to document antimalarial plants followed by laboratory works to test antiplasmodial activity and identify the phytochemical constituents of some selected plants extract were applied. The inhibitory potency of ethanolic extracts of Strychnos ligustrina wood, roots of Calotropis gigantea, Fatuoa pilosa, and Neoalsomitra podagrica, whole plant of Cleome rutidosperma and Physalis angulata, stem barks of Alstonia spectabilis, Alstonia scholaris, Jatropha curcas and Plumeria alba, and leaves of Melia azedarach on the Plasmodium falciparum 3D7 strain in vitro were tested. Gas chromatography-mass spectrometry instrument was used to analyze the phytochemicals of the extracts. The Tetun ethnic people use 50 plant species as antimalarials. P. angulata, J. curcas, and A. spectabilis extracts show strong antiplasmodial activity with IC50 values of 0.22, 0.22, and 1.23 μg/mL, respectively; N. podagrica, A. scholaris, F. pilosa, and P. alba were moderate antiplasmodials with IC50 values of 11.60, 15.46, 24.92, and 36.39 μg/mL, respectively; and C. rutidosperma, M. azedarach, S. ligustrina, and C. gigantea were weak antiplasmodials with IC50 values of 54.25, 63.52, 63.91, and 66.49 μg/mL, respectively. The phytochemicals identification data indicate that these 11 plants contain alkaloids, terpenoids, steroids, coumarins, alcohols, thiols, phenolics, aldehydes, fatty acids, esters, and so forth. Plants widely used as antimalarials by the Tetun ethnic people is proven to have antiplasmodial activity.

An Integrative Computational Approach for the Prediction of Human-Plasmodium Protein-Protein Interactions.

Host-pathogen molecular cross-talks are critical in determining the pathophysiology of a specific infection. Most of these cross-talks are mediated via protein-protein interactions between the host and the pathogen (HP-PPI). Thus, it is essential to know how some pathogens interact with their hosts to understand the mechanism of infections. Malaria is a life-threatening disease caused by an obligate intracellular parasite belonging to the Plasmodium genus, of which P. falciparum is the most prevalent. Several previous studies predicted human-plasmodium protein-protein interactions using computational methods have demonstrated their utility, accuracy, and efficiency to identify the interacting partners and therefore complementing experimental efforts to characterize host-pathogen interaction networks. To predict potential putative HP-PPIs, we use an integrative computational approach based on the combination of multiple OMICS-based methods including human red blood cells (RBC) and Plasmodium falciparum 3D7 strain expressed proteins, domain-domain based PPI, similarity of gene ontology terms, structure similarity method homology identification, and machine learning prediction. Our results reported a set of 716 protein interactions involving 302 human proteins and 130 Plasmodium proteins. This work provides a list of potential human-Plasmodium interacting proteins. These findings will contribute to better understand the mechanisms underlying the molecular determinism of malaria disease and potentially to identify candidate pharmacological targets.

In silico study, synthesis, and evaluation of the antimalarial activity of hybrid dimethoxy pyrazole 1,3,5-triazine derivatives.

Malaria continues to become a major global health problem, particularly in Sub-Saharan Africa, Asia, and Latin America. The widespread emergence of resistance to first-line drugs has further bolstered an urgent need for a new and cost-effective antimalarial(s). Thus, the present study enumerates the synthesis of novel hybrid dimethoxy pyrazole 1,3,5-triazine derivatives7(a-j) and their in silico results short-listed three compounds with good binding energies and dock scores. Docking analysis shows that hydrogen-bonding predominates and typically involves key residues, such as Asp54, Tyr170, Ile164, and Arg122. The in vitro antimalarial evaluation of three top-ranked compounds (7e, 7g, and 7h) showed half-maximal inhibitory concentrationvalues range from 53.85 to 100 μg/ml against chloroquine-sensitive strain 3D7 of Plasmodium falciparum. Compound 7e may be utilized as a lead for further optimization work in drug discovery due to good antimalarial activity.

Heterologous Expression of the Biosynthetic Gene Cluster for Verticilactam and Identification of Analogues.

Verticilactam and the new geometric isomers, verticilactams B and C, were produced by heterologous expression of the biosynthetic gene cluster for verticilactam using the Streptomyces avermitilis SUKA17 strain. Only verticilactam, a compound with a characteristic β-ketoamide unit within a 16-membered polyketide macrolactam conjugated with an octalin skeleton, had been previously reported having been isolated from Streptomyces spiroverticillatus JC-8444. In this report, minor verticilactam derivatives were isolated from the transformed strain, and their structures elucidated by spectral analysis. Verticilactam B was a geometric isomer at Δ17 and Δ19, and verticilactam C was the Δ19 and Δ21 isomer. In addition, the absolute configuration of verticilactam was confirmed by ECD analysis and NMR chemical shifts. The stereochemistry assignments of the hydroxy groups at C-10 and C-12 were supported by the domain organization of the polyketide synthase identified in the verticilactam gene cluster. Verticilactam showed moderate activity against the malaria parasite Plasmodium falciparum 3D7 strain with no significant cytotoxicity or antimicrobial effects.

In Vitro Assessment of Antiplasmodial and Antitrypanosomal Activities of Chloroform, Ethyl Acetate and Ethanol Leaf Extracts of Oedera genistifolia

The high resistance evolution of protozoans to the existing antiparasitic drugs has necessitated the quest for novel and effective drugs against plasmodium and trypanosome parasites. As a result, this study aimed to assess the antiplasmodial and antitrypanosomal potentials of chloroform, ethyl acetate and ethanol leaf extracts of Oedera genistifolia. Standard biochemical procedures were explored for the plant extraction and gas chromatography-mass spectroscopy (GCMS) was used to identify the bioactive compounds in the crude extracts. The cytotoxic effects of the crude extracts were assessed against human cervix adenocarcinoma (HeLa cells) and their antiparasitic activities were investigated against Plasmodium falciparum strain 3D7 and Trypanosoma brucei brucei. GCMS analyses of the crude extracts revealed the bioactive compounds that could be responsible for the biological activities. The extracts had no cytotoxic effect on HeLa cells and demonstrated good antiplasmodial activity (chloroform extract: IC50 = 11.6 µg∙mL−1, ethyl acetate extract: IC50 = 3.3 µg∙mL−1 and ethanol extract: IC50 = 3.7 µg∙mL−1). Likewise, they showed excellent antitrypanosomal activity with IC50 = 0.5 µg∙mL−1 for chloroform and ethyl acetate extracts and IC50 = 0.4 µg∙mL−1 for the ethanol extract. Findings from the present study indicated that O. genistifolia could be a good source of strong antiplasmodial and antitrypanosomal agents.

Assessment of in vitro and in vivo antimalarial efficacy and GC-fingerprints of selected medicinal plant extracts

A hallmark of mortality and morbidity, malaria is affecting nearly half of the world's population. Emergence of drug-resistant strains of malarial parasite prompts identification and evaluation of medicinal plants and their constituents that may hold the key to a new and effective anti-malarial drug. In this context, nineteen methanolic extracts from seventeen medicinal plants were evaluated for anti-plasmodial potential against Plasmodium falciparum strain 3D7 (Chloroquine (CQ) sensitive) and INDO (CQ resistant) using fluorescence based SYBR-Green assay and for cytotoxic effects against mammalian cell lines. Leaf extract of two plants showed promising in vitro anti-malarial activity (Pf3D7 IC50 ≤ 10 μg/ml); one plant extract showed good activity (Pf3D7 IC50 = 10.1–20 μg/ml); seven were moderately active (IC50 = 20.1–50 μg/ml), four plant extracts showed poor activity (PfD7 IC50 = 50.1–100 μg/ml) and five extracts showed no activity up to IC50 = 100 μg/ml. Further, six extracts were found equipotent to PfINDO (resistance index ranging 0.4–2) and relatively nontoxic to mammalian cell lines HEK293 (cytotoxicity index ranging 1.4–12.5). Based on good resistance and selectivity indices, three extracts were evaluated for in vivo activity in Plasmodium berghei ANKA infected mice at a dose of 500 mg/kg and they showed significant suppression of P. berghei parasitemia. Further, these active plant extracts were fractionated using silica-gel chromatography and their fractions were evaluated for anti-plasmodial action. Obtained fractions showed enrichment in antimalarial activity. Active fractions were analyzed by gas chromatography and mass-spectrometery. Results suggests that the three active plant extracts could serve as potent source of anti-malarial agent and therefore require further analysis.

Discovery of 3-Cinnamamido-N-Substituted Benzamides as Potential Antimalarial Agents.

Malaria is one of the most devastating parasitic diseases, yet the discovery of antimalarial agents remains profoundly challenging. Very few new antimalarials have been developed in the past 50 years, while the emergence of drug-resistance continues to appear. This study focuses on the discovery, design, synthesis, and antimalarial evaluation of 3- cinnamamido-N-substituted benzamides. In this study, a screening of our compound library was carried out against the multidrugsensitive Plasmodium falciparum 3D7 strain. Derivatives of the hit were designed, synthesized and tested against P. falciparum 3D7 and the in vivo antimalarial activity of the most active compounds was evaluated using the method of Peters' 4-day suppressive test. The retrieved hit compound 1 containing a 3-cinnamamido-N-substituted benzamide skeleton showed moderate antimalarial activity (IC50 = 1.20 μM) for the first time. A series of derivatives were then synthesized through a simple four-step workflow, and half of them exhibited slightly better antimalarial effect than the precursor 1 during the subsequent in vitro assays. Additionally, compounds 11, 23, 30 and 31 displayed potent activity with IC50 values of approximately 0.1 μM, and weak cytotoxicity against mammalian cells. However, in vivo antimalarial activity is not effective, which might be ascribed to the poor solubility of these compounds. In this study, the phenotypic screen of our compound library resulted in the first report of a 3-cinnamamide framework with antimalarial activity and 40 derivatives were then designed and synthesized. Subsequent structure-activity studies showed that compounds 11, 23, 30 and 31 exhibited the most potent and selective activity against the P. falciparum 3D7 strain with IC50 values around 0.1 μM. Our work herein sets another example of phenotypic screen-based drug discovery, leading to potentially promising candidates of novel antimalarial agents once given further optimization.