Inhibition Of Parasite Growth Research Articles

Evaluation of antiplasmodial activity and inhibitions of lipid peroxidation and parasite haem polymerization activity by medicinal phytochemicals of Phyllanthus amarus

Despite the dedicated struggle to eliminate malaria, the current trend of the infection, particularly, in sub-Saharan Africa remains worrisome due to failing control and treatment approaches caused by a myriad of factors. Therefore, the search for new, affordable, and more potent antimalarial drugs, from plants especially, have become the frontline in recent times. This study thus, evaluates the in vitro antiplasmodial, cytotoxic and antioxidant activities of the phytochemical (alkaloids, flavonoids, tannins, saponins, cardiac glycosides and anthraquinones) extracts of Phyllanthus amarus using documented methods. Antiplasmodial and cytotoxic activities were determined by parasite growth inhibition assay and microassay technique by the lactate dehydrogenase method, respectively. Antioxidant activities were determined by measuring inhibition of both lipid peroxidation and heam polymerization by extracts. Results show that the alkaloid extract was noncytotoxic (CC = 60.26 μg/mL) and most selectable (SI = 125.5) with the highest antiplasmodial (IC = 0.48 μg/mL) and 50 50 haem polymerization inhibition (IC = 0.63 μg/mL) activities, but moderate antioxidant lipid peroxidation inhibition, (LPI; 50 IC = 500μg/mL) capacity. However, the ethanol and flavonoid phytochemical extracts displayed the highest antioxidant 50 activity in inhibition of heam polymerization (IC = 0.46 μg/mL) and lipid peroxidation (IC = 218.78 μg/mL), respectively, 50 50 with significant antiplasmodial activity (IC = 0.48 μg/mL and 1.10 μg/mL, respectively). Our results show that all 50s phytochemical extracts studied were non-cytotoxic. Although the antioxidant activities of the flavonoid and ethanol phytochemical extracts were greater in comparison to the alkaloid phytochemical, alkaloid was the most selectable active antiplasmodial phytochemical of P. amarus and one of its mechanisms of action is by inhibiting parasite haem detoxification.

Small molecule mediated inhibition of protein cargo recognition by peroxisomal transport receptor PEX5 is toxic to Trypanosoma

Trypanosomiases are life-threatening infections of humans and livestock, and novel effective therapeutic approaches are needed. Trypanosoma compartmentalize glycolysis into specialized organelles termed glycosomes. Most of the trypanosomal glycolytic enzymes harbor a peroxisomal targeting signal-1 (PTS1) which is recognized by the soluble receptor PEX5 to facilitate docking and translocation of the cargo into the glycosomal lumen. Given its pivotal role in the glycosomal protein import, the PEX5–PTS1 interaction represents a potential target to inhibit import of glycolytic enzymes and thus kill the parasite. We developed a fluorescence polarization (FP)-based assay for monitoring the PEX5–PTS1 interaction and performed a High Throughput Screening (HTS) campaign to identify small molecule inhibitors of the interaction. Six of the identified hits passed orthogonal selection criteria and were found to inhibit parasite growth in cell culture. Our results validate PEX5 as a target for small molecule inhibitors and provide scaffolds suitable for further pre-clinical development of novel trypanocidal compounds.

Effects of Structurally Different HDAC Inhibitors against Trypanosoma cruzi, Leishmania, and Schistosoma mansoni.

Neglected tropical diseases (NTDs), including trypanosomiasis, leishmaniasis, and schistosomiasis, result in a significant burden in terms of morbidity and mortality worldwide every year. Current antiparasitic drugs suffer from several limitations such as toxicity, no efficacy toward all of the forms of the parasites’ life cycle, and/or induction of resistance. Histone-modifying enzymes play a crucial role in parasite growth and survival; thus, the use of epigenetic drugs has been suggested as a strategy for the treatment of NTDs. We tested structurally different HDACi 1–9, chosen from our in-house library or newly synthesized, against Trypanosoma cruzi, Leishmania spp, and Schistosoma mansoni. Among them, 4 emerged as the most potent against all of the tested parasites, but it was too toxic against host cells, hampering further studies. The retinoic 2′-aminoanilide 8 was less potent than 4 in all parasitic assays, but as its toxicity is considerably lower, it could be the starting structure for further development. In T. cruzi, compound 3 exhibited a single-digit micromolar inhibition of parasite growth combined with moderate toxicity. In S. mansoni, 4’s close analogs 17–20 were tested in new transformed schistosomula (NTS) and adult worms displaying high death induction against both parasite forms. Among them, 17 and 19 exhibited very low toxicity in human retinal pigment epithelial (RPE) cells, thus being promising compounds for further optimization.

Isolation of a pentacyclic triterpenoid from the antiplasmodial bioactive fraction of Nauclea latifolia (Sm) roots

Purpose: To research the antiplasmodial property of aqueous extract, fractions, and residue of Nauclea latifolia roots and to isolate the components responsible for the antiplasmodial activity.Methods: Roots of N. latifolia were macerated with distilled water; the extract was obtained, successively partitioned with ethyl acetate and butanol. The extract, fractions, and the residue obtained were evaluated for their in vivo antiplasmodial activity and compared with amodiaquine and artesunate. The residue (which exhibited the best therapeutic index) was subjected to column and thin layer chromatography to isolate its components. Purification led to the isolation of betulinic acid, which was characterized with the aid of spectroscopic techniques (1H, 13C NMR, and EI-MS).Results: The residue significantly inhibited parasite growth from 42.8 % (D2) to 77.6 % (D5). Therefore, residue exhibited the highest therapeutic index against Plasmodium berghei in the three in vivo antiplasmodial (prophylactic, suppressive, and curative) models and it compared favourably with amodiaquine (80.5 %) and artesunate (85.9 %). The major component of the residue was betulinic acid.Conclusion: The results validate the antiplasmodial claims of the roots of N. latifolia in folkloric medicine, and demonstrated that the isolate has a high therapeutic index in this regard. Further investigations, however, are required to determine the clinical efficacy and safety of the compound/isolate.

New antimalarials identified by a cell-based phenotypic approach: Structure–activity relationships of 2,3,4,9-tetrahydro-1H-β-carboline derivatives possessing a 2-((coumarin-5-yl)oxy)alkanoyl moiety

The identification, structure–activity relationships (SARs), and biological effects of new antimalarials consisting of a 2,3,4,9-tetrahydro-1H-β-carboline core, a coumarin ring, and an oxyalkanoyl linker are described. A cell-based phenotypic approach was employed in this search for novel antimalarial drugs with unique modes of action. Our screening campaign of the RIKEN compound library succeeded in the identification of the known tetrahydro-β-carboline derivative (4e) as a hit compound showing significant in vitro activity. SAR studies on this chemical series led to the discovery of compound 4h having a (R)-methyl group on the oxyacetyl linker with potent inhibition of parasite growth (IC50 = 2.0 nM). Compound 4h was also found to exhibit significant in vivo antimalarial effects in mouse models. Furthermore, molecular modeling studies on 4e, 4h, and its diastereomer (4j) suggested that the (R)-methyl group of 4h forces the preferential adoption of a specific conformer which is considered to be an active conformer.

In Silico and In Vitro Antimalarial Screening and Validation Targeting Plasmodium falciparum Plasmepsin V.

Malaria chemotherapy is greatly threatened by the recent emergence and spread of resistance in the Plasmodium falciparum parasite against artemisinins and their partner drugs. Therefore, it is an urgent priority to develop new antimalarials. Plasmepsin V (PMV) is regarded as a superior drug target for its essential role in protein export. In this study, we performed virtual screening based on homology modeling of PMV structure, molecular docking and pharmacophore model analysis against a library with 1,535,478 compounds, which yielded 233 hits. Their antimalarial activities were assessed amongst four non-peptidomimetic compounds that demonstrated the promising inhibition of parasite growth, with mean IC50 values of 6.67 μM, 5.10 μM, 12.55 μM and 8.31 μM. No significant affection to the viability of L929 cells was detected in these candidates. These four compounds displayed strong binding activities with the PfPMV model through H-bond, hydrophobic, halogen bond or π-π interactions in molecular docking, with binding scores under −9.0 kcal/mol. The experimental validation of molecule-protein interaction identified the binding of four compounds with multiple plasmepsins; however, only compound 47 showed interaction with plasmepsin V, which exhibited the potential to be developed as an active PfPMV inhibitor.

In vivo antimalarial efficacy of Psidium guajava leaf crude extract and fractions in Plasmodium berghei infected mice

Background: Malaria is a life-threatening disease caused by the protozoan parasite, Plasmodium. The emergence of drug-resistant Plasmodium species to currently available antimalarials has necessitated the search for more effective drugs. This study evaluated the antimalarial potential of the crude extract and fractions of Psidium guajava leaf in Plasmodium berghei infected mice. Method: Mice infected with Plasmodium berghei (P. berghei) were administered orally with the crude extract and fractions at doses ranging from 100-500 and 50-200mg/kg/day respectively, for five consecutive days. Results: The crude extract significantly (p<0.05) inhibited parasite growth as well as prevented body weight loss and packed cell volume reduction dose-dependently. Among the fractions, aqueous fraction was the most active with 54.26% inhibition of parasite growth at 200mg/kg. Remarkable inhibition of parasite growth by the crude extract and aqueous fraction was evident in the prolongation of mice survival relative to the control (27.33±1.76, 24.67±0.67, 28.0±1.16 and 8.33±0.67 for crude extract (500mg/kg), aqueous fraction (200mg/kg), chloroquine and negative control groups respectively). Phytochemical screening of the crude extract revealed the presence of phenol, alkaloids, flavonoids, and terpenoids. Conclusion: The results indicate that crude extract and aqueous fraction of P. guajava leaf are potent antimalarial agent that can be employed in the development of antimalarial drugs.

A simple quinoline salt derivative is active in vitro against Plasmodiumfalciparum asexual blood stages and inhibits the development of cerebral malaria in murine model

Chloroquine (CQ) was the most effective and widely used drug for the prophylaxis and treatment of severe and non-severe malaria. Although its prophylactic use has led to resistance to P. falciparum in all endemic countries, CQ still remains the drug of choice for the treatment of vivax malaria. Otherwise, the speed in which parasite resistance to available antimalarials rises and spreads in endemic regions points to the urgent need for the development of new antimalarials. Quinoline derivatives have been used as a tool in the search for new drugs and were investigated in the present study in an attempt to produce a HIT compound to avoid the cerebral malarial (CM). Seven compounds were synthesized, including three quinoline derivate salts. The cytotoxicity and antiplasmodial activity were assayed in vitro, highlighting compound 3 as a HIT, which also showed interaction with ferriprotoporphyrin IX similarly to CQ. Physicochemical and pharmacokinetic properties of absorption were found to be favorable when analyzed in silico. The in vivo assays, using the experimental cerebral malaria (ECM) model, showed important values of parasite growth inhibition on the 7th day-post infection (Q15 15 mg/kg: 76.9%, Q30 30 mg/kg: 90,1% and Q50 50 mg/kg: 92,9%). Compound 3 also showed significant protection against the development of CM, besides hepatic and renal parameters better than CQ. In conclusion, this quinoline derivative demonstrated promising activity for the treatment of malaria and was able to avoid the development of severe malaria in mice.

Antimalarial Activity of Ethanol Extract of Kelakai Leaves (Stenochlaena palustris) to Parasitemia and Splenomegaly in BALB/c Mice Infected with Plasmodium berghei ANKA

Introduction: Malaria is one of global health problems. Splenomegaly is one of malaria symptoms. Antimalarial drug resistance had been reported. Alternative treatment is by using traditional medicinal plants such as kelakai (Stenochlaena palustris). Kelakai contains alkaloid and flavonoid which had been reported to have antimalarial activity. The aim of this study was to discover antimalarial activity of ethanol extract of kelakai leaves to parasitemia and splenomegaly of Plasmodium berghei ANKA in infected BALB/c mice.Methods: This study was based on a modified Peter test using BALB/c mice infected with P. berghei ANKA treated with ethanol extract of kelakai leaves, with chloroquine diphosphate as a positive control. The negative control was P. berghei ANKA infected mice without any additional treatment. Administration of ethanol extract of kelakai leaves was performed for 4 days with a serial doses of 100, 10, and 1 mg/kg body weight. The positive control was given chloroquine diphosphate 20 mg/kg body weight. Parasitemia was observed daily prior to the calculation of the percentage of parasite growth and parasite growth inhibition. At the end of the test, the mice were sacrificed and spleens were isolated to measure their sizes. Probit analysis was performed to obtain ED50 to find the effect of extract in parasite killing by 50%. Spearman test was performed to analyze the correlation of doses of extract and splenomegaly.Results: Parasitemia growth inhibition was directly proportional to the dose. Higher parasitemia inhibition was obtained at higher doses and vice versa. Result of probit analysis showed an ED50 was 77.05 mg/kg body weight. Statistical analysis resulted in insignificant correlation between doses and splenomegaly p = 1.0 (significancy < 0.05).Conclusion: Ethanol extract of kelakai leaves possessed good antimalarial activity and there was no correlation between extract doses and splenomegaly in Plasmodium berghei ANKA-infected mice.

In vitro antiprotozoal effect of alcoholic extract of hemolymph of Galleria mellonella larva against Trichomonas gallinae

Trichomonas gallinae is a protozoan parasite that lives in the upper gastrointestinal tract of birds. Recently, the hemolymph of Galleria mellonella has been widely used as an anti-parasitic drug. The present work aimed to investigate the inhibitory activity of an alcoholic extract of G. mellonella hemolymph (AEGmH) on T. gallinae in vitro compared with that of metronidazole using wet smear and vital stain acridine orange (AO). The results showed that the degree of growth inhibition of Trichomonas was based on the AEGmH concentration. Furthermore, the highest reduction of parasitic growth (100%) was observed in cultures treated with 25, 12.5, and 6.25mg/mL AEGmH before 24h. Moreover, the same results were detected in cultures treated with 3.1 and 1.6mg/mL AEGmH, but after 48h, and doses of AEGmH (0.8 and 0.4mg/mL) after 96h. In comparison, complete inhibition of parasite growth (100%) was obtained by metronidazole at 25mg/mL after 72h. Besides, light microscopy observations revealed changes in trophozoites' morphology in culture treated with AEGmH. We concluded that the alcoholic extract of hemolymph of G. mellonella is suitable to counter trichomoniasis in vitro and showed antiprotozoal potential.

Preparation, characterization, and evaluation of eosin B-loaded nano-liposomes for growth inhibition of Plasmodium falciparum.

Malaria is a deadly disease in humans caused by the Plasmodium parasite. High prevalence of malaria and resistance of malaria parasite to currently proposed drugs have increased the need to introduce and use new and effective antimalarial agents. In this study, eosin B was used as an effective antimalarial agent, the efficacy of which has already been confirmed by in vitro models. Also, for efficacy and safety improvement of eosin B, liposomal nanocarrier was used because of diversity and adaptability in controlled drug delivery and targeting. Eosin B was trapped inside liposomal nanocarriers by thin layer hydration method and its optimization was performed based on size, polydispersity index, and drug entrapment efficiency. Finally, the eosin B-loaded liposomes were tested on Plasmodium falciparum in culture to evaluate its anti-plasmodial effect. According to the results, the formulation with DSPC:cholesterol 8:1 (molar ratio) and drug concentration of 3 mg/ml was selected as the optimal form. The optimal nano-liposomes showed a size of 163.3 nm, a polydispersity index of 0.250, and an encapsulation efficiency of 69.94%. The process of drug release from nanocarriers was also obtained about 63% at the end of 72 h. Stability studies over 2 months at 25 °C and 4 °C on the optimum sample showed that the samples stored in the refrigerator were more stable in terms of size characteristics, polydispersity index, and drug entrapment efficiency. The results indicate a greater effect of liposomal-formulated eosin B on inhibiting parasite growth compared to the free eosin B.

Antiplasmodial Activity of Griffipavixanthone and Morelloflavone the Main Compounds from Garcinia Chromocarpa Engl. (Clusiaceae)

Ethnopharmacological relevance: The genus Garcinia is a rich source of species mostly used in traditional medicine to treat a many diseases. Bioactive constituents from this genus have been used as antimicrobial, anticancer, antimalarial, anti-inflammatory, hepatoprotective and anti-HIV. According to these properties, major compounds of this plant have been evaluated for their antiplasmodial activity. Materials and methods: The methanol extract of the G. chromocarpa stem bark was used in this study. The chromatographic fractionation of this latest led to the isolation of two major compounds, identified by NMR and MS spectroscopic techniques. The crude extract and pure compounds were compared using the in vitro evaluation of the malaria parasite growth inhibition by colorimetric method (p-LDH assay). Furthermore ABTS•+ and DPPH• scavenging activities and cytotoxicity through WST1 assay were evaluated. Results: Based on the chromatographic profile two major compounds were isolated. They were characterized by spectroscopic analysis interpretation and comparison with the data in the literature: one biflavonoid (1) and one xanthone (2). The compound 2 (Griffipavixanthone, IC50 ± S.D = 5.80±0.32 μg/mL) was found to be more active against the malaria parasite, chloroquinesensitive (3D7) strain of P. falciparum, than the compound 1 (Morelloflavone, IC50 ± S.D = 9.20±0.96 μg/mL). The antiradical activities connected to the ability to scavenge free radicals were observed for the ethanol crude extract of the stem bark, and the leave of G. chromocarpa. Conclusions: This work demonstrated for the first time the antiplasmodial activity of G. chromocarpa and its isolated major compounds. These latest are known in the genus Garcinia but, here, firstly described in G. chromocarpa Engl.

The Effect of Andrographis paniculata Nees on Oxidative Stress and Parasitemia Levels of Plasmodium berghei Infected Rats

Background: During malaria infection, oxidative stress arises due to the high metabolic rate of the multiplying parasite within the erythrocyte. Malondialdehyde (MDA), a product of lipid peroxidation and glutathione (GSH) has been suggested as a biomarker of oxidative stress. The Ethyl acetate (EA) fraction from the ethanol extract of Andrographis paniculata was shown to inhibit Plasmodium berghei in vivo. However, the antimalarial mechanism of the EA fraction, specifically on oxidative stress has not been investigated previously. Therefore, this study aimed to investigate the effects of the EA fraction on parasitemia levels, GSH and MDA levels of P. berghei infected rats. Methods: Female Wistar rats infected with P. berghei were divided into three groups. Group one received no treatment (negative control), group two was treated with 1.4 mg/200 g body weight of chloroquine diphosphate as positive control, and group three was treated with the EA fraction at a dose equal to andrographolide 3.5 mg/200 g body weight. The treatments lasted for four days (day 0 to day 3) and parasitemia was observed from day 0 to day 4. Rats were sacrificed and blood taken intracardially on day 4 after parasitemia observation. GSH was measured using an ELISA reader at a wavelength of 415 nm. MDA was observed via spectrophotometry at a wavelength of 532 nm. Results: The EA fraction at a dose equal to andrographolide 3.5 mg/200 g body weight was able to inhibit parasite growth by 81.97±9.14%. The GSH levels of the negative control, positive control and EA fraction treated group were 139.30±75.93 μMol/mL, 81.06±53.26 μMol/mL and 105.71±76.00 μMol/mL, respectively. Furthermore, the MDA level of negative control, positive control and EA fraction treated group were 11.18±0.70 nMol mL, 8.81±1.26 nMol/mL and 9.40±0.74 nMol/mL, respectively. No significant differences were detected between treatment groups regarding their GSH levels. Additionally, there was a significant difference in MDA levels between the negative control and positive control groups; as well as a significant difference between the negative control and the EA treated group. However, no significant difference in MDA levels between the EA fraction treated group and positive control group. Interestingly, a correlation was found between parasite growth inhibition and MDA levels among groups (p<0.05). Conclusion: The EA fraction of A. paniculata significantly decreased MDA levels which correlated significantly with parasitemia levels of P. berghei infected rats. The antimalarial activity of the EA fraction may have been correlated with oxidative stress mechanisms and this correlation could be explained in part by the decreased production of MDA.

Systematic Analysis of Clemastine, a Candidate Apicomplexan Parasite-Selective Tubulin-Targeting Agent.

Apicomplexan parasites, such as Toxoplasma gondii, Plasmodium spp., Babesia spp., and Cryptosporidium spp., cause significant morbidity and mortality. Existing treatments are problematic due to toxicity and the emergence of drug-resistant parasites. Because protozoan tubulin can be selectively disrupted by small molecules to inhibit parasite growth, we assembled an in vitro testing cascade to fully delineate effects of candidate tubulin-targeting drugs on Toxoplasma gondii and vertebrate host cells. Using this analysis, we evaluated clemastine, an antihistamine that has been previously shown to inhibit Plasmodium growth by competitively binding to the CCT/TRiC tubulin chaperone as a proof-of-concept. We concurrently analyzed astemizole, a distinct antihistamine that blocks heme detoxification in Plasmodium. Both drugs have EC50 values of ~2 µM and do not demonstrate cytotoxicity or vertebrate microtubule disruption at this concentration. Parasite subpellicular microtubules are shortened by treatment with either clemastine or astemizole but not after treatment with pyrimethamine, indicating that this effect is not a general response to antiparasitic drugs. Immunoblot quantification indicates that the total α-tubulin concentration of 0.02 pg/tachyzoite does not change with clemastine treatment. In conclusion, the testing cascade allows profiling of small-molecule effects on both parasite and vertebrate cell viability and microtubule integrity.

Repurposing the Trypanosomatidic GSK Kinetobox for the Inhibition of Parasitic Pteridine and Dihydrofolate Reductases.

Three open-source anti-kinetoplastid chemical boxes derived from a whole-cell phenotypic screening by GlaxoSmithKline (Tres Cantos Anti-Kinetoplastid Screening, TCAKS) were exploited for the discovery of a novel core structure inspiring new treatments of parasitic diseases targeting the trypansosmatidic pteridine reductase 1 (PTR1) and dihydrofolate reductase (DHFR) enzymes. In total, 592 compounds were tested through medium-throughput screening assays. A subset of 14 compounds successfully inhibited the enzyme activity in the low micromolar range of at least one of the enzymes from both Trypanosoma brucei and Lesihmania major parasites (pan-inhibitors), or from both PTR1 and DHFR-TS of the same parasite (dual inhibitors). Molecular docking studies of the protein–ligand interaction focused on new scaffolds not reproducing the well-known antifolate core clearly explaining the experimental data. TCMDC-143249, classified as a benzenesulfonamide derivative by the QikProp descriptor tool, showed selective inhibition of PTR1 and growth inhibition of the kinetoplastid parasites in the 5 μM range. In our work, we enlarged the biological profile of the GSK Kinetobox and identified new core structures inhibiting selectively PTR1, effective against the kinetoplastid infectious protozoans. In perspective, we foresee the development of selective PTR1 and DHFR inhibitors for studies of drug combinations.

In vitro growth inhibitory activity of Medicines for Malaria Venture pathogen box compounds against Leishmania aethiopica

IntroductionLeishmania aethiopica (L. aethiopica) is responsible for different forms of cutaneous leishmaniasis (CL) in Ethiopia. Treatment heavily depends on limited drugs, together with drawbacks like toxicity and microbial resistance. The current research aimed to investigate in vitro growth inhibitory activity of Medicines for Malaria Ventures - Pathogen Box (MMV - PB) compounds against L. aethiopica clinical isolate.MethodologyFour hundred MMV – PB compounds were screened against L. aethiopica using resazurin based colourimetric assay. Compounds with > 70% inhibition were further tested using macrophage based intracellular amastigote assay. Cytotoxic and hemolytic activity of candidate hits were assessed on THP1- cells and sheep red blood cells (RBCs), respectively. In vitro drug interaction study was also conducted for the most potent hit using the combination index method.ResultsAt the test concentration of 1 μM, twenty-three compounds showed > 50% inhibition of promastigotes parasite growth, of which 11 compounds showed > 70% inhibition. The 50% growth inhibition (IC50) of the 11 compounds was ranged from 0.024 to 0.483 μM in anti-promastigote assay and from 0.064 to 0.899 μM in intracellular amastigote assay. Candidate compounds demonstrated good safety on sheep RBCs and THP-1 cell lines. MMV688415 demonstrated a slight hemolytic activity on sheep RBC (5.3% at 25 μM) and THP-1 cell line (CC20 = 25 μM) while MMV690102 inhibited half of THP-1 cells at 36.5 μM (selectivity index = 478). No synergistic activity was observed from the combinations of MMV690102 and amphotericin B (CI > 1), and MMV690102 and Pentamidine (CI > 1) at lower and higher combination points.ConclusionThe present study identified a panel of compounds that can be used as a novel starting point for lead optimization. MMV690102 appears to be the most potent inhibitor against L. aethiopica promastigotes and amastigotes. Future works should investigate the antileishmanial mechanism of action and in vivo antileishmanial activities of identified hits.

Development of peptidomimetic hydroxamates as PfA-M1 and PfA-M17 dual inhibitors: Biological evaluation and structural characterization by cocrystallization

Plasmodium parasites causing malaria have developed resistance to most of the antimalarials in use, including the artemisinin-based combinations, which are the last line of defense against malaria. This necessitates the discovery of new targets and the development of novel antimalarials. Plasmodium falciparum alanyl aminopeptidase (PfA-M1) and leucyl aminopeptidase (PfA-M17) belong to the M1 and M17 family of metalloproteases respectively and play critical roles in the asexual erythrocytic stage of development. These enzymes have been suggested as potential antimalarial drug targets. Herein we describe the development of peptidomimetic hydroxamates as PfA-M1 and PfA-M17 dual inhibitors. Most of the compounds described in this study display inhibition at sub-micromolar range against the recombinant PfA-M1 and PfA-M17. More importantly, compound 26 not only exhibits potent malarial aminopeptidases inhibitory activities (PfA-M1 Ki = 0.11 ± 0.0002 µmol/L, PfA-M17 Ki = 0.05 ± 0.005 µmol/L), but also possesses remarkable selectivity over the mammalian counterpart (pAPN Ki = 17.24 ± 0.08 µmol/L), which endows 26 with strong inhibition of the malarial parasite growth and negligible cytotoxicity on human cell lines. Crystal structures of PfA-M1 at atomic resolution in complex with four different compounds including compound 26 establish the structural basis for their inhibitory activities. Notably, the terminal ureidobenzyl group of 26 explores the S2′ region where differences between the malarial and mammalian enzymes are apparent, which rationalizes the selectivity of 26. Together, our data provide important insights for the rational and structure-based design of selective and dual inhibitors of malarial aminopeptidases that will likely lead to novel chemotherapeutics for the treatment of malaria.

The anti-parasite action of imidazole derivatives likely involves oxidative stress but not HIF-1α signaling

BackgroundTherapeutic options for toxoplasmosis are limited. This fact underscores ongoing research efforts to identify and develop better therapy. Previously, we reported the anti-parasitic potential of a new series of derivatives of imidazole. ObjectiveIn the current investigation, we attempted the investigation of the possible action mechanism of few promising anti-parasite imidazole derivatives namely C1 (bis-imidazole), C2 (phenyl-substituted 1H-imidazole) and C3 (thiophene-imidazole) MethodsWe evaluated if oxidative stress, hypoxia as well as metabolic reprogramming of host l-tryptophan pathway form part of the parasite growth inhibition by imidazoles. Anti-parasite assay was performed for imidazoles at concentrations ranging from 0 to 10 μM, while pyrimethamine was used as reference drug to validate assay. ResultsImidazole compounds restricted parasite growth dose-dependently. However, in the presence of an antioxidant (Trolox), l-tryptophan and/or CoCl2 (chemical inducer of hypoxia), the growth inhibitory efficacy of imidazoles was appreciably abolished. Further, imidazole treatment led to elevated level of reactive oxygen species, while reducing parasite mitochondrial membrane potential compared with control. In contrast, imidazole had no effect on host HIF-1α level suggesting its exclusion in the anti-parasite action. ConclusionTaken together, imidazole-based compounds might restrict parasite growth by causing oxidative stress. The findings provide new insight on the likely biochemical mechanisms of imidazoles as prospective anti-parasite therapy. Data gives new perspective that not only underscores the anti-parasite prospects of imidazoles, but implicates the host l-tryptophan pathway as a feasible treatment option for T. gondii infections.

Antiplasmodial Activity of Griffipavixanthone and Morelloflavone the Main Compounds from Garcinia Chromocarpa Engl. (Clusiaceae)

Ethnopharmacological relevanceThe genus Garcinia is a rich source of species mostly used in traditional medicine to treat a many diseases. Bioactive constituents from this genus have been used as antimicrobial, anticancer, antimalarial, anti-inflammatory, hepatoprotective and anti-HIV. The methanol stem bark extract from Garcinia chromocarpa has been fractionated using preparative HPLC and column chromatography to identify major compounds of this plant and to evaluate their antiplasmodial activity.Aim of the studyThis study was aimed to report the antiplasmodial activity of Griffipavixanthone and Morelloflavone isolated for the first time from G. chromocarpa. And the absence of cytotoxicity at the highest tested dose (100 µg/mL) have been demonstrated. This aspect could justify their use in traditional medicine.Materials and methodsChromatographic fractionation of the stem bark methanol extract led to the isolation of major compounds, identified by NMR and MS spectroscopic techniques. The crude extract and pure compounds were used for the in vitro evaluation of the malaria parasite growth inhibition by colorimetric method (p-LDH assay), of the antiradical activities and of their cytotoxicity through WST1 assay.ResultsBased on the chromatographic profile two major compounds were isolated. They were characterized by spectroscopic analysis interpretation and comparison with the data in the literature: one biflavonoid (1) and one xanthone (2). The compound 2 (Griffipavixanthone, IC50 ± S.D = 5.80±0.32 μg/mL) was found to be more active against the malaria parasite, chloroquine-sensitive (3D7) strain of P. falciparum, than the compound 1 (Morelloflavone, IC50 ± S.D = 9.20±0.96 μg/mL). The antiradical activities connected to the ability to scavenge free radicals were determined for the ethanol crude extract of the stem bark, and the leave of G. chromocarpa.ConclusionsThis work demonstrated for the first time the antiplasmodial activity of G. chromocarpa and its isolated major compounds. These latest are known in the genus Garcinia but, here, firstly described in G. chromocarpa Engl.

Biflavones from Platonia insignis Mart. Flowers Promote In Vitro Antileishmanial and Immunomodulatory Effects against Internalized Amastigote Forms of Leishmania amazonensis.

Leishmaniasis is an infectious disease that affects millions of people worldwide, making the search essential for more accessible treatments. The species Platonia insignis Mart. (Clusiaceae) has been extensively studied and has gained prominence for its pharmacological potential. The objective of this work was to evaluate the antileishmania activity, cytotoxic effect and activation patterns of macrophages of hydroalcoholic extract (EHPi), ethyl acetate fractions (FAcOEt) and morelloflavone/volkensiflavone mixture (MB) from P. insignis flowers. EHPi, FAcOEt and MB demonstrated concentration-dependent antileishmania activity, with inhibition of parasite growth in all analyzed concentrations. EHPi exhibited maximum effect at 800 μg/mL, while FAcOEt and MB reduced the growth of the parasite by 94.62% at 800 μg/mL. EHPi, FAcOEt and MB showed low cytotoxic effects for macrophages at 81.78, 159.67 and 134.28 μg/mL, respectively. EHPi (11.25 µg/mL), FAcOEt (11.25 and 22.5 µg/mL) and MB (22.5 µg/mL) characterized the increase in lysosomal activity, suggesting a possible modulating effect. These findings open for the application of flowers from a P. insignis flowers and biflavones mixture thereof in the promising treatment of leishmaniasis.