Akedanones A-C, In Vitro and In Vivo Antiplasmodial 2,3-Dihydronaphthoquinones Produced by Streptomyces sp. K20-0187.

Three new antiplasmodial compounds, named akedanones A (1), B (2), and C (3), were discovered from the cultured material of Streptomyces sp. K20-0187 isolated from a soil sample collected at Takeda, Kofu, Yamanashi prefecture in Japan. The structures of compounds 1-3 were elucidated as new 2,3-dihydronaphthoquinones having prenyl and reverse prenyl groups by mass spectrometry and nuclear magnetic resonance analyses. Compound 1 and the known furanonaphthoquinone I (4) showed potent in vitro antiplasmodial activity against chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum strains, with half-maximal inhibitory concentration values ranging from 0.06 to 0.3 µM. Compounds 1 and 4 also displayed potent in vivo antiplasmodial activity against drug-sensitive rodent malaria Plasmodium berghei N strain, with inhibition rates of 47.6 and 43.1%, respectively, on intraperitoneal administration at a dose of 5 mg kg-1 day-1 for 4 days.

Xylopic acid-amodiaquine and xylopic acid-artesunate combinations are effective in managing malaria in Plasmodium berghei-infected mice.

BACKGROUND: Evidence of Plasmodium resistance to some of the current anti-malarial agents makes it imperative to search for newer and effective drugs to combat malaria. Therefore, this study evaluated whether the co-administrations of xylopic acid-amodiaquine and xylopic acid-artesunate combinations will produce a synergistic anti-malarial effect. METHODS: Antiplasmodial effect of xylopic acid (XA: 3, 10, 30, 100, 150 mg kg-1), artesunate (ART: 1, 2, 4, 8, 16 mg kg-1), and amodiaquine (AQ: 1.25, 2.5, 5, 10, 20 mg kg-1) were evaluated in Plasmodium berghei (strain ANKA)-infected mice to determine respective ED50s. Artemether/lumefantrine was used as the positive control. XA/ART and XA/AQ were subsequently administered in a fixed-dose combination of their ED50s (1:1) and the combination fractions of their ED50s (1/2, 1/4, 1/8, 1/16, and 1/32) to determine the experimental ED50s (Zexp). An isobologram was constructed to determine the nature of the interaction between XA/ART, and XA/AQ combinations by comparing Zexp with the theoretical ED50 (Zadd). Bodyweight and 30-day survival post-treatment were additionally recorded. RESULTS: ED50s for XA, ART, and AQ were 9.0 ± 3.2, 1.61 ± 0.6, and 3.1 ± 0.8 mg kg-1, respectively. The Zadd, Zexp, and interaction index for XA/ART co-administration was 5.3 ± 2.61, 1.98 ± 0.25, and 0.37, respectively while that of XA/AQ were 6.05 ± 2.0, 1.69 ± 0.42, and 0.28, respectively. The Zexp for both combination therapies lay significantly (p < 0.001) below the additive isoboles showing XA acts synergistically with both ART and AQ in clearing the parasites. High doses of XA/ART combination significantly (p < 0.05) increased the survival days of infected mice with a mean hazard ratio of 0.40 while all the XA/AQ combination doses showed a significant (p < 0.05) increase in the survival days of infected mice with a mean hazard ratio of 0.27 similar to AL. Both XA/ART and XA/AQ combined treatments significantly (p < 0.05) reduced weight loss. CONCLUSION: Xylopic acid co-administration with either artesunate or amodiaquine produces a synergistic anti-plasmodial effect in mice infected with P. berghei.

In vivo anti-malarial activity of the hydroalcoholic extract of rhizomes of Kniphofia foliosa and its constituents.

BACKGROUND: Kniphofia foliosa is a flamboyant robust perennial herb which has dense clumps and tick upright rhizomes with leaves at the base. In Ethiopia, it has several vernacular names including Abelbila, Ashenda, Amelmela, Yeznjero Ageda, Shemetmetie and Yezinjero Ageda. The plant is endemic to Ethiopian highlands, where its rhizomes are traditionally used for the treatment of malaria, abdominal cramps and wound healing. In the present study, the 80% methanol extract of K. foliosa rhizomes and its constituents are tested against Plasmodium berghei in mice. METHODS: Isolation was carried out using column and preparative thin layer chromatography (PTLC). The chemical structures of the compounds were elucidated by spectroscopic methods (ESI-MS, 1D and 2D-NMR). Peters' 4-day suppressive test against P. berghei in mice was utilized for in vivo anti-malarial evaluation of the test substances. RESULTS: Two compounds, namely knipholone and dianellin were isolated from the 80% methanolic extract of K. foliosa rhizomes, and characterized. The hydroalcoholic extract (400 mg/kg) and knipholone (200 mg/kg) showed the highest activity with chemosuppression values of 61.52 and 60.16%, respectively. From the dose-response plot, the median effective (ED50) doses of knipholone and dianellin were determined to be 81.25 and 92.31 mg/kg, respectively. Molecular docking study revealed that knipholone had a strong binding affinity to Plasmodium falciparum l-lactate dehydrogenase (pfLDH) target. CONCLUSION: Results of the current study support the traditional use of the plant for the treatment of malaria.

Preclinical evaluation of strasseriolides A-D, potent antiplasmodial macrolides isolated from Strasseria geniculata CF-247,251.

BACKGROUND: Malaria is a global health problem for which novel therapeutic compounds are needed. To this end, a recently published novel family of antiplasmodial macrolides, strasseriolides A-D, was herein subjected to in vivo efficacy studies and preclinical evaluation in order to identify the most promising candidate(s) for further development. METHODS: Preclinical evaluation of strasseriolides A-D was performed by MTT-based cytotoxicity assay in THLE-2 (CRL-2706) liver cells, cardiotoxicity screening using the FluxOR™ potassium assay in hERG expressed HEK cells, LC-MS-based analysis of drug-drug interaction involving CYP3A4, CYP2D6 and CYP2C9 isoforms inhibition and metabolic stability assays in human liver microsomes. Mice in vivo toxicity studies were also accomplished by i.v. administration of the compounds (vehicle: 0.5% HPMC, 0.5% Tween 80, 0.5% Benzyl alcohol) in mice at 25 mg/kg dosage. Plasma were prepared from mice blood samples obtained at different time points (over a 24-h period), and analysed by LC-MS to quantify compounds. The most promising compounds, strasseriolides C and D, were subjected to a preliminary in vivo efficacy study in which transgenic GFP-luciferase expressing Plasmodium berghei strain ANKA-infected Swiss Webster female mice (n = 4-5) were treated 48 h post-infection with an i.p. dosage of strasseriolide C at 50 mg/kg and strasseriolide D at 22 mg/kg for four days after which luciferase activity was quantified on day 5 in an IVIS® Lumina II imager. RESULTS: Strasseriolides A-D showed no cytotoxicity, no carditoxicity and no drug-drug interaction problems in vitro with varying intrinsic clearance (CLint). Only strasseriolide B was highly toxic to mice in vivo (even at 1 mg/kg i.v. dosage) and, therefore, discontinued in further in vivo studies. Strasseriolide D showed statistically significant activity in vivo giving rise to lower parasitaemia levels (70% lower) compared to the controls treated with vehicle. CONCLUSIONS: Animal efficacy and preclinical evaluation of the recently discovered potent antiplasmodial macrolides, strasseriolides A-D, led to the identification of strasseriolide D as the most promising compound for further development. Future studies dealing on structure optimization, formulation and establishment of optimal in vivo dosage explorations of this novel compound class could enhance their clinical potency and allow for progress to later stages of the developmental pipeline.

A novel multiple-stage antimalarial agent that inhibits protein synthesis.

There is an urgent need for new drugs to treat malaria, with broad therapeutic potential and novel modes of action, to widen the scope of treatment and to overcome emerging drug resistance. Here we describe the discovery of DDD107498, a compound with a potent and novel spectrum of antimalarial activity against multiple life-cycle stages of the Plasmodium parasite, with good pharmacokinetic properties and an acceptable safety profile. DDD107498 demonstrates potential to address a variety of clinical needs, including single-dose treatment, transmission blocking and chemoprotection. DDD107498 was developed from a screening programme against blood-stage malaria parasites; its molecular target has been identified as translation elongation factor 2 (eEF2), which is responsible for the GTP-dependent translocation of the ribosome along messenger RNA, and is essential for protein synthesis. This discovery of eEF2 as a viable antimalarial drug target opens up new possibilities for drug discovery.

Phytol suppresses parasitemia and ameliorates anaemia and oxidative brain damage in mice infected with Plasmodium berghei.

The quest for the development of a novel antimalarial drug informed the decision to subject phytol to in vivo trials following a demonstration of therapeutic potential against chloroquine sensitive strain of Plasmodium falciparum under in vitro condition. On this basis, the in vivo anti-Plasmodium berghei activity of phytol including the ameliorative effects of the compound on P. berghei-associated anaemia and organ damage were investigated. Mice were infected with chloroquine-sensitive strain of P. berghei and were treated with phytol at a dose of 10 and 20 mg/kg body weight (BW) for four days. The levels of parasitemia, packed cell volume and redox sensitive biomarkers of liver, brain and spleen tissues were determined. Our result revealed that phytol significantly (p < 0.05) suppressed the multiplication of P. berghei in a dose-dependent manner. Additionally, the phytol significantly (p < 0.05) ameliorated the P. berghei-induced anaemia and brain damage. Data from the present study demonstrated that phytol has suppressive effect on P. berghei and could ameliorate some P. berghei-induced pathological changes.

Rocaglates as dual-targeting agents for experimental cerebral malaria.

Cerebral malaria (CM) is a severe and rapidly progressing complication of infection by Plasmodium parasites that is associated with high rates of mortality and morbidity. Treatment options are currently few, and intervention with artemisinin (Art) has limited efficacy, a problem that is compounded by the emergence of resistance to Art in Plasmodium parasites. Rocaglates are a class of natural products derived from plants of the Aglaia genus that have been shown to interfere with eukaryotic initiation factor 4A (eIF4A), ultimately blocking initiation of protein synthesis. Here, we show that the rocaglate CR-1-31B perturbs association of Plasmodium falciparum eIF4A (PfeIF4A) with RNA. CR-1-31B shows potent prophylactic and therapeutic antiplasmodial activity in vivo in mouse models of infection with Plasmodium berghei (CM) and Plasmodium chabaudi (blood-stage malaria), and can also block replication of different clinical isolates of P. falciparum in human erythrocytes infected ex vivo, including drug-resistant P. falciparum isolates. In vivo, a single dosing of CR-1-31B in P. berghei-infected animals is sufficient to provide protection against lethality. CR-1-31B is shown to dampen expression of the early proinflammatory response in myeloid cells in vitro and dampens the inflammatory response in vivo in P. berghei-infected mice. The dual activity of CR-1-31B as an antiplasmodial and as an inhibitor of the inflammatory response in myeloid cells should prove extremely valuable for therapeutic intervention in human cases of CM.

Transmission-blocking compound candidates against Plasmodium vivax using P. berghei as an initial screening.

BACKGROUND: Different strategies for improvement of malaria control and elimination are based on the blockage of malaria parasite transmission to the mosquito vector. These strategies include the drugs that target the plasmodial sexual stages in humans and the early developmental stages inside mosquitoes. OBJECTIVES: Here we tested Malaria Box compounds in order to evaluate their activity against male and female gametocytes in Plasmodium berghei, mosquito infection in P. vivax and ookinete formation in both species. METHODS/FINDINGS: The membrane feeding assay and the development of ookinetes by a 24 h ex vivo culture and the ookinete yield per 1000 erythrocytes were used to test transmission-blocking potential of the Malaria Box compounds in P. vivax. For P. berghei we used flow cytometry to evaluate male and female gametocyte time course and fluorescence microscopy to check the ookinete development. The two species used in this study showed similar results concerning the compounds' activity against gametocytes and ookinetes, which were different from those in P. falciparum. In addition, from the eight Malaria Box compounds tested in both species, compounds MMV665830, MMV665878 and MMV665941 were selected as a hit compounds due the high inhibition observed. CONCLUSION: Our results showed that P. berghei is suitable as an initial screening system to test compounds against P. vivax.

Chemotherapeutic and prophylactic antimalarial drugs induce cell death through mitochondrial-mediated apoptosis in murine models.

Malaria is a parasitic disease that has defied many treatment plans. This study was carried out to investigate the host mitochondrial response to malarial infection and selected antimalarial chemotherapy using murine models. The effects of artesunate (ART) and proguanil (PRG) on mitochondrial Permeability Transition (mPT), mitochondrial ATPase (mATPase), level of malondialdehyde (MDA) and activities of antioxidant enzymes; catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), Xanthine oxidase (XO), glutathione S-transferase (GST) and reduced glutathione (GSH) were estimated in Plasmodium berghei-infected mice treated with ART and PRG. Besides, apoptotic markers, such as caspases 3, 9 and DNA fragmentation were estimated. Unparasitised (NORMAL) and parasitized but untreated (PU) animals were used as controls. The mPT pore opening fold of 9 (ART), 3 (PRG), and 4 (PU) were observed relative to calcium (23) for in vivo study. In vitro, graded concentrations (20, 40, 80 and 160 µg/mL) of ART gave mPT induction folds of 1, 21, 23 and 25, respectively, relative to calcium (9) while PRG did not have effect in the absence of calcium. In vivo, ART significantly (p < 0.001) enhanced mATPase activity than PRG. The PRG and ART increased the MDA levels in vivo. Oral administration of ART and PRG altered antioxidant enzymes status, Caspases 3 and 9 were significantly activated in PRG-treated groups; there was significant increase in DNA fragmentation in PU and PRG groups compared with the normal control. The results obtained showed that malaria parasite and antimalarial drugs cause mitochondrial-mediated apoptosis.

In Vivo Antimalarial Activity of Leaf Extracts and a Major Compound Isolated from Ranunculus multifidus Forsk.

The leaves of Ranunculus multifidus Forsk. are traditionally used for the treatment of malaria in several African countries. In the present study, 80% methanol (RM-M) and hydrodistilled (RM-H) extracts of fresh leaves from R. multifidus and its major constituent anemonin were tested for their in vivo antimalarial activity against Plasmodium berghei in mice. Anemonin was also tested for its in vitro antimycobacterial activity against Mycobacterium smegmatis and M. abscessus in a microbroth dilution assay, and bacterial growth was analyzed by OD measurement. The isolation of anemonin from RM-H was carried out using preparative thin layer chromatography (PTLC). The chemical structures of anemonin and its hydrolysis product were elucidated using spectroscopic methods (HR-MS; 1D and 2D-NMR). Results of the study revealed that both RM-M and RM-H were active against P. berghei in mice, although the latter demonstrated superior activity (p < 0.001), as compared to the former. At a dose of 35.00 mg/kg/day, RM-H demonstrated a chemosuppression value of 70% in a 4-day suppressive test. In a 4-day suppressive, Rane's and prophylactic antimalarial tests, anemonin showed median effective doses (ED50s) of 2.17, 2.78 and 2.70 µM, respectively. However, anemonin did not inhibit the growth of M. smegmatis and M. abscessus.

Regulated rutin co-administration reverses mitochondrial-mediated apoptosis in Plasmodium berghei-infected mice.

Malarial infection causes apoptosis in hepatocytes. However, it is not known if co-administration of antimalarial drug with rutin will reverse the apoptotic effects of malarial infection. Plasmodium berghei-infected mice were assigned into groups as follows: groups I to III were treated with the vehicle (Parasitised Untreated, PU), 10 mg/kg body weight of Artesunate-Mefloquine (AM) and Dihydroartemisinin-Piperaquine (DP) respectively. Groups IV to VII were treated with AM, DP but co-administered with 100, 200 mg rutin/kg body weight while groups VIII and IX received rutin (100 and 200 mg/kg body weight). Liver mitochondrial Permeability Transition (mPT) and ATPase (mATPase) were determined spectrophotometrically. Caspases 3 and 9 were assayed using ELISA while the levels of bax, cytochrome c release (CCR), p53 and bcl-2 expressions were assayed immunohistochemically. The mPT pore opening fold of 5 (PU), 16 (AM), 14 (AM + 100 mg rutin/kg body weight), 9 (AM + 200 mg rutin/kg body weight), 4(DP), were observed relative to calcium (24) while DP, rutin and their combinations did not open the pore. AM and DP significantly increased caspases 3 and 9 activities, enhanced mATPase activity but co-treatment with rutin (100 mg/kg) decreased these effects significantly. AM + rutin (100 mg/kg body weight) significantly decreased bax, p53, CCR and increased bcl-2 expression. The results showed that supplementing malarial treatment with rutin decreased apoptosis suggesting that rutin supplementation can minimise apoptosis in malarial infection.

Nanotized curcumin-benzothiophene conjugate: A potential combination for treatment of cerebral malaria.

The declining effectiveness of the available antimalarial drugs due to drug resistance requires a continued effort to develop new therapeutic approaches. In this context, combination therapies hold a great promise for developing effective first-line antimalarial treatments for reducing malaria mortality. The present study explores the antimalarial efficacy of nanotized formulation of curcumin in combination with benzothiophene compound 6 (3-bromo-N-(4-fluorobenzyl)-benzo[b]thiophene-2-carboxamide) with a view to achieve better efficacy at a very low dose in comparison to that accomplished with monotherapy alone. Herein, we formulated nanotized conjugate of curcumin and compound 6 (cur-compound 6) in the size range of 30-90 nm as observed via TEM, AFM and DLS analysis in the study. The nanotized preparation was found to be readily dispersible in water, physically and chemically stable and exhibited sustained release profile of both curcumin and compound 6 till 48 hr. Treatment of P. falciparum parasites with the nanotized conjugate for 24 hr resulted in rapid clearance of the parasites. Furthermore, P. berghei infected mice treated with nanotized conjugate formulation survived till 90 days with complete eradication of the parasites from RBC. This improved efficacy of the nanotized formulation was possible because of the increased absorption of the compounds via oral administration owing to enhanced dispersibility of the formulation in aqueous medium. Moreover, an improved oral bioavailability of the nanotized formulation lowered the dosage at which the pharmacological effect was achieved while avoiding any observable adverse harmful side effects.

Evaluation of in vivo anti-malarial potential of omidun obtained from fermented maize in Ibadan, Nigeria.

BACKGROUND: The menace of resistance to anti-malarial drugs is a great challenge to malaria control, necessitating the search for new anti-malarial agents. This search has led to the exploration of natural products for efficacy in malaria therapy. Omidun is the supernatant of fermenting maize (ogi) slurry that has been widely investigated and reported to possess several health benefits and it is used traditionally as solvent for preparing anti-malarial herbs. However, there is no information on the anti-malarial activity of omidun itself. This study was conducted to investigate the prophylactic, curative and suppressive anti-malarial potential of omidun. METHODS: Experimental mice in the curative group were infected with 1 × 106 cells of Plasmodium berghei strain ANKA and treated with either 0.2 ml of omidun containing 3 × 109 cfu/ml of viable lactic acid bacteria or 0.2 ml of 5 mg/kg of chloroquine (positive control) or 0.2 ml of saline (negative control) for 4 days from day 3 post infection. The prophylactic group of mice were pre-treated with either omidun, chloroquine or saline for 4 days before infection with P. berghei, while the suppressive group was treated with omidun or chloroquine or saline and infected with P. berghei simultaneously. A group of mice were uninfected but treated (with omidun and control samples), while a final group was uninfected and untreated (controls). Parasitaemia and histopathology analysis were done in all groups. RESULTS: The curative and suppressive groups showed a significant difference between the omidun-treated mice (100% parasitaemia reduction) and the untreated mice (54.5% parasitaemia increase). There was no significance difference between the omidun treatment and chloroquine (positive control) treatment in suppressive group as both treatment had 100% parasitaemia reduction. The omidun prophylactic treatment however did not show any parasitaemia suppression, but a significant difference was observed between the omidun treatment (85% increase) and the chloroquine (positive control) treatment (100% reduction) in the group. Omidun treatment is non-toxic to the kidney. CONCLUSION: This study provides scientific evidence supporting omidun usage in the treatment of malaria. Consequently, further work may yield the specific component of omidun responsible for the anti-malarial activity.

In silico and in vivo anti-malarial investigation on 1-(heteroaryl)-2-((5-nitroheteroaryl)methylene) hydrazine derivatives.

BACKGROUND: Resistance of Plasmodium falciparum against common anti-malarial drugs emphasizes the need of alternative and more effective drugs. Synthetic derivatives of 1-(heteroaryl)-2-((5-nitroheteroaryl)methylene) hydrazine have showed in vitro anti-plasmodial activities. The present study aimed to evaluate the molecular binding and anti-plasmodial activity of synthetic compounds in vivo. METHODS: The molecular docking was used to study the binding of compounds to haem and Plasmodium falciparum lactate dehydrogenase (PfLDH). Acute toxicity of the synthetic compounds was evaluated based on the modified up & down method. The anti-plasmodial activity of the compounds was conducted by the two standard tests of Peters' and of Rane, using chloroquine-sensitive Plasmodium berghei in mice. Also, the toxicity to the internal organs of mice was evaluated on the seventh day after the treatment in addition to the histopathology of their liver. Compound 3 that showed high activity in the lowest dose was selected for further pharmacodynamic studies. RESULTS: According to the docking studies, the active site of PfLDH had at least four common residues, including Ala98, Ile54, Gly29, and Tyr97 to bind the compounds with the affinity, ranging from - 8.0 to - 8.4 kcal/mol. The binding mode of ligands to haem revealed an effective binding affinity, ranging from - 5.1 to - 5.5 kcal/mol. Compound 2 showed the highest  % suppression of parasitaemia (99.09%) at the dose of 125 mg/kg/day in Peters' test. Compound 3, with 79.42% suppression, was the best in Rane's test at the lowest dose (31 mg/kg/day). Compound 3 was confirmed by the pharmacodynamic study to have faster initial parasite elimination in the lowest concentration. The histopathology of the livers of mice did not reveal any focal necrosis of hepatocytes in the studied compounds. CONCLUSIONS: The docking studies verified Pf LDH inhibition and the inhibitory effect on the haemozoin formation for the studied compounds. Accordingly, some compounds may provide new avenues for the development of anti-malarial drugs without liver toxicity, although further studies are required to optimize their anti-plasmodial activity.

Half-Sandwich Cyclopentadienylruthenium(II) Complexes: A New Antimalarial Chemotype.

A small library of "half-sandwich" cyclopentadienylruthenium(II) compounds of the general formula [(η5-C5R5)Ru(PPh3)(N-N)][PF6], a scaffold hitherto absent from the toolbox of antiplasmodials, was screened for activity against the blood stage of CQ-sensitive 3D7-GFP, CQ-resistant Dd2, and artemisinin-resistant IPC5202 Plasmodium falciparum strains and the liver stage of Plasmodium berghei. The best-performing compounds displayed dual-stage activity, with single-digit nanomolar IC50 values against blood-stage malaria parasites, nanomolar activity against liver-stage parasites, and residual cytotoxicity against HepG2 and Huh7 mammalian cells. The parasitic absorption/distribution of 7-nitrobenzoxadiazole-appended fluorescent compounds Ru4 and Ru5 was investigated by confocal fluorescence microscopy, revealing parasite-selective absorption in infected erythrocytes and nuclear accumulation of both compounds. The lead compound Ru2 impaired asexual parasite differentiation, exhibiting fast parasiticidal activity against both ring and trophozoite stages of a synchronized culture of the P. falciparum 3D7 strain. These results point to cyclopentadienylruthenium(II) complexes as a highly promising chemotype for the development of dual-stage antiplasmodials.

A Meroisoprenoid, Heptenolides, and C-Benzylated Flavonoids from Sphaerocoryne gracilis ssp. gracilis.

A new meroisoprenoid (1), two heptenolides (2 and 3), two C-benzylated flavonoids (4 and 5), and 11 known compounds (6-16) were isolated from leaf, stem bark, and root bark extracts of Sphaerocoryne gracilis ssp. gracilis by chromatographic separation. The structures of the new metabolites 1-5 were established by NMR, IR, and UV spectroscopic and mass spectrometric data analysis. (Z)-Sphaerodiol (7), (Z)-acetylmelodorinol (8), 7-hydroxy-6-hydromelodienone (10), and dichamanetin (15) inhibited the proliferation of Plasmodium falciparum (3D7, Dd2) with IC50 values of 1.4-10.5 µM, although these compounds also showed cytotoxicity against human embryonic kidney HEK-293 cells. None of the compounds exhibited significant disruption in protein translation when assayed in vitro.

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.

Structure-Activity Relationship of Anti-malarial Allylpyrocatechol Isolated from Piper betle.

Malaria disease remains a serious worldwide health problem. In South-East Asia, one of the malaria infection "hot-spots," medicinal plants such as Piper betle have traditionally been used for the treatment of malaria, and allylpyrocatechol (1), a constituent of P. betle, has been shown to exhibit anti-malarial activities. In this study, we verified that 1 showed in vivo anti-malarial activity through not only intraperitoneal (i.p.) but also peroral (p.o.) administration. Additionally, some analogs of 1 were synthesized and the structure-activity relationship was analyzed to disclose the crucial sub-structures for the potent activity.

Comparison of the antimalarial activity of a Colombian traditional Uitoto remedy with laboratory preparations.

BACKGROUND & OBJECTIVES: In Colombian Amazonia, Uitoto indigenous people use a preparation of Curarea toxicofera (Menispermaceae) to prevent and treat malaria. To open the way for the production of a standardized herbal remedy, we compared the activity of the traditional preparation with laboratory preparations. METHODS: People were interviewed on their mode of use and preparation of what is considered the best remedy against fevers in this area. The herbal remedy was prepared according to the healer's recommendations. The plant was also submitted to continuous distillation and percolation extraction. The preparations were then tested against Plasmodium falciparum, in vitro. Traditional preparation and extract obtained by percolation were tested on Plasmodium berghei infected mice. Chemical profiles were also explored by thin-layer chromatography. RESULTS: Yields of extraction were around 7% in the preparations (percolation was the most efficient). The phytochemical profile showed a mix of steroids, flavonoids and alkaloids qualitatively similar in all preparations. In vitro, the extracts showed inhibitory concentration 50 <10µg/mL: the traditional preparation was almost three times less active than laboratory preparations. In vivo, percolation was also more active than traditional preparation, inhibiting 78% of the parasite growth at 400mg/kg/day by oral route. INTERPRETATION & CONCLUSION: Pharmacological activities suggest that both the original remedy (prepared according to traditional pharmacopeia) and the extracts obtained by percolation extraction exhibit relevant antiparasitic activity. C. toxicofera should therefore be considered for the elaboration of an improved traditional medicine by implementing toxicological studies and carefully following quality control guidelines for its preparation.

Novel Harmicines with Improved Potency against Plasmodium.

Harmicines represent hybrid compounds composed of ß-carboline alkaloid harmine and cinnamic acid derivatives (CADs). In this paper we report the synthesis of amide-type harmicines and the evaluation of their biological activity. N-harmicines 5a-f and O-harmicines 6a-h were prepared by a straightforward synthetic procedure, from harmine-based amines and CADs using standard coupling conditions, 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo [4,5-b]pyridinium 3-oxid hexafluorophosphate (HATU) and N,N-diisopropylethylamine (DIEA). Amide-type harmicines exerted remarkable activity against the erythrocytic stage of P. falciparum, in low submicromolar concentrations, which was significantly more pronounced compared to their antiplasmodial activity against the hepatic stages of P. berghei. Furthermore, a cytotoxicity assay against the human liver hepatocellular carcinoma cell line (HepG2) revealed favorable selectivity indices of the most active harmicines. Molecular dynamics simulations demonstrated the binding of ligands within the ATP binding site of PfHsp90, while the calculated binding free energies confirmed higher activity of N-harmicines 5 over their O-substituted analogues 6. Amino acids predominantly affecting the binding were identified, which provided guidelines for the further derivatization of the harmine framework towards more efficient agents.