Screening for antimalarial activity in the genus Potomorphe

Ethanolic extracts (CEE) of leaves from Potomorphe umbellata and Potomorphe peltata, popularly said to have antimalarial capacity, were submitted to the 4-day suppressive test in Plasmodium berghei-infected mice. The CEE of P. umbellata administered either orally (250 and 1250 mg/kg) or subcutaneously (100 and 500 mg/kg) evidenced strong antimalarial activity, significantly reducing the levels of parasitaemia in a dose-dependent manner. On the other hand, the CEE of P. peltata was ineffective in lowering the parasitemic levels in malarious mice, which had been treated either orally (500 mg/kg) or subcutaneously (20, 100 and 500 mg/kg). An ethanol extract of the dry whole plant of P. peltata was also inactive.     

Combination effects of chloroquine with the febrifugine and isofebrifugine mixture against a blood-induced infection with chloroquine-resistant Plasmodium berghei NK65 in ICR mice

The combination effects of chloroquine with a mixture of febrifugine and isofebrifugine were evaluated against a blood-induced infection with chloroquine-resistant P. berghei NK65 in ICR mice. Mice in the untreated control showed a progressively increasing parasitemia leading to mouse death. A two-day dosage of 20 mg base/kg of chloroquine alone showed little effect against P. berghei NK65 infection, and all mice died from day 13 to 14 with an increasing parasitemia. A four-day dosage of 1 mg/kg of the febrifugine and isofebrifugine mixture alone showed a little antimalarial activity, but all mice died from day 19 to 27 with an increasing parasitemia. On the other hand, mice treated with chloroquine plus alkaloids survived during the experiment. All mice treated with chloroquine alone or the alkaloid mixture alone showed low parasitemia levels during a drug administration and following a few days, but then malaria parasites increased in the bloodstream of the treated mice until death. On the other hand, malaria parasites in the mice given chloroquine plus alkaloids decreased on day 6 and then were not detected by a microscopic examination during observation period.     

Cassane- and norcassane-type diterpenes from Caesalpinia crista of Indonesia and their antimalarial activity against the growth of Plasmodium falciparum

The CH2Cl2 extract of the seed kernels of Caesalpinia crista, which exhibited promising antimalarial activity against Plasmodium berghei-infected mice in vivo, was examined and resulted in the isolation of seven new furanocassane-type diterpenes [caesalpinins C-G (1-5) and norcaesalpinins D and E (6, 7)] together with norcaesalpinins A-C (8-10) and 11 known compounds (norcaesalpinins A-C, 2-acetoxy-3-deacetoxycaesaldekarin e, caesalmin B, caesaldekarin e, caesalpin F, 14(17)-dehydrocaesalpin F, 2-acetoxycaesaldekarin e, 7-acetoxybonducellpin C, and caesalmin G). Their structures were determined on the basis of spectroscopic analysis. The isolated diterpenes showed significant dose-dependent inhibitory effects on Plasmodium falciparum FCR-3/A2 growth in vitro. Their IC50 values ranged from 90 nM to 6.5 microM, and norcaesalpinin E (7) showed the most potent inhibitory activity (IC50, 90 nM).     

Different responses of three rodent Plasmodia species,Plasmodium yoelii 17XL,P. berghei NK65 and P. chabaudi AS on treatment with febrifugine and isofebrifugine mixture from Hydrangea macrophylla var. Otaksa leaf in ICR mice

The antimalarial activity of Hydrangea macrophylla var. Otaksa alkaloids was evaluated against Plasmodium yoelii 17XL, P. berghei NK65 and P. chabaudi AS in ICR mice. For trials in P. yoelii 17XL or P. chabaudi AS infections, mice were infected intraperitoneally with 10(5), 10(6) and 10(7) parasitized erythrocytes, respectively, and in P. berghei NK65 infections, mice were infected intraperitoneally with 10(3), 10(4) and 10(5) parasitized erythrocytes, respectively. Three days after injection, mice were orally given febrifugine and isofebrifugine mixture at 1 mg/kg in the treated group and 0.5% cremophor EL solution in the untreated, infected one, respectively, twice a day for 5 consecutive days. In P. yoelii 17XL infections, mice in all the non-treated controls died from 5 to 9 dpi with a gradual body weight loss and increasing parasitemias. In the treated groups, the mouse body weight gradually decreased after the end of administration but turned to increase in several days, and except one mouse in the group given 10(6) parasitized erythrocytes, other mice survived during the experiment. Mice given orally the mixture showed low parasitemia levels during administration. Following a transient recrudescence of malaria parasites in the bloodstream of treated mice, no parasites could be detected by a microscopic examination. In P. berghei NK65 infections, mice in all the non-treated controls died from 7 to 12 dpi with a gradual body weight loss and increasing parasitemias. In the treated groups, the body weight gradually decreased from 11 dpi and all mice died from 12 to 30 dpi. During a mixture administration all mice showed slight suppression of multiplication of malaria parasites. After the end of administration, however, malaria parasites increased in the bloodstream of the treated mice and all mice died. In P. chabaudi AS infections, there were two different patterns in the course of infection; lethal infection or recovery in both the non-treated control and treated groups. In the non-treated and treated groups, mice showed a gradual body weight loss. But the body weights of survivals in both groups turned to increase in several days. Mice in control and treated groups showed as the same profile in the changes of parasitemia. In the non-treated controls, after a transient peak parasitemia malaria parasites in the bloodstream of survivals could not be detected by a microscopic examination. During a mixture administration, all mice showed suppression of multiplication of malaria parasites. After the end of medication, some mice died with increasing parasitemia. After a transient recrudescence, however, malaria parasites in the bloodstream of survivals could not be detected by a microscopic examination.     

New Orally Active Artemisinin Dimer Antimalarials

Objective: To synthesize orally bioavailable artemisinin dimers and the evaluation of their in vivo antimalarial activity. Methods: Artemsisin dimers were synthesized and their antimalarial activity was determined in in vitro and in vivo studies(administered orally and IP). Results: Dimers5 and 6 provided 100% suppression of parastemia throughout the oral administration study, with all animals surviving up to day 28(the last day of the study). Conclusion: Dimers 4-7 displayed markedly improved in vitro activity against P. falciparum, while the in vivo activity against P. berghei was highly encouraging, with 5 and 6 completely clearing parasitemia from the start of the drug treatment until the end of the study(day 28).     

Combination of artemisinin‐based natural compounds from Artemisia annua L. for the treatment of malaria: Pharmacodynamic and pharmacokinetic studies

Currently, the most effective antimalarial is artemisinin, which is extracted from the leaves of medicinal herb Artemisia annua L. (A. annua). Previous studies showed that the complex chemical matrix of A. annua could enhance both the bioavailability and efficacy of artemisinin. The present study aims to evaluate the efficacy and pharmacokinetic properties of a combination therapy based on artemisinin and 3 components from A. annua with high content (arteannuin B, arteannuic acid, and scopoletin). In vivo antimalarial activity was assessed following a 4‐day treatment in murine malaria models (Plasmodium yoelii and Plasmodium berghei). Results showed that a much sharper reduction in parasitemia (~93%) was found in combination therapy compared with pure artemisinin (~31%), indicating pharmacodynamic synergism occurring between artemisinin and arteannuin B, arteannuic acid, and scopoletin. Multiple‐dose pharmacokinetics further demonstrated that combination therapy results in increased area under the curve (AUC_0→∞), C_max, and t_1/2 by 3.78‐, 3.47‐, and 1.13‐fold in healthy mice, respectively, and by 2.62‐, 1.82‐, and 1.22‐fold in P. yoelii‐infected mice, respectively. The calculated oral clearance of combination therapy in healthy and P. yoelii‐infected mice was also reduced. These findings imply that specific components in A. annua might offer a possibility to develop new artemisinin‐based natural combination therapy for malaria treatment.     

In vivo antimalarial activity and toxicological effects of methanolic extract of Cocos nucifera (Dwarf red variety) husk fibre

OBJECTIVE: Phytochemical constituents as well as antimalarial and toxicity potentials of the methanolic extract of the husk fi bre of Dwarf Red variety of Cocos nucifera were evaluated in this study.METHODS: The dried powdered husk fi bre was exhaustively extracted with hexane, ethyl acetate and methanol successively and the methanolic extract was screened for fl avonoids, phenolics, tannins, alkaloids, steroids, triterpenes, phlobatannins, anthraquinones and glycosides. A 4-day suppressive antimalarial test was carried out using Plasmodium berghei NK65-infected mice, to which the extract was administered at doses of 31.25, 62.5, 125, 250 and 500 mg/kg body weight(BW). Toxicity of the extract was evaluated in rats using selected hematological parameters and organ function indices after orally administering doses of 25, 50 and 100 mg/kg BW for 14 d.RESULTS: Phytochemical analysis revealed the presence of alkaloids, tannins, phenolics, saponins, glycosides, steroids and anthraquinones in the extract. Moreover, the extract reduced parasitemia by 39.2% and 45.8% at doses of 250 and 500 mg/kg BW respectively on day 8 post-inoculation. Various hematological parameters evaluated were not significantly altered(P0.05) at all doses of the extract, except red blood cell count which was signifi cantly elevated(P0.05) at 100 mg/kg BW. The extract significantly increased(P0.05) urea, creatinine, cholesterol, high-density lipoprotein-cholesterol and bilirubin concentrations in the serum as well as atherogenic index, while it reduced albumin concentration significantly(P0.05) at higher doses compared to the controls. Alanine aminotransferase activity was reduced in the liver and heart signifi cantly(P0.05) but was increased in the serum signifi cantly(P0.05) at higher doses of the extract compared to the controls.CONCLUSION: The results suggest that methanolic extract of the Dwarf red variety has partial antimalarial activity at higher doses, but is capable of impairing normal kidney and liver function as well as predisposing subjects to cardiovascular diseases.     

Comparison of antimalarial activity of the alkaloidal fraction of Hydrangea macrophylla var. Otaksa leaves with the hot-water extract in ICR mice infected with Plasmodium yoelii 17 XL

The antimalarial activity of the fractions isolated from the leaves of Hydrangea macrophylla Seringe var. Otaksa Makino was evaluated against Plasmodium yoelii 17 XL in mice. Four different fractions were prepared in the usual manner to obtain an alkaloid fraction. All mice treated with the fraction containing febrifugine and isofebrifugine mixture at 1 mg/kg twice a day for 5 consecutive days survived during the experiment, and the change of mean parasitemia level showed almost the same pattern as that from mice treated with the hot-water extract of the same plant leaves. Activity of this fraction, however, was markedly reduced compared with the hot-water extract. Furthermore, no antimalarial activity was shown in the hotwater extract from H. macrophylla var. Otaksa roots or Dichroa febrifuga Lour. leaves.     

小柴胡汤及其与青蒿素配伍用药的抗疟作用研究

在伯氏鼠疟原虫感染的小鼠体内试验中研究了小柴胡汤及其与青蒿素配伍的抗疟作用，单用小柴胡汤醇提取物的抗疟作用甚微，当它和青蒿素联合用药时，二药并无疟增效作用，而且对伯氏鼠疟的复燃也无影响。     

Antimalarial activity of Bidens pilosa L. (Asteraceae) ethanol extracts from wild plants collected in various localities or plants cultivated in humus soil

Bidens pilosa (Asteraceae), a medicinal plant used worldwide, has antimalarial activity as shown in previous work. This study tested ethanol extracts from wild plants collected in three different regions of Brazil and from plants cultivated in various soil conditions. The extracts were active in mice infected with P. berghei: doses of < or =500 mg/kg administered by oral route reduced malaria parasitaemia and mouse mortality; higher doses were found to be less effective. Tested in vitro against three P. falciparum isolates, two chloroquine resistant and one mefloquine resistant, the plants cultivated under standard conditions, and in humus enriched soil, were active; but the wild plants were the most active. Analysis using thin layer chromatography demonstrated the presence of flavonoids (compounds considered responsible for the antimalarial activity) in all plants tested, even though at different profiles. Because B. pilosa is proven to be active against P. falciparum drug-resistant parasites in vitro, and in rodent malaria in vivo, it is a good candidate for pre-clinical tests as a phytotherapeutic agent or for chemical isolation of the active compounds with the aim of finding new antimalarial drugs.     

Antimalarial activity of some plants traditionally used in Meru district of Kenya

Ten plant extracts commonly used by the Meru community of Kenya were evaluated for the in vitro antiplasmodial, in vivo antimalarial, cytotoxicity and animal toxicity activities. The water and methanol extracts of Ludwigia erecta and the methanol extracts of Fuerstia africana and Schkuhria pinnata exhibited high antiplasmodial activity (IC(50) < 5 microg/mL) against chloroquine sensitive (D6) and resistant (W2) Plasmodium falciparum clones. The cytotoxicity of these highly active extracts on Vero E6 cells were in the range 161.5-4650.0 microg/mL with a selectivity index (SI) of 124.2-3530.7. In vivo studies of these extracts showed less activity with chemosuppression of parasitaemia in Plasmodium berghei infected mice of 49.64-65.28%. The methanol extract of Clerodendrum eriophyllum with a lower in vitro activity (IC(50) 9.51-10.56 microg/mL) exhibited the highest chemosuppression of 90.13%. The methanol and water extracts of Pittosporum viridiflorum were toxic to mice but at a lower dose prolonged survival of P. berghei infected mice (p < 0.05) with no overt signs of toxicity. However, the extracts were cytotoxic (SI, 0.96-2.51) on Vero E6 cells. These results suggest that there is potential to isolate active non-toxic antimalarial principles from these plants.     

Antimalarial compounds from Kniphofia foliosa roots

During the course of screening Ethiopian medicinal plants for their antimalarial properties, it was found that the dichloromethane extract of the roots of Kniphofia foliosa Hochst. (Asphodelaceae), which have long been used in the traditional medicine of Ethiopia for the treatment of abdominal cramps and wound healing, displayed strong in vitro antiplasmodial activity against the chloroquine-sensitive 3D7 strain of Plasmodium falciparum with an ED50 value of 3.8 microg/mL and weak cytotoxic activity against KB cells with an ED50 value of 35.2 microg/mL. Five compounds were isolated from the roots and evaluated for their in vitro antimalarial activity. Among the compounds tested, 10-(chrysophanol-7'-yl)-10-(xi)-hydroxychrysopanol-9-anthrone and chryslandicin, showed a high inhibition of the growth of the malaria parasite, P. falciparum with ED50 values of 0.260 and 0.537 microg/mL, respectively, while the naphthalene derivative, 2-acetyl-1-hydroxy-8-methoxy-3-methylnaphthalene, exhibited a less significant antimalarial activity with an ED50 value of 15.4 microg/mL. To compare the effect on the parasite with toxicity to mammalian cells, the cytotoxic activities of the isolated compounds against the KB cell line were evaluated and 10-(chrysophanol-7'-yl)-10-(xi)-hydroxychrysopanol-9-anthrone and chryslandicin displayed very low toxicity with ED50 values of 104 and 90 microg/mL, respectively. This is the first report of the inhibition of the growth of P. falciparum by anthraquinone-anthrone dimers and establishes them as a new class of potential antimalarial compounds with very little host cell toxicity.     

In vitro and in vivo antimalarial activity of cryptolepine,a plant-derived indoloquinoline

Cryptolepine is an indoloquinoline, high yields of which may be extracted from the roots of the West African shrub Cryptolepis sanguinolenta. The use of this plant as a traditional treatment for malaria is widespread in Ghana and is reported to be clinically effective. We have tested cryptolepine for in vitro antiplasmodial activity against the multidrug resistant (K1) strain of Plasmodium falciparum and found it to be highly active with an IC₅₀ value of 0.031±0.0085 (SE) μg/mL, equivalent to 0.134±0.037 μM (n = 3). In a 4-day suppression test there was, however, no significant reduction in parasitaemia in P. berghei-infected mice treated subcutaneously with cryptolepine (7–113 mg/kg/d×4), when compared with untreated controls. Like 9-aminoacridine, this compound appears to intercalate with DNA and this may explain the high degree of antimalarial activity demonstrated in vitro.     

Screening of medicinal plants from Reunion Island for antimalarial and cytotoxic activity

AIM OF THE STUDY: Nine plants from Reunion Island, selected using ethnopharmacology and chemotaxonomy, were investigated for their potential antimalarial value. MATERIALS AND METHODS: Thirty-eight extracts were prepared by maceration using CH(2)Cl(2) and MeOH, and were tested for in vitro activity against the 3D7 and W2 strain of Plasmodium falciparum. The most active extracts were then tested for in vitro cytotoxicity on human WI-38 fibroblasts to determine the selectivity index. Those extracts were also investigated in vivo against Plasmodium berghei infected mice. RESULTS: Most active of the extracts tested were the dichloromethane leaves extracts of Nuxia verticillata Lam. (Buddlejaceae), Psiadia arguta Voigt. (Asteraceae), Lantana camara L. (Verbenaceae), the methanol extracts from Aphloia theiformis (Vahl) Benn. (Aphloiaceae) bark, and Terminalia bentzoe L. (Combretaceae) leaves displaying in vitro IC(50) values ranging from 5.7 to 14.1mug/ml. Extracts from Psiadia, Aphloia at 200mg/(kgday) and Teminalia at 50mg/(kgday) also exhibited significant (p<0.0005) parasite inhibition in mice: 75.5%, 65.6% and 83.5%, respectively. CONCLUSION: Two plants showed interesting antimalarial activity with good selectivity: Aphloia theiformis and Terminalia bentzoe. Nuxia verticillata still needs to be tested in vivo, with a new batch of plant material.     

In vivo antimalarial activities of Quassia amara and Quassia undulata plant extracts in mice

Extracts obtained from two Nigerian Simaroubaceae plants, Quassia amara L. and Quassia undulata (Giull and Perr) D. Dietr were screened for antimalarial properties using a total of six extracts. The plant extracts showed significant antimalarial activities in the 4 day suppressive in vivo antimalarial assay in mice inoculated with red blood cells parasitized with Plasmodium berghei berghei. Plant extracts were studied at 100 mg and 200 mg per kg body weight mouse per day, respectively. At a concentration of 100 mg/kg of mouse, Q. amara leaf hexane extract had the highest suppressive activity with a parasite density of 0.16 +/- 0.001%. Q. amara leaf methanol extract had an outstanding activity; of 0.05 +/- 0.03% at 200 mg/kg. Chloroquine (10 mg/kg, positive control) had a suppressive activity of 0.34 +/- 0.02 in the same assay on day 4.     

Antimalarial agents, 4. Synthesis of a brusatol analog and biological activity of brusatol-related compounds

The quassinoids bruceoside-A [1], brusatol [2], and bruceolide [3] were tested for antimalarial activity in vitro against the chloroquine-resistant (Smith) isolates of Plasmodium falciparum. Compound 2 was quite active, 1 was not active, and 3 showed only a trace of activity. The fact that 15 [(E)-non-2-enoyl] bruceolide [7] synthesized from 2 was eight times less active than 2 would indicate that the requirement of a C-15 ester moiety for enhanced antimalarial activity among brusatol related quassinoids could be quite specific.     

Effects of Morinda lucida leaf extract on Trypanosoma brucei brucei infection in mice

The dried leaves of Morinda lucida were extracted with 50% methanol and the extract was recovered in a 9.7% w/w yield. Acute toxicity tests were performed in mice and the intraperitoneal LD₅₀ of the extract was 2000 . The extract induced purgation in mice from the first hour after oral administration and reached its peak between the third and fourth hour. The purgation was not dose-dependent. M. lucida leaf extract i.p. significantly suppressed the level of parasitemia after Trypanosoma brucei infection in mice. Suppression of existing parasitemia appeared dose-dependent with 1000 i.p. producing the maximum effect. The best trypanocidal activity was obtained when treatment with M. lucida extract commenced simultaneously with trypanosome inoculation.     

Antimalarial activity of methanolic extracts from plants used in Kenyan ethnomedicine and their interactions with chloroquine (CQ) against a CQ-tolerant rodent parasite, in mice

Methanolic extracts from 15 medicinal plants representing 11 families, used traditionally for malaria treatment in Kenya were screened for their in vivo antimalarial activity in mice against a chloroquine (CQ)-tolerant Plasmodium berghei NK65, either alone or in combination with CQ. The plant parts used ranged from leaves (L), stem bark (SB), root bark (RB), seeds (S) and whole plant (W). When used alone, extracts from seven plants, Clerodendrum myricoides (RB), Ficus sur (L/SB/RB), Maytenus acuminata (L/RB), Rhamnus prinoides (L/RB), Rhamnus staddo (RB), Toddalia asiatica (RB) and Vernonia lasiopus (RB) had statistically significant parasitaemia suppressions of 31.7-59.3%. In combination with CQ, methanolic extracts of Albizia gummifera (SB), Ficus sur (RB), Rhamnus prinoides and Rhamnus staddo (L/RB), Caesalpinia volkensii (L), Maytenus senegalensis (L/RB), Withania somnifera (RB), Ekebergia capensis (L/SB), Toddalia asiatica (L/RB) and Vernonia lasiopus (L/SB/RB) gave statistically significant and improved suppressions which ranged from 45.5 to 85.1%. The fact that these activities were up to five-fold higher than that of extract alone may suggest synergistic interactions. Remarkable parasitaemia suppression by the extracts, either alone or in combination with CQ mostly resulted into longer mouse survival relative to the controls, in some cases by a further 2 weeks. Plants, which showed significant antimalarial activity including Vernonia lasiopus, Toddalia asiatica, Ficus sur, Rhamnus prinoides and Rhamnus staddo warrant further evaluation in the search for novel antimalarial agents against drug-resistant malaria.     

Screening Azadirachta indica and Pisum sativum for possible antimalarial activities

Solvent-free extracts obtained from the leaves of Azadirachta indica and Pisum sativum were screened for antimalarial action using Plasmodium berghei in mice. Four days of oral dosing with 500 mg/kg and 125 mg/kg of the methanol extract of A. indica showed a parasite suppression which was statistically significant although all test animals died after 5 days, just 1 day longer than the untreated control group. A 50 mg/kg oral dose of the aqueous extract of P. sativum was found to have significant prophylactic activity by producing a parasite suppression of 31.9%.     

Schizontocidal activity of Celastrus paniculatus Willd. against Plasmodium falciparum in vitro

Preparations from the plant Celastrus paniculatus Willd. have been used for treatment of malaria and other febrile illness in the traditional medicine practices of Thailand. Crude solvent extracts from the root bark and stem of C. paniculatus were screened for antimalarial activity against P. falciparum using an in vitro culture system. A fraction of the chloroform extract of the root bark showed the highest antimalarial activity. An active principle was isolated and characterized from the chloroform fraction and identified as a quinonoid triterpene, pristimerin. When tested in vitro against various multidrug resistant isolates of P. falciparum, pristimerin was less active than the conventional antimalarial drugs tested.