Plants as a source of antimalarial drugs

Toxicological assessment of the hydroethanolic leaf extract of clerodendrum capitatum in Wistar rats

Introduction

Clerodendrum capitatum (Willd) Schumach. & Thonn (Lamiaceae) is used in African traditional medicine for the treatment of malaria, hypertension, obesity, jaundice and diabetes however there is lack of experimental data on its possible toxicity. This study investigated the acute and 28 days sub-chronic toxicity of C. capitatum in Wistar rats.

Methods

In acute toxicity tests, a single administration of the hydroethanolic C. capitatum leaf extract (5 g/kg) was given orally to 5 female rats. The general behavior, adverse effects and mortality were recorded for up to 14 days post treatment. On the 15^th day, the rats were weighed and euthanized for necropsy. In sub-chronic toxicity tests, the extract (4, 8 and 16 g/kg/day) was given orally to both male and female rats for 28 days. The animal body weight was recorded throughout the experiment, while hematological and biochemical parameters of blood and relative organs weights were evaluated on the 29^th day.

Results

Clerodendrum Capitatum did not cause any death or any hazardous symptoms of acute toxicity, showing an LD₅₀ higher than 5 g/kg. Sub-chronic administration of C. capitatum resulted in no noticeable changes in weight gain and water or food consumption. White blood cells and hemoglobin increased while urea concentration, liver enzymes, total cholesterol and glucose concentrations significantly decreased in treated animals. No changes in macroscopical aspect of organs were observed in the animals.

Conclusion

These results showed that acute or sub-chronic oral administration of the hydroethanolic leaf extract of Clerodendrum capitatum may be considered as relatively free of toxicity.

An ethnobotanical study of anti-malarial plants among indigenous people on the upper Negro River in the Brazilian Amazon

BACKGROUND

In this article we present the plants used for the treatment of malaria and associated symptoms in Santa Isabel do Rio Negro in the Brazilian Amazon. The region has important biological and cultural diversities including more than twenty indigenous ethnic groups and a strong history in traditional medicine.

OBJECTIVE

The aims of this study are to survey information in the Baniwa, Baré, Desana, Piratapuia, Tariana, Tukano, Tuyuca and Yanomami ethnic communities and among caboclos (mixed-ethnicity) on (a) plant species used for the treatment of malaria and associated symptoms, (b) dosage forms and (c) distribution of these anti-malarial plants in the Amazon.

METHODS

Information was obtained through classical ethnobotanical and ethnopharmacological methods from interviews with 146 informants in Santa Isabel municipality on the upper Negro River, Brazil.

RESULTS

Fifty-five mainly native neotropical plant species from 34 families were in use. The detailed uses of these plants were documented. The result was 187 records (64.5%) of plants for the specific treatment of malaria, 51 records (17.6%) of plants used in the treatment of liver problems and 29 records (10.0%) of plants used in the control of fevers associated with malaria. Other uses described were blood fortification ('dar sangue'), headache and prophylaxis. Most of the therapeutic preparations were decoctions and infusions based on stem bark, root bark and leaves. These were administered by mouth. In some cases, remedies were prepared with up to three different plant species. Also, plants were used together with other ingredients such as insects, mammals, gunpowder and milk.

CONCLUSION

This is the first study on the anti-malarial plants from this region of the Amazon. Aspidosperma spp. and Ampelozizyphus amazonicus Ducke were the most cited species in the communities surveyed. These species have experimental proof supporting their anti-malarial efficacy. The dosage of the therapeutic preparations depends on the kind of plant, quantity of plant material available, the patient's age (children and adults) and the local expert. The treatment time varies from a single dose to up to several weeks. Most anti-malarial plants are domesticated or grow spontaneously. They are grown in home gardens, open areas near the communities, clearings and secondary forests, and wild species grow in areas of seasonally flooded wetlands and terra firme ('solid ground') forest, in some cases in locations that are hard to access. Traditional knowledge of plants was found to be falling into disuse presumably as a consequence of the local official health services that treat malaria in the communities using commercial drugs. Despite this, some species are used in the prevention of this disease and also in the recovery after using conventional anti-malarial drugs.

The uniqueness and therapeutic value of natural products from West African medicinal plants, part III: least abundant compound classes

In this review, a continuation of our in-depth coverage of natural products derived from West African medicinal plants with diverse biological activities has been given.

Evaluation of in vivo antimalarial activities of ethanolic leaf and seed extracts of Telfairia occidentalis

The leaves and seeds of Telfairia occidentalis are used as vegetables in making soups in Southern Nigeria. In this study, we investigated the antimalarial activity of leaf and seed extracts in vivo in mice infected with Plasmodium berghei berghei during early and established infections. T. occidentalis leaf extract (250-750 mg/kg/day) exhibited antiplasmodial activity both in the 4-day early infection test and in established infection with a marked increase of the mean survival time, which, however, remained lower than that achieved with the standard drug, chloroquine (5 mg/kg/day). The seed extract (450-1,350 mg/kg/day) also demonstrated a promising blood schizontocidal activity in early and established infections. This plant possesses significant antiplasmodial activities, which may be exploited in the control of malaria.

Antiplasmodial and antidiabetic activities of ethanolic leaf extract of Heinsia crinata

The ethanolic leaf extract of Heinsia crinata, grown particularly for the leaf in Niger Delta region of Nigeria, was evaluated for antiplasmodial activity in Plasmodium berghei-infected mice as well as for hypoglycemic and antidiabetic activities in alloxan-induced diabetic rats. H. crinata (450-1,350 mg/kg/day) exhibited significant (P < .05) blood schizonticidal activity in both the 4-day early infection test and established infection with a considerable mean survival time, though not comparable to that of the standard drug, chloroquine (5 mg/kg/day). Treatment of alloxan-induced diabetic rats with the leaf extract caused a significant (P < .01) reduction in fasting blood glucose levels of normal and alloxan-induced diabetic rats both in an acute study and with prolonged treatment (2 weeks). The activity of the extract was comparable to that of the reference drug, glibenclamide, during the acute study but was not comparable to that of the standard drug during prolonged treatment. The results suggest that the leaf extract of H. crinata possesses significant (P < .05) antiplasmodial as well as hypoglycemic and antidiabetic effects that can be employed in health care.

In vitro cytotoxicity studies of 20 plants used in Nigerian antimalarial ethnomedicine

Twenty plants identified and selected from Southwest and Middle belt Nigerian antimalarial ethnopharmacology were evaluated for in vitro cytotoxicity using the brine shrimp lethality assay. The methanol extracts of 20 plant samples from 11 plant families were subjected to the assay. Of the studied plants, Lippia multiflora and Morinda lucida bark were found to be cytotoxic, with LC(50) values of 1.1 and 2.6 microg/ml, respectively. The least toxic plant extract was Bridelia micrantha (LC(50) value >9.0 x 10(6) microg/ml). Most of the plants were found to be relatively non-toxic.

Prediction of anti-plasmodial activity of Artemisia annua extracts: application of NMR spectroscopy and chemometrics

We describe the application of 1H NMR spectroscopy and chemometrics to the analysis of extracts of Artemisia annua. This approach allowed the discrimination of samples from different sources, and to classify them according to anti-plasmodial activity without prior knowledge of this activity. The use of partial least squares analysis allowed the prediction of actual values for anti-plasmodial activities for independent samples not used in producing the models. The models were constructed using approximately 70% of the samples, with 30% used as a validation set for which predictions were made. Models generally explained >90% of the variance, R(2) in the model, and had a predictive ability, Q(2) of >0.8. This approach was also able to correlate 1H NMR spectra with cytotoxicity (R2=0.9, Q2=0.8). This work demonstrates the potential of NMR spectroscopy and chemometrics for the development of predictive models of anti-plasmodial activity.

Cultural categorization of febrile illnesses in correlation with herbal remedies used for treatment in Southwestern Nigeria

The ethnographic study was conducted in two communities in Oyo State in Southwestern Nigeria. The study sites consisted of a rural and an urban local government area located in the tropical rain forest zone of Nigeria. The study was designed to obtain information on febrile illnesses and herbal remedies for treatment with the aim of identifying potential antimalarial drugs. The study revealed that fever is a general term for describing illnesses associated with elevated body temperature. The indigenous Yoruba ethnic population has categorized fever based on symptoms and causes. The present communication is the result of focus group discussion and semi-structured questionnaire administered to traditional healers, herb sellers, elders and mothers. This was on types of fevers, symptoms and causes of febrile illnesses. The investigation also included use of traditional herbs in the prevention and treatment of the illnesses in the two communities.A total of 514 respondents were interviewed. This was made up of 266 (51.8%) from Atiba local government area (LGA), an urban centre while 248 (48.2%) respondents were interviewed from Itesiwaju LGA, a rural community. The LGAs are located in Oyo State of Nigeria. The respondents proffered 12 types of febrile illnesses in a multiple response answering system in Yoruba language. The most common ones (direct translation into English) were: yellow fever (39.1%), typhoid (34.8%), ordinary (28.8%), rainy season (20.8%) and headache (10.5%) fevers, respectively. Perceived causes of each of the febrile illnesses included stress, mosquito bites, unclean water, rains and over exposure to the sun. Methods of fever prevention were mainly with the use of herbal decoctions, powdered herbs, orthodox medications and maintenance of proper hygiene. Of a total of 112 different herbal remedies used in the treatment of the febrile illnesses compiled from the study, 25 recipes are presented. Recipes consisted of 2-7 ingredients. Oral decoctions (84%), oral powders (63%), use as soaps and creams (40%) in a multiple response system, were the most prevalent routes of administration of prepared herbs used in the treatment of the fevers. Boiling in water or alcohol was the most common method used in the preparation of the remedies. The four most frequently mentioned (multiple response system) plants in the Southwest ethnobotany for fevers were Azadirachta indica (87.5%), Mangifera indica (75.0%), Morinda lucida (68.8%) and Citrus medica (68.8%).

Lansium domesticum: skin and leaf extracts of this fruit tree interrupt the lifecycle of Plasmodium falciparum, and are active towards a chloroquine-resistant strain of the parasite (T9) in vitro

Malaria remains a global problem in the light of chloroquine-resistant strains of Plasmodium falciparum. New compounds are needed for the development of novel antimalarial drugs. Seed, leaf, and fruit skin extracts of Lansium domesticum, a common fruit tree in South-East Asia, are used by indigenous tribes in Sabah, Malaysia for treating malaria. The skin and aqueous leaf extracts of the tree were found to reduce parasite populations of the drug sensitive strain (3D7) and the chloroquine-resistant strain (T9) of P. falciparum equally well. The skin extracts were also found to interrupt the lifecycle of the parasite. The data reported here indicate that extracts of L. domesticum are a potential source for compounds with activity towards chloroquine-resistant strains of P. falciparum.

People's perception of malaria in Mbarara, Uganda

To understand people's perceptions of malaria and their implications for control programmes, we held focus group discussions (FGDs) and conducted semi-structured interviews (SSIs) with community members in Mbarara, Uganda. Mosquitoes were perceived as the cause or transmitters of malaria but the causation/transmission model of people differed from biomedical facts. Convulsions, a common complication of malaria, were perceived as a supernatural ailment, best treated by traditional medicine, as was splenomegaly. More than 70% of the patients with malaria had treatment from non-public health sources. This included self-treatment (13%), use of traditional healers (12%) and use of private medical practitioners/pharmacists (69%). Although 26% (887/3309) used bednets to prevent malaria, only 7% of the nets were impregnated with insecticide. People who did not use bednets cited discomfort because of heat/humidity and their high cost as reasons. To improve malaria control in this area, people need to be educated on the connection between mosquitoes and malaria and on seeking biomedical treatment for convulsions. The malaria control programme could collaborate with traditional and private health care providers to increase promotion of insecticide-impregnated mosquito nets.

Antiplasmodial activities of some Ghanaian plants traditionally used for fever/malaria treatment and of some alkaloids isolated from Pleiocarpa mutica; in vivo antimalarial activity of pleiocarpine

Fourteen Ghanaian plants used in folk medicine to treat fever/malaria were screened for activity against Plasmodium falciparum (strain K1) and were tested for general toxicity to the brine shrimp. Extracts from three of the plants, Pleiocarpa mutica, Cleistopholis patens and Uvaria chamae were found to have significant antiplasmodial activity. The extract of U. chamae was toxic to brine shrimps. These findings lend support to the use of these plants in traditional medicine. Possible toxicity due to U. chamae is a cause for concern. Five known alkaloids, pleiocarpine (1), kopsinine (2), pleiocarpamine (3), eburnamine (4) and pleiomutinine (5) were isolated from the roots of P. mutica. This is the first report of the occurrence of (4) in P. mutica. Compound (5) was the most active against P. falciparum (IC50 = 5 microM). Although (1) was inactive against malaria parasites in vitro, it was moderately active against P. berghei in mice (25 mg kg(-1) daily for 4 days reduced parasitaemia by 28.5% compared to untreated controls).

The potential of Artemisia annua L. as a locally produced remedy for malaria in the tropics: agricultural, chemical and clinical aspects

The plant Artemisia annua L. (Asteraceae) is listed in the Chinese pharmacopoeia as a remedy for various fevers including malaria, and contains the well-established antimalarial compound artemisinin. In this study, a hybrid form of A. annua was successfully cultivated in Central Africa. The aerial parts of the plant contained 0.63-0.70% artemisinin per dry weight, and approximately 40% of this artemisinin could be extracted by simple tea preparation methods. Five malaria patients who were treated with A. annua tea showed a rapid disappearance of parasitaemia within 2-4 days. An additional trial with 48 malaria patients showed a disappearance of parasitaemia in 44 patients (92%) within 4 days. Both trials showed a marked improvement of symptoms. In our opinion, these results justify further examinations of the antimalarial effect of A. annua preparations.