PLANTS OF THE ANNONACEAE TRADITIONALLY USED AS ANTIMALARIALS : A REVIEW 1

ABSTRACTSpecies of the Annonaceae family are used all over the tropics in traditional medicine in tropical regions for the treatment of malaria and other illnesses. Phytochemical studies of this family have revealed chemical components which could offer new alternatives for the treatment and control of malaria. Searches in scientific reference sites (SciFinder Scholar, Scielo, PubMed, ScienceDirect and ISI Web of Science) and a bibliographic literature search for species of Annonaceae used traditionally to treat malaria and fever were carried out. This family contains 2,100 species in 123 genera. We encountered 113 articles reporting medicinal use of one or more species of this family including 63 species in 27 genera with uses as antimalarials and febrifuges. Even though the same species of Annonaceae are used by diverse ethnic groups, different plant parts are often chosen for applications, and diverse methods of preparation and treatment are used. The ethanol extracts of Polyalthia debilis and Xylopia aromatica proved to be quite active against Plasmodium falciparum in vitro (median inhibition concentration, IC50 < 1.5 μg/mL). Intraperitoneal injection of Annickia chlorantha aqueous extracts (cited as Enantia chlorantha) cleared chloroquine-resistant Plasmodium yoelii nigeriensis from the blood of mice in a dose-dependant manner. More phytochemical profiles of Annonaceous species are required; especially information on the more commonly distributed antimalarial compounds in this family.


INTRODUCTION
Malaria and the Annonaceae family: The annual death of thousands of people worldwide due to malaria has made this disease one of the major problems in world health.This has motivated the development of research into new alternatives for the control and cure of this disease.Evidence for this is the diverse number of publications on screenings based on traditional medicine in Africa, India and South America regions where malaria is endemic and on the search for natural products derived from plants.Phytochemical studies are also important in this context for revealing natural products which may later be developed into new drugs.New antimalarials are needed because Plasmodium falciparum and P. vivax, the two main parasites responsible for malaria infections in humans, are becoming resistant to the two major classes of effective drugs, namely quinoline and artemisinin antimalarials.One of the main problems in malaria control is that this disease is endemic to generally poor and underdeveloped countries in tropical and subtropical regions of the world.These regions and their problems are not in general of major interest to the economically more developed countries.In this sense, part of the population which inhabits areas where malaria is endemic does not have access to efficient health services and sometimes the only source of therapeutic treatment is based on plants.Among the families which stand out due to their broad traditional uses against malaria is Annonaceae (order Magnoliales).This family is distributed pantropically and comprises approximately 123 genera and 2,100 species (MABBERLEY, 2008) of trees, shrubs and lianas.The antiprotozoal activity of Annonaceae species in traditional treatments of malaria, Chagas disease (American trypanosomiasis) and leishmaniasis is associated with secondary metabolite alkaloids, acetogenins, sterols and terpenes found in different parts of these plants ( OCAMPO & OCAMPO, 2006).This review covers ethnobotanic reports on Annonaceous species used traditionally to treat malaria and related symptoms (high and intermittent fevers, chills, headaches, body pain, liver ailments) and ethnopharmacologic studies demonstrating in vitro activity of extracts of plants of this family against Plasmodium falciparum (median inhibition concentrations, IC 50 < 1.5 µg/mL) and other malaria parasites.

MATERIAL AND METHODS
Information on publications in the scientific literature was obtained using the SciFinder Scholar (2007) program and the input phrase "Antimalarials from Plants" which produced a list of publications from 1942 (first publication) to June, 2011.A list of 765 abstracts was initially obtained and further refined by restricting plants to the Annonaceae family.In similar fashion, references were found on the Scielo, PubMed, ScienceDirect and ISI Web of Science websites using the input phrase "antimalarials plants Annonaceae" in January, 2013 .Also, online searches were performed at different sites and at libraries at the Federal University of Amazonas in Manaus, Brazil, National Institute for Amazon Research in Manaus and University of La Amazonia in Colombia.The data were organized in a spreadsheet.Information registered in the spreadsheet included species names, geographical distribution, regions where the plant is used, preparation methods and parts of the plant used as antimalarials, as febrifuges, for headaches, liver problems, etc.. Also, where available, data on in vitro median inhibitory concentrations (IC 50 ) and in vivo activities against Plasmodium spp.used in literature studies were included.

RESULTS AND DISCUSSION
Traditional uses of Annonaceae: Different ethnic groups have used species of Annonaceae as a therapeutic source to combat malaria.While some species are not useful for the treatment of malaria per se they are used to treat the symptoms.
In the present study, 63 species belonging to 27 genera were found in literature studies.In general, these plant species were used to treat the disease or its symptoms in countries in the Amazon region (northern South America); Africa, Central America, India and Malaysia (see Table 1).Eleven antimalarial species each for the genera Annona and Xylopia made these the most represented of the Annonaceae family.These genera have a pantropical distribution.They also are known to produce antimalarial alkaloids (FISCHER et al., 2004;GARAVITO et al., 2006).
The genus Annona: Well-known for its edible fruit.Annona muricata is the most widely used species worldwide in traditional medicine, as foodstuff and in the cosmetic industry.A. muricata ANNONACEAE PLANTS TRADITIONALLY USED AS ANTIMALARIAL... was by far the most commonly cited Annonaceous plant for the treatment of malaria, fevers, liver ailments and headaches.Nineteen literature sources made reference to the use of roots, bark, fruit and leaves of this species in the preparation of therapeutic remedies among the peoples of India, Madagascar, Indonesia, Costa Rica, Barbados and a few countries from Africa and South America.Of the nineteen sources of literature reporting the use of A. muricata, twelve indicated use against fever and five reported specific use against malaria.The only reported use of this species for the curing of liver problems was by Hidalgo (2003) who observed the use of the bark of this species among the traditional riverine populations in the Brazilian Amazon.Also, populations along the Pacific coast of Colombia place leaves on the forehead of the sick person for the treatment of the headaches caused by malaria infections (BLAIR & MADRIGAL, 2005).In Colombia, decoctions are prepared from fresh or dry leaves of A. muricata and drank to treat the feverish state brought on by malaria infections (GÓMEZ-ESTRADA et al., 2011).

Annona squamosa:
This species is known by the local name Sita phol and is cultivated in communities in Northeastern India.The fresh leaves of this plant are used together with Ocimum americanum and O. gratissimum (Lamiaceae) for the treatment of malaria in different communities found in Africa (KAOU et al., 2008).This species has other uses related to the control of malaria (and other insect-born diseases) such as repellency against Culicidae, Muscidae and Dictyoptera.

Xylopia:
The medicinal properties and usefulness for the control of agricultural pests, mites, insects and nematodes of species of this genus have been studied (PONTES et al., 2007).Nine species are specifically used to treat malaria and two are used specifically to treat fevers among the local populations of Cameroon Colombia, Brazil, Peru and French Guiana.Generally, the fruit, bark and other aerial parts are used in the preparation of the traditional remedies made from plants of this genus.In Cameroon Xylopia aethiopica, commonly named Ethiopian Pepper is the only species of this genus claimed to be useful for the treatment of malaria and other diseases.For treatment of malaria, a decoction is prepared from a teaspoon of bark crushed in a liter of water and then drank.For the treatment of fevers, the same procedure is applied to the dry fruit (TSABANG et al., 2011).Also against fever, Grenand et al. (1987) reported the use of Xylopia frutescens among the Wayãpi Indians of French Guiana.Xylopia aromatica is also reported to be useful for the treatment of malaria by local populations in the region around the Brazilian Federal Capital, Brasília (MESQUITA et al., 2007).
Other genera: 43 additional species representing 23 genera of Annonaceae have been reported in the literature for the treatment of fevers, malaria and headaches, although none of these were indicated for the treatment of liver problems related to malaria.In the Colombian Amazon region, the Tikuna use a decoction of the bark of Cymbopetalum brasiliense for the treatment of fevers (SCHULTES & RAFFAUF, 1994) and a decoction of the external bark of Duguetia duckei is used by Tiriyó communities in the Brazilian state of Pará (CAVALCANTE & FRIKEL, 1973).Guatteria discolor bark is used in a bath among the Wayãpi Indians of French Guiana for the same purpose (GRENAND et al., 1987).Schultes and Raffauf (1994) reported the use of the bark of Guatteria schunkevigoi among the local populations in the Napo region of Ecuador.In the procedure described, the bark is ground and mixed with water and rubbed on the body to combat fevers.The same method is used for the preparation of Guatteria discolor among the Wayãpi populations in French Guiana, though in this case the Wayãpi decoct the bark (GRENAND et al., 1987).In Cameroon, a decoction of the stem bark (500 g) of Duguetia staudtii obtained by scraping the bark with a large knife, or leaves (100 g) soaked in water for 20 min are used in the preparation of a drink which is taken to treat headaches.Similarly, a decoction of leaves (100 g) in water (3 L, 20 min) is used for bathing the head (TSABANG et al., 2011).Desmos teijsmanii and Monodora tenuifolia are used to treat similar aches in Malaysia and Cameroon, respectively (KULIP, 2003;TSABANG et al., 2011).

Preparations and plant parts utilized in traditional remedies:
Different plant parts and methods of preparation are utilized in traditional therapies involving Annonaceous plants.Some methods of preparation are reported more frequently than others.Also, some authors do not provide G. FRAUSIN et al.
information on the methods of preparation.Other authors provide varying degrees of information on these preparations.Most of the sources consulted presented information on preparations involving plant materials that were vague regarding the dosages and the duration of the treatment involving Annonaceae-derived botanicals.The bark is the part of Annonaceae plants which is most often reported in the literature containing descriptions of the preparation of traditional remedies, followed by the leaves and then fruit.The seeds and roots were cited only twice each as being used for remedies.Flowers were used in only one preparation, that involving Cananga odorata, for the treatment of malaria infections.Infusions and decoctions are the methods of preparation of the remedies used in the most common treatments.Administration by mouth is by far the most common route used for Annonaceae traditional remedies.Lannuzel et al. (2002) suggest that alkaloids from A. muricata can modulate the function and the survival of dopaminergic nerve cells in vitro.There are indications that annonacine, found in large quantities in A. muricata, can diminish the levels of ATP in (mesencephalic-derived) dopaminergic cells of rat embryos (LANNUZEL et al., 2003).
Some traditional formulations of Annonaceae plants involve the addition of other plant species.Thus, the roots of Annona muricata are boiled together with those of Blumea balsamifera (Asteraceae), Cymbopogon citratus and Imperata cylindrica (Poaceae) and the aromatic vapor is used to heat the body of people who suffer from high fevers in kadazandusun communities in Malaysia (FASIHUDDIN & GHAZALLY, 2003).Topical applications in the form of baths, although less frequently used, are advised for the treatment of fevers and headaches (as indicated above).Another form of treatment involves the vapours of baths with Annona ambotay and A. haematantha (GRENAND et al., 1987).In French Guiana, the Wayãpi Indians use Annona ambotay leaves and bark crushed, grated and rubbed on the body.They also boiled this plant in a pot and placed the boiled mixture beneath a hammock as vapour bath for the treatment of fever (GRENAND et al., 1987).
The in vitro antimalarial activity of essential oils (Table 2) has been attributed to sesquiterpenes which are among the major components.Boyom et al. (2003) reported that the essential oil obtained from the bark of Duguetia confine (cited as Pachypodanthium confine) was approximately 88% sesquiterpenes and 0.64% aromatic substances.Also, these authors found that the essential oil obtained from the bark of Xylopia aethiopica contained ca.45% sesquiterpenes and the essential oil extracted from the bark of Xylopia phloiodora contained approximately 88% sesquiterpenes and 3% aromatic compounds.The essential oil of Cleistopholis patens contained 81% sesquiterpenes and the major components of the bark essential oil were: a-copaene, d-cadinene, and germacrene D; the major components of the leaf essential oil were: b-caryophyllene, germacrene D, ANNONACEAE PLANTS TRADITIONALLY USED AS ANTIMALARIAL... and germacrene B (BOYOM et al., 2011).The genus Uvaria has undergone extensive study related to its in vitro antimalarial activity making it arguably the most studied among Annonaceae genera for this kind of biological activity (Table 1).Nkunya et al.
(1991) described a study of nine species of Uvaria in which the following antimalarial substances were isolated: uvaretin, diuvaretin and (8',9'-dihydroxy)-3-farnesylindole (IC 50 = 3.5, 4.2 and 2.7 μg/mL, respectively, against the K1 strain of P. falciparum. In their review on natural products from traditionally used antimalarial plants, Bero and Quetin-Leclercq (2011) reported that the antiplasmodial substance (+)-3-acetylaltholactone was isolated from the extracts of the flowers of Goniothalamus laoticus Bân and exhibited in vitro activity against the K1 strain of P. falciparum (IC 50 = 9.5 μM).In vivo activity was observed for another Annonaceous species, Annickia chlorantha (cited as Enantia chlorantha), which is found in Nigeria and other parts of West Africa.The aqueous extracts of this plant were administered intraperitoneally and cleared chloroquine-resistant P. yoelii nigeriensis infections from the blood of albino mice in a dose-dependant manner (KIMBI E FAGBENRO-BEYIOKU, 1996).

Geographic distribution:
The reports on the use of Annonaceae for combatting malaria infections and symptoms of this disease are all from pantropical areas and are obviously the fruit of local experiences in countries where malaria is endemic.Most of the reports available are concentrated in traditional populations of South America and some African countries.The use of species of Annonaceae and other families is directly related to their natural distribution.One example is species of the genus Annona.These species are now found throughout the tropics and are used by peoples in Africa, Central and South America, India and several Caribbean countries.Another example is species of Xylopia used among the populations of Brazil, Cameroon, Colombia, French Guiana, Peru, and Togo.Interestingly, the genus Guatteria has a Neotropical distribution and is restricted in use to traditional populations in the Amazonian regions of Brazil, Colombia, Ecuador and Guyana.In Brazil in particular, there is a broad use of plants from the Annonaceae represented by seven species in five genera.Overall, the genus Annona is represented by ten species and is by far the most important antimalarial genus of this family.

G. FRAUSIN et al.
TABLE 1-Data on the antimalarial and related uses of Annonaceae plant species.

CONCLUSION
The Annonaceae family is rich in potential as a source of chemical entities for the development of novel antimalarial drugs.Several species belonging to this family have been well studied and have provided active antimalarial substances.On the other hand, a large number of species traditionally used to treat malaria from this family have not been studied so far, thus no chemical or pharmacological data are available.Intensification of research in the area of natural products chemistry together with screening for antimalarial activity could provide the lead compounds necessary for new drug development, a result which is awaited by the populations of endemic areas all over the world.