Bitter leaf, delightful soup, cure for malaria?
The leaves of Vernonia amygdalina, popularly known as bitter leaf, are usually bitter and all parts of the plant (leaves, stem and roots) are said to have medicinal uses. These include promotion of dieresis, cure of tonsillitis, fever, diabetes, pneumonia, jaundice, anaemia, stomach problem and ascaris.
In a study, researchers studied the antimalarial activities of the aqueous and ethanolic crude extracts of bitter leaves, already in use by traditional healers to treat malaria and other diseases.
The researchers found that under laboratory conditions, extracts of bitter leaf made from water and ethanol showed moderate antimalarial activity and a negligible level of toxicity in the test animals–rats.
Malaria is one of the most important tropical diseases and the greatest cause of hospitalisation and death among children below age of five years. The World Health Organisation (WHO) reported that there were an estimated 246 million malaria cases distributed among 3.3 billion people at risk in 2006, causing at least a million deaths. These were mostly children under five years.
WHO said approximately 80 per cent of malaria cases in the world are estimated to be in Africa where the disease is endemic. In Nigeria, malaria transmission occurs all-year-round in the South, and is more seasonal in the North.
The alarming rate at which Plasmodium falciparum has developed resistance to chloroquine and other synthetic antimalarial drugs makes it necessary to search for more effective antimalarial compounds.
In Africa and other countries where malaria is endemic, traditional medicinal plants are frequently used to treat or cure malaria, thus the need to investigate the antimalarial activity of medicinal plants in order to determine their potentials as sources of new antimalarial agents.
The study entitled “In vitro Antimalarial Activity of the Extracts of Vernonia Amygdalina” was documented in the 2011 edition of the Science World Journal. It was carried out by Sha’a, K. K from the College of Science and Technology, Adamawa State Polytechnic; Oguche, S from the Department of Paediatrics, Jos University Teaching Hospital, Jos; Watila, I. M from the Department of Paediatrics, State Specialist Hospital, Maiduguri, Borno State, as well as Ikpa, T. F. from the Department of Wildlife, University of Agriculture, Makurdi.
For the study, blood samples were collected from children and adults aged six months and above, who had fever in the last 24 hours, auxiliary temperature of 37.5 C, had not taken any antimalarial in the last two weeks, and who gave oral or written informed consent after the aim of the study were involved in the study. These were patients attending the outpatient department of the Damboa General Hospital, Borno State.
Of the two extracts tested, the ethanol extract of bitter leave showed the highest antimalarial activity of 78.1 per cent. The water extract had the malaria parasite growth inhibition of 74.0 per cent.
In addition, dose-dependent antimalarial activity was clearly shown for the two crude extracts. The percentage inhibitions are higher with increasing concentrations.
Previously, the antimalarial activity of bitter leaf against resistant P. berghei had been reported by scientists in the British Journal of Biomedical Science. In their findings, leaf extract produced 67 per cent suppression of malaria –causing germ in a four day test.
In addition, a another study pointing to the potential use of bitter leaf in formulating a malaria drug in years to come, revealed its potential also in reversing chloroquine resistance when used as an adjuvant with chloroquine.
The 2008 study, documented in the journal African Health Sciences, while validating the traditional use of bitter leave in the treatment of malaria in Nigeria reported that the aqueous extract of the plant enhance the antimalarial effects chloroquine in mice infected with chloroquine resistant and sensitive P. berghei strains.
Previously, a 2010 study documented in the African Journal of Traditional, Complementary and Alternative Medicines stated that African mahogany, in combination with chloroquine or halofantrine, elicited significantly greater malaria parasite clearance following the administration of the combination when compared to the effects of African mahogany or the conventional drugs alone.
The study was entitled “Chemotherapeutic interaction between Khaya Grandifoliola stem bark extract and two anti-malarial drugs in mice.” It was carried out by Steve O Ijarotimi; Joseph M Agbedahunsi; Clement O Adewunmi and Cyprian O Onyeji, all researchers at the Obafemi Awolowo University, Ile-Ife, Osun State.
Similarly, a review of studies into medicinal plants used to treat malaria across all ethnic and cultural groups in Nigeria showed that there were more than 110 plant varieties. The review entitled: “Medicinal plants used in Nigeria for treatment of malaria” was documented by the 2011 edition in the Journal of Ethnopharmacology. It involved J.O Adebayo from the Department of Biochemistry, University of Ibadan in collaboration with A.U Krettlia.
They include plants such as leaves of Newbouldia laevis (Akoko leaf in Yoruba), Enatia chlorantha (African yellow wood, Iyani or Awopa in Yoruba), Eupatorium odoratum (ogbogbo or Ibo- ofo in Yoruba), Bridelia micrantha (abere-aluko or akisan in Yoruba), Cajanus Cajan (Pigeon pea in English, olele in Edo, shingwazo in Gwari), Carica papaya (pawpaw).
In addition, there were also stem bark of plants such as Abrus precatorius (omisinmisin in Yoruba), Afzelia Africana (Mohogany bean tree), Psidium guajava (guava), cashew plant, Blighia sapida (Achee, Akee, Akee or Apple Tree), Alchornea cordifolia (baushe in Hausa, edo in Igbo and idi-odan in Yoruba). Also on the list were stems of Citrus sinensis (sweet orange), Cymbopogon giganteus (Oka eye in Yoruba), Khaya senegalensis (African mahogany, madachi in Hausa and ono in Igbo), Mangifera indica (mango) as well as onion bulbs and ginger.
Alstonia boonei (awun in Yoruba) is highly priced, especially in situations where affordable antimalarial drugs are found ineffective, due to drug-resistant malaria parasites. The plant stem bark or leaves are administered as decoction or “teas” and sometimes as an ingredient in malaria “steam therapy”.
Recently, researchers in the 2008 edition of Tropical Journal of Pharmaceutical Research, formulated the stem bark extract of this plant into tablets, and made this available as an antimalarial remedy.
Most of these antimalarial plants are used in form of monotherapy, and only a few plants are taken together in combined therapies. An example is the multi-herbal extract referred to as ‘Agbo-Iba’ made up of Cajanus cajan (pigeon pea) leaf, Euphorbia lateriflora leaf, mango leaf and bark, Cassa alata leaf(Asunwon in Yoruba), Cymbopogon giganteus leaf, Nauclea latifolia leaf, and Uvaria chamae bark.
Pharmacological studies have demonstrated under laboratory conditions antimalarial effects of extracts from 45 plant species used in Nigerian folk medicine out of the 51 species tested. These include neem, Morinda lucida (brimstone tree, oruwo in Yoruba and eze-ogu in Igbo), African mahogany, Tithonia diversifolia (Wild Sunflower; ogbo or Agbale in Yoruba), Momordica balsamina (Balsam pear or ejinrin in Yoruba) and Picralima nitida (abere in Yoruba).
Previous studies on neem, attributed its antimalarial effect to it affecting all stages of the malaria parasite in the body unlike artemisinin and primaquine that seem to affect only the immature stages of the malaria parasite.
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