African pear tops list of novel plants for drug-resistant malaria
The season for African pear, local pear or rather native pear is here again! It is usually eaten as snack, but recent scientific findings suggest they might provide the next best anti-malaria drug, toothpaste and skin care product.
Commonly called African pear, native pear or bush butter, Dacryodes edulis belongs to the plant family Burseraceae. It called safoutier in French. In Nigeria, it is ibe in Kalabari; boshu in Bokyi; orunmwun in Edo (indicating something edible); ube in Ibo; orumu in Urhobo; and elemi in Yoruba.
Researchers have identified the compounds responsible for the anti-malarial activity of African pear, Dacryoedes edulis, and their suitability as leads for the treatment of drug resistant malaria.
The study published in PLOS ONE is titled “New Antimalarial Hits from Dacryodes edulis (Burseraceae) – Part I: Isolation, In Vitro Activity, In Silico “drug-likeness” and Pharmacokinetic Profiles.”
According to the study, five compounds were isolated from ethyl acetate and hexane extracts of D. edulis stem bark and tested against 3D7 (chloroquine-susceptible) and Dd2 (multidrug-resistant) strains of Plasmodium falciparum, using the parasite lactate dehydrogenase method.
Cytotoxicity studies were carried out on LLC-MK2 monkey kidney epithelial cell-line. In silico analysis was conducted by calculating molecular descriptors using the MOE software running on a Linux workstation.
The “drug-likeness” of the isolated compounds was assessed using Lipinski criteria, from computed molecular properties of the geometry optimized structures. Computed descriptors often used to predict absorption, distribution, metabolism, elimination and toxicity (ADMET) were used to assess the pharmacokinetic profiles of the isolated compounds.
Anti-plasmodial activity was demonstrated for the first time in five major natural products previously identified in D. edulis, but not tested against malaria parasites.
The most active compound identified was termed DES4. It had IC50 values of 0.37 and 0.55 µg/mL, against 3D7 and Dd2 respectively. In addition, this compound was shown to act in synergy with quinine, satisfied all criteria of “Drug-likeness” and showed considerable probability of providing an antimalarial lead.
The remaining four compounds also showed anti-plasmodial activity, but were less effective than DES4. None of the tested compounds was cytotoxicity against LLC-MK2 cells, suggesting their selective activities on malaria parasites.
The researchers concluded: “Based on the high in vitro activity, low toxicity and predicted “Drug-likeness” DES4 merits further investigation as a possible drug lead for the treatment of malaria.”
They added: “The emergence and spread of resistance to frontline anti-malarials is a real challenge to malaria control, which can be addressed by expanding the arsenal of antimalarial products. Medicinal plants are well known sources of antimalarials. Over a thousand plant species are commonly used across Africa for prevention and/or treatment of malaria symptoms, and some of these had been revealed as housing uniquely effective antimalarial. The examples of quinine and artemisinin isolated from Cinchona species and Artemisia annua -source of Artemisinin Combination Therapies (ACTs)- are highly illustrative.
“Dacryodes edulis is an evergreen tree attaining a height of 18 to 40 metre in the forest but not exceeding 12 metre in plantations. The plant, which can be cultivated widely (since it adapts well to differences in the duration of day light, temperature, rainfall, soils and altitude), is a multipurpose plant in African folk medicine.
“In traditional medicine, different preparations of parts of the plant are used variously in Nigeria and the Democratic Republic of Congo to treat several diseases including parasitic skin diseases, jigger, mouthwash, tonsillitis, sickle cells disease, arthritis, wounds and malaria. It is taken in a powdered form with maleguetta pepper (Aframomum melegueta) as an anti-dysenteric, for anaemia and oral bleeding. With palm oil, it is applied topically to relieve general pains and stiffness, and to treat skin diseases.
“A decoction of the root bark is drunk for leprosy. Leaf sap is instilled into the ear for ear problems, and a leaf decoction is used to prepare a vapour bath for fevers and headache. In the West region of Cameroon, where this plant is locally called Zo’o (Batcham), the leaves and the stem bark of D. edulis are boiled with leaves of Cymbopogon citratus (lemon grass) and Mangifera indica (mango) in water to give a decoction against malaria. In spite of its rich ethno-pharmacology, there is data on its anti-plasmodial activity.
“Previous investigations demonstrated the analgesic, anti-inflammatory, anti-allergic, anti-cancer and antimicrobial and antimalarial activity of D. edulis, and significant anti-plasmodial activity had also been recorded for this plant, with IC50 below 10 µg/mL on drug resistant malaria parasites. However the bioactive ingredients were yet to be identified. Moreover, the stem bark which is preferably employed in Cameroonian folk medicine is still to be fully investigated.”
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