Antimalarial potential of five Nigerian medicinal plants: Repository versus curative activities

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The conventional management of malaria in most endemic areas is based on phytomedicine. It is commonly believed that prevention is better than cure when it comes to disease management. Therefore, medicinal plants commonly used for treatment in herbal medicine are also used for prevention purposes. Hence, it is important to investigate the efficacy of medicinal plants in relation to the timing of their use. To document the medicinal plants used for treating malaria, a structured questionnaire-based ethnobotanical survey was conducted in Omu-Aran, Kwara State, Nigeria. The survey revealed the use of 31 plant species from 24 families, with origin in Omu-Aran, in herbal antimalarial recipes. Some of the identified plants were subjected to in vivo antimalarial bioassays. The aqueous and dichloromethane: Methanol (1:1) extracts of the leaves and stem bark of Morinda lucida and Nauclea latifolia, as well as the leaf extracts of Chromolaena odorata, Tithonia diversifolia, and Lawsonia inermis were tested at doses of 100, 250 and 400 mg/kg against Plasmodium berghei Anka. The repository and curative tests were conducted to assess the residual and curative abilities of the extracts, respectively, with chloroquine as a reference drug. The tested extracts demonstrated better antiplasmodial activities in the repository tests, particularly the aqueous extracts. Only the organic extract of T. diversifolia at 100 mg/kg exhibited a high antiplasmodial activity with a percentage chemosuppression (PCS) value of 66.13%, while other extracts showed moderate (PCS: 30 – 60%) to no activity (PCS: <0%) in curative tests. In repository tests, only N. latifolia showed high activity with percentage chemoprophylaxis (PCP) values ranging from 61.51% to 81.69%, while other extracts generally showed moderate activities. Chloroquine showed strong chemosuppression (92.74 ≤ PCS ≤ 98.77) in curative tests but weak chemoprophylaxis (PCP <30%). The efficacy tests showed that most of the investigated medicinal plants were more effective for prevention rather than for curative purposes.