Bioactivity-directed evaluation of fruit of Kigelia africana (Lam.) benth. Used in treatment of malaria in Iwo, Nigeria

Abstract

Ethnopharmacological relevanceThe ancient people of Iwo communities consisting of Ile-Ogbo, Olupona, Iwo and Ogbagba continue to engage in the traditional use of medicinal plants for the treatment and management of common diseases especially malaria. Aims of this studyThis study conducted an ethnomedicinal survey of plants used to treat malaria and feverish conditions by the people of Iwo, Nigeria. It also evaluated the antiplasmodial activity of the morphological parts of Kigelia africana (Lam.) Benth., and isolated, as well as characterised pure compounds from the semi-purified fractions of the fruit extract. Materials and methodsThe ethnomedicinal survey was conducted using semi-structured questionnaires administered to only herb sellers in Iwo, Ile-Ogbo, Olupona, and Ogbagba areas of Osun State. Extracts of K. africana morphological parts; leaf, root, stem bark, and fruit were obtained by cold maceration in methanol, followed by assessment of acute toxicity (LD50) and antiplasmodial activity in Plasmodium berghei infected rats using the 4-day suppressive test model. The most active fruit extract was further subjected to activity-guided fractionation and purification using n-hexane, dichloromethane, ethyl acetate (EtOAc), n-butanol (n-BuOH), and methanol (MeOH) in gradients to obtain the semi-purified fractions and two pure isolated compounds using various chromatographic and spectroscopic techniques. Results and discussionFrom the survey, thirty-one plant species were identified for treating malaria in Iwo area. Azadirachta indica leaf was the most frequently used (78.3% of the respondents) while Manihot esculenta leaf (3.33%) was the least. The identified plants are distributed among 24 families, with Anacardiaceae and Asteraceae (11.67% each) been the most occurring families. Kigelia africana (Bignoniaceae) ranked the 6th position with 60% frequency of occurrence. The LD50 values obtained for the extracts were greater than 5000 mg/kg (p.o). The chemo-suppression activity of the extracts at 125 mg/kg was in the order of stem bark (26.59%), leaf (41.75%), root (43.95%), and fruit (54.54%). The semi-purified methanol fraction of the fruit showed the most antiplasmodial activity with a percent chemo-suppression of 69.94 and yielded 4-(2,3-dihydroxypropoxy)-3,5-dihydroxy-5-methylfuran-2-one and sucrose. ConclusionThe use of herbs and medicinal plants either singly or in combination for the treatment of malaria among the people of Iwo community in Nigeria is still well practised. Lack of formal education among most of the respondents and use of same local name for different plants species or plant parts; which often lead to wrong plant collection were among the constrains encountered. Kigelia africana has antiplasmodial activity in the order of fruit > root > leaf > stem bark.