Faculty: Pharmaceutical Sciences
Department: Pharmacognosy And Traditional Medicine
Anowi, C. F.
Despite the availability of drugs for malaria, the disease is still one of the most important infectious diseases of humans. With reports of decreased sensitivity to current first line drugs, there arises the need for newer drugs to combat this problem. This has led to increase in research in the investigation of a new alternative source for treatment of malaria including medicinal plant. This study is part of efforts and resources geared towards the malaria control in Nigeria, where the burden of malaria is greatest in Africa due to the large population. In this study, nine Nigerian medicinal plants: Kigelia africana, Baphia pubescens, Morinda lucida, Synclisa scabrida and Buchholzia coriaceae, Rauwolfia vomitoria, Nauclea latifolia, Anthocleista djalonensis and Moringa oleifera were preliminarily evaluated for antimalarial property. Crude methanol extracts of the plants were prepared by cold maceration of the dried and powdered leaves. Preliminary phytochemical screening and antimalarial assay of the plants were carried out using standard methods. The plant with the most effective antimalarial activity was selected, extracted and fractionated using n-hexane, ethyl acetate and n-butanol. The fractions were tested for their antimalarial property, and the most active fraction was subjected to vacuum liquid chromatography (VLC) using solvent mix with varying polarity. The resulting subfractions from the VLC were tested for their antimalarial property, and the most effective were subjected to size exclusion chromatography (Sephadex). These Sephadex subfractions were bulked up with the aid of TLC and UV light to get 19 subfractions which were subjected to HPLC-DAD analysis. In the preliminary studies, the nine plants tested showed varying degree of anti-malarial property. At 100 mg/kg each of them had the following percentage curative effect – A. djalonensis 54%, M. oleifera 58%, S. scabrida 78%, B. coriaceae 78%, N. latifolia 81%, M. lucida 85%, K. africana 90%, R. vomitoria 92%, and B. pubescens 97%. B. pubescens was selected for further investigations because of its promising antimalarial activity and safety at (LD50) 5000/kg. Results of microscopic examination showed that the leaves contain trichomes, spiral xylem vessels and anomocytic stomata. The extractive values fall within normal range. The main phytochemical constituents detected in the ethyl acetate fraction include - tannins, carbohydrates, saponins, flavonoids, alkaloids, and glycosides. Results of the antimalarial screening of the n-hexane, ethyl acetate, and n-butanol fractions of B. pubescens showed that the ethyl acetate fraction was the most effective with almost 100% cure at 100 mg/kg. This ethyl acetate fraction was subjected to VLC and Sephadex separation techniques and some sub-fractions were obtained. These subfractions were subjected to antimalarial screening. HPLC-DAD analysis of the active subfractions of B. pubescens ethyl acetate fraction revealed the presence of citreodimene F, a sesquiterpene lactone. Since sesquiterpene lactone are generally known for their antimalarial properties, citreodimene F may be responsible for the antimalarial property of the plant. Also, the abundance of palitantin, an antiprotozoal agent with antileishmania properties, was revealed. This compound may confer an antileishmanial activity on the plant. Other biologically active compounds detected include aureonitol, cytosporin D, septicine, cerebroside, and shanzhiside methyl ester. The results of this work justify the empirical use of B. pubescens in traditional medicine for the treatment of malaria. It is hoped that the information and data present herein will be useful in rolling back this disease.