Abstract

ANTIPLASMODIAL ACTIVITY, CYTOTOXICITY AND ACUTE TOXICITY OF ZANTHOXYLUM CHALYBEUM ENGL

David Njenga*, Beatrice Irungu, James Mbaria, Charles Mutai, Joseph Nguta

ABSTRACT

Ethnopharmacological relevance: Many plants have been used for centuries to treat malaria and useful drugs have been developed from them including quinine and artemisinin based compounds. Zanthoxylum chalybeum (ZC) is still being used today in East Africa in its natural form. Aim of the study: To evaluate the antiplasmodial activity of dichloromethane:chloroform extracts of ZC and their ethyl acetate: petroleum ether fractions, cytotoxicity against Vero 199 cells and lethal dose (LD50). Place and Duration of Study: Center for Traditional Medicine Drug Research (CTMDR), Kenya Medical Research Institute (KEMRI), and University of Nairobi, Kenya, between November 2013 and July 2014 Materials and methods: Dichloromethane:chloroform (1:1) extracts of the stem bark, leave and root bark were fractionated into six fractions each by vacuum liquid chromatography (VLC) using solvent mixtures of increasing polarities; F1 (5% ethylacetate/Petroleum ether), F2 (20% ethylacetate/Pet ether), F3 (40% ethylacetate/Pet ether), F4 (70% ethylacetate/Pet ether), F5 (20% methanol/Pet ether) and F6 (100% methanol). Antiplasmodial activity was investigated using invitro semi-automated Microdilution technique against the chloroquine resistant W2 and sensitive D6 Plasmodium falciparum strains. In vitro cytotoxicity (CC50) was carried out on vero 199 cells at a starting concentrations of 100μg/ml with serial threefold dilution and acute toxicity Acute toxicity test was done in mice at 5000mg/kg. Results: The polar fraction from the root bark and stem bark of Z. chalybeum showed the best antiplasmodial activity at 0.78±0.048μg/ml and 6.0±0.560 μg/ml. They both had CC50 of >100 μg/ml and Lethal dose-50 (LD50) >5000mg/kg. Conclusion: These findings validate the use of ZC in traditional medicine in malaria treatment and further identified the roots and stem bark as the most active and quantified its activity and safety.

Keywords: Plasmodium falciparum, Z. chalybeum, fractions, selectivity index, LD50.