A Study of the Antimalarial Activity of Combined Plant Extracts Traditionally Used in Kenya

Abstract

Introduction: Due to resistance and cost of current antimalarial drugs in use, there is need to continue searching for effective and affordable treatment for this disease. Traditional medicinal plants have been focused on as source of such drugs. Methodology: For this study, combined crude extracts from six plants used in Kenya were tested in vitro against chloroquine resistant Plasmodium falciparum W2 strain using the [3H] hypoxanthine uptake assay and in vivo using Plasmodium berghei on mice. Cytotoxicity tests were done using the MTT based colorimetric assay on Vero 199 and selectivity index used to assess safety of the extracts with the best activity. Results: In vitro results with combinations involving Zanthoxylum chalybeum with four of the extracts indicated activity below IC50 10µg/ml. A combination of S. pinnata and Toddalia asiatica extracts exhibited the best activity in vivo having a parasite growth suppression of 81.3% at a dose of 500mg/kg. S. pinnata and T.asiatica combination had CC50 values of 102.93±5.96µg/ml and >1000µg/ml with selectivity indices of 9.52 and 15.24 respectively, indicating good therapeutic potential due to their safety margins. Conclusion: The results obtained from both in vitro and in vivo tests support the use of the plants selected in traditional treatment of malaria. A combination of methanol fruit extract of T. asiatica and methanol whole plant extract of S. pinnata showed promising parasite growth suppression against P. berghei that was comparable with Artemether and was synergistic on in vitro testing against chloroquine- resistant W2 strain of P. falciparum.