Synergistic antiplasmodial activity of artemisia annua fractions against in vitro cultures of plasmodium falciparum
Kangethe, Lucy N.
Nganga, Joseph K.
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Background: Artemisia annua has a very rich phytochemistry comprising several classes of compounds, mainly monoterpenes, sesquiterpenes, and flavonoids. It has been used in China for about 2000 years in the treatment of fever. Objective: The aim was to determine if there is any synergistic effect on the Artemisia annua phytochemicals. Materials and methods: Artemisia annua used in this study was obtained from a hybrid of the plant grown in the Tanzania highlands (2000-2200 m altitude) in Arusha by Natural Uwemba System for Health (N.U.S.Ag). The dried leaves were ground, and sequentially extracted with hexane, dichloromethane (DCM), methanol and water and the extracts were then combined. The extract was then fractionated using high performance liquid chromatography (HPLC). The effect of the combined crude extract was tested at different doses on in-vitro cultures (a CQ sensitive isolate D6 and CQ resistant isolate W2) of Plasmodium falciparum. The fractions and different blends of these were tested at different doses to determine their role, if any, on the activity of the full blend of the plant. Results: Of nine fractions thus tested against D6 and W2, four had activities of less than 3.9μg /ml, three fractions had activities of between 4.77-14.76 μg/ml and the remaining two had activities above 250g/μml. The seven more active fractions were re-evaluated in a subtractive bioassay procedure, in which one of each fraction was excluded at a time from the full 7-component blend. The activity of the combined seven active compounds was 10.40+0.50 μg/ml against W2. Of these, one showed IC50 of less than 3.9 μg/ml and all blends showed IC50 at below 27μg/ml. Conclusion: The results show that different components of A. annua contribute to the synergistic anti-Plasmodium activity. The results constitute a useful basis for identifying the components of the plant other than artemisinin that contribute to the activity of herb.