Abstract:
Phytochemical and antimalarial studies were performed on the leaves of Eupatorium odoratum L., collected along roadsides throughout forest zones in Ratchaburi Province, Thailand. Chloroform extract was found to be active against K1 strain of Plasmodium falciparum in in vitro cultures with an EC50 value of 9.5 μg/ml. Bioassay-guided fractionation of the chloroform extract determined that the subfractions EU3, EU4 and EU5 had antimalarial activities with EC50 values of 30, 23.5 and 25μg/ml, respectively. Further fractionation of these subfractions yielded
three active compounds which through spectroscopy identified as isosakuranetin, kaempferide and tamarixetin, and these showed activities against Plasmodium falciparum at the EC50 values of 45.56, 19.86 and 26.20 μM, respectively. The dihydroartemisinin-potentiating activities of the active compounds were also investigated the results indicated that these three compounds had a potentiating effect on the antimalarial activity of dihydroartemisinin (DHA). This is the first report on both the antimalarial activities of the flavonoids, isosakaranetin, kaempferide and tamarixetin from the leaves of E. odoratum as well as on their potentiating effect on DHA."