Activity of selected phytochemicals against Plasmodium falciparum

According to the WHO, in 2008, there were 247 million reported cases of malaria and nearly one million deaths from the disease. Parasite resistance against first-line drugs, including artemisinin and mefloquine, is increasing. In this study the plant-derived compounds aglafolin, rocaglamid, kokusaginine, arborine, arborinine and tuberostemonine were investigated for their anti-plasmodial activity in vitro. Fresh Plasmodium falciparum isolates were taken from patients in the area of Mae Sot, north-western Thailand in 2008 and the inhibition of schizont maturation was determined for the respective compounds. With inhibitory concentrations effecting 50%, 90% and 99% inhibition (IC₅₀, IC₉₀ and IC₉₉) of 60.95nM, 854.41nM and 7351.49nM, respectively, rocaglamid was the most active of the substances, closely followed by aglafoline with 53.49nM, 864.55nM and 8354.20nM. The activity was significantly below that of artemisinin, but moderately higher than that of quinine. Arborine, arborinine, tuberostemonine and kokusaginine showed only marginal activity against P. falciparum characterized by IC₅₀ and IC₉₉ values higher than 350nM and 180μM, respectively, and regressions with relatively shallow slopes S>14.38. Analogues of rocaglamid and aglafoline merit further exploration of their anti-plasmodial activity.