Stage Specificity of Eurycomanone Isolated from Eurycoma longifolia on Plasmodium falciparum Cycles

Eurycomanone is the most active compounds in the roots of Eurycoma longifolia and shown to have in vitro antiplasmodial activity. However, the stage of Plasmodium falciparum cycles which are sensitive to eurycomanone have not been investigated. This study was conducted to investigate stage specificity of eurycomanone at various stages of P. falciparum life cycles. Stage specificity of eurycomanone at various stages of P. falciparum was performed on P. falciparum culture in vitro. A total of 100 µL of solution containing P. falciparum at ring stage after synchronized with 1-2% parasitemia (hematocrit 3%) were included in 96 wells microcultures and then added 100 µL of solution containing eurycomanone with 6 various concentrations. The specificity of eurycomanone was evaluated microscopically by counting the percentage of each stage of P. falciparum after for 8, 16, 24, 32, 40, 48, 56, 64 and 72 h incubation time, compared with control without any compound. The results showed that eurycomanone can kill ring stage of P. falciparum and may inhibit the development of young schizont to mature schizont in vitro. However, it needs further investigations for the mechanism.