Bioassay-guided fractionation and in vitro antiplasmodial activity of ethyl acetate fractions from Alectryon serratus (Sapindaceae) leaf

Purpose: To investigate the antimalarial activity of active fractions from Alectryon serratus leaves and identify their secondary metabolites. Methods: Fractionation of ethyl acetate fraction from Alectryon serratus leaves was conducted using column chromatography. Five serial concentrations (10, 1, 0.1, 0.01 and 0.001 μg/mL) of each subfraction were tested in vitro against Plasmodium falciparum 3D7 (chloroquine-sensitive). The active subfractions were separated using preparative TLC. Crude isolates were administrated to P. falciparum culture and incubated for 48 h. The percentages of growth inhibition and IC50 were calculated. Secondary metabolites group of sub-fractions and the crude isolate were determined using TLC, FTIR, and UV-VIS spectrophotometry. Chloroquine was used as a standard drug for antiplasmodial testing. Results: Four sub-fractions, ETA.4, ETA.8, ETA.9 and ETA.11, exhibited antimalarial activity with IC50 values at 0.035, 0.187, 0.015 and 0.017 μg/mL. Sub-fractions ETA.11 separated using preparative TLC yielded ETA.11.1 and ETA.11.2. Sub-fractions ETA.11.1 and ETA.11.2 showed antimalarial activity with IC50 values at 0.011 and 0.01 μg/mL. The TLC chromatogram of active sub-fractions showed flavonoids and phenolic. Conclusion: Crude isolates ETA.11.1 and ETA.11.2 contain flavonoid compounds and have potential antiplasmodial activity.