Isolation and in vitro antimalarial activity of hexane extract from Thai Picrasma javanica B1 stembark

The in vitro antimalarial activities against Plasmodium falciparum K1 of four extracts from the stembark of Picrasma javanica B1; ie water, methanol, chloroform and hexane extracts were studied using a modification of the [3H]hypoxanthine incorporation method. It was found that the hexane extract showed in vitro antimalarial activity with IC50 of 3.3 microg/ml. The extract was further fractionated using quick column chromatography, resulting in ten fractions. Fraction V was the most effective against P. falciparum K1 with IC50 of 4.4 microg/ml. Further isolation of fraction V using a column chromatographic technique provided six fractions. According to 1H- and 13C-NMR spectra, it could be concluded that the major compound in fraction V-3 was beta-sitosterol. Unfortunately, the antimalarial activity of beta-sitosterol could not be determined because of its low solubility in DMSO. However, fractions V-2 and V-4 still showed in vitro antimalarial activities with IC50 of 2.8 and 3.4 microg/ml, respectively. The further fractionation of these two active fractions could lead to promising candidates as antimalarial agents.