The antiplasmodial activity of the crude extracts of thirty plant species collected from Sabah was evaluated using chloroquine-sensitive strain (D10) and chloroquine-resistant strain (Gombak A) of Plasmodium falciparum. Significant activities were observed for the bark extract of Polyalthia insignis (IC50 3.89 and 11.89 mg/ml against Gombak A and D10, respectively), the leaf extracts of Kopsia dasyrachis (4.62 mg/ml against Gombak A) and Litsea elliptibacea (IC50 8.88 mg/ml against Gombak A), as well as the leaf and bark extracts of Neouvaria acuminatissima (IC50 6.90-10.08 and 0.69 mg/ml against Gombak A and D10, respectively), and the bark extract of Polyalthia microtus(IC50 9.0 and 12.12 mg/ml against Gombak A and D10, respectively).
Seven Malaysian medicinal plants were screened for their antiplasmodial activities in vitro. These plants were selected based on their traditional claims for treatment or to relieve fever. The plant extracts were obtained from Forest Research Institute Malaysia (FRIM). The antiplasmodial activities were carried out using the pLDH assay to Plasmodium falciparum D10 strain (sensitive strain) while the cytotoxic activities were carried out towards Madin- Darby bovine kidney (MDBK) cells using MTT assay. The concentration of extracts used for both screening assays were from the highest concentration 64 microg/ml, two fold dilution to the lowest concentration 0.03 microg/ml. Goniothalamus macrophyllus (stem extract) showed more than 60% growth inhibition while Goniothalamus scortechinii root and stem extract showed a 90% and more than 80% growth inhibition at the last concentration tested, 0.03 microg/ml. The G. scortechini (leaves extract) showed an IC50 (50% growth inhibition) at 8.53 microg/ml, Ardisia crispa (leaves extract) demonstrated an IC50 at 5.90 +/- 0.14 microg/ml while Croton argyratus (leaves extract) showed a percentage inhibition of more than 60% at the tested concentration. Blumea balsamifera root and stem showed an IC50 at 26.25 +/- 2.47 microg/ml and 7.75 +/- 0.35 microg/ ml respectively. Agathis borneensis (leaves extract) demonstrated a 50% growth inhibition at 11.00 +/- 1.41 microg/ml. The study gives preliminary scientific evidence of these plant extracts in line with their traditional claims.