Abstract
The resistance of malaria parasites towards the current antimalarial therapies continues
to fuel the search for new antimalarial drugs, preferably from natural sources. This study
aimed to investigate the potential of the dichloromethane extract of Acanthospermum australe
to inhibit Plasmodium falciparum heat shock protein 70-1 (Pf Hsp70-1). The plasmodium
lactate dehydrogenase (pLDH) assay was used to determine the antiplasmodial activity of
the crude extract against the chloroquine-sensitive P. falciparum strain 3D7. The inhibitory
effect of the plant extract on the chaperone activity of P. falciparum heat shock protein
70-1 (Pf Hsp70-1) was determined using the ATPase, thermally induced luciferase and
malate dehydrogenase (MDH) assays. The extract showed a significantly high activity
against P. falciparum strain 3D7 with an IC50 value of 1.3 μg/mL. A decrease in thermally
induced aggregation of MDH and luciferase was observed when each of the proteins was
incubated with Pf Hsp70-1 only. However, an increased protein aggregation was observed
when the proteins were incubated with Pf Hsp70-1 in the presence of the plant extract. The
extract also exhibited inhibitory activity on the ATPase activity of Pf Hsp70-1. The results
obtained from this study suggest that A. australe extract contains compounds that could
target malaria parasite Hsp70 functions.