Abstract:
Ethnopharmacological relevance: Pappea capensis (Sapindaceae), traditionally used by VhaVenda people in South Africa to treat malaria, was evaluated for antiplasmodial activity and cytotoxicity. Materials and methods: Ground twigs were extracted using dichloromethane (DCM): 50% methanol (MeOH) (1:1, v/v), separated and dried under vacuum to yield DCM (I) and aqueous (II) extracts. The extract I was further partitioned using DCM: MeOH (1:1, v/v), separated and concentrated under vacuum to yield dichloromethane (III) and methanol (IV) crude extracts. A water-based decoction (V) was also prepared to establish the clinical relevance of the preparation administered by indigenous people. In vitro, antiplasmodial tests using the chloroquine-sensitive strain of Plasmodium falciparum (NF54) were conducted for all crude extracts (I – V). Cytotoxicity screening was performed on mammalian L-6 rat skeletal myoblast cells, and the plant samples' selectivity indices (SI) were computed. The crude extracts were then subjected to 1H NMR spectroscopy and GC-MS analysis to identify the major classes of compounds present in the crude extracts. Results and discussion: From the assayed crude extracts, I (IC50 = 2.93 μg /ml; SI = 14), III (IC50 = 2.59 μg /ml; SI = 21) and IV (IC50 = 3.56 μg /ml; SI = 13) demonstrated the best antiplasmodial activity and selectivity. Of all assayed fractions, only N (0.6 μg /ml; SI=91), D (0.85 μg /ml; SI=37) and E (0.91 μg /ml; SI =30) depicted the best antiplasmodial activity and selectivity. The 1H NMR analysis of crude extracts tentatively identified the prominent class of constituents to be aliphatic based. When subjected to GC-MS analysis, lupin-3-one, lupeol acetate, α-amyrin, and β-amyrin phytoconstituents were observed in the crude extracts. These identified compounds are (aliphatic-based constituents) with established antiplasmodial activity, and the observed antiplasmodial activity of P. capensis can be attributed to them. The results obtained from the GC-MS and 1H NMR data can be correlated with the observed antiplasmodial biological activity of P. capensis crude extracts. Conclusion: The study validates the ethnomedicinal use of P. capensis for malaria treatment. It demonstrated the potential of discovering novel antiplasmodial constituents that could serve as drug hits through dereplication approaches were known compounds with established antimalarial activity can be bypassed to focus on the unknown.
