Antiplasmodial Activity of Aidia genipiflora and its Oleanane Triterpenoid, Oleanonic Acid

Background

The emergence of resistance to frontline antimalarial therapies continues to undermine global malaria control efforts, especially in sub-Saharan Africa. The search for novel scaffolds from endemic medicinal plants remains a crucial strategy.

Objectives

This study evaluated the antiplasmodial activity of Aidia genipiflora stem bark extract and its pentacyclic triterpenoid, oleanonic acid.

Material and Methods

The in vitro antiplasmodial activity of the methanolic extract and oleanonic acid was determined against chloroquine-resistant Plasmodium falciparum Dd2 were assessed using the SYBR Green I fluorescence assay. In vivo efficacy was investigated using the Plasmodium berghei ANKA in mice. Cytotoxicity of oleanonic acid was tested on human Red Blood Cells (RBCs) and HepG2 liver cells. Dihydroartemisinin (0.5-8 mg/kg) and saline served as positive and negative controls, respectively.

Results

The extract and oleanonic acid exhibited notable in vitro activity with IC₅₀ values of 6.28 µg/mL and 8.67 µg/mL, respectively. Oleanonic acid was non-toxic to RBCs (IC₅₀>100 µg/mL) but showed moderate toxicity to HepG2 cells (IC₅₀= 5.01 µg/mL), with selectivity indices of >11.53 and 0.59, respectively. In vivo, both extract and compound significantly (p<0.05) suppressed parasitaemia, with ED₅₀ values of 14.76 mg/kg for the compound and 3.96 mg/kg for dihydroartemisinin.

Conclusion

While oleanonic acid has been previously reported with antiplasmodial effects, this study provides the first evidence of its in vivo efficacy when isolated from A. genipiflora, highlighting this species as a novel source of antiplasmodial triterpenoids. The findings justify further mechanistic, pharmacokinetic, and structure-activity studies to optimize safety and efficacy.