Publication: Evaluation of digestive vacuole pH in plasmodium falciparum following treatment with ρ-cymene
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Date
2026-01
Authors
Yee, Chin En
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Abstract
Malaria is a life-threatening disease caused by the Plasmodium spp., and the emergence of resistance to existing antimalarial drugs necessitates the need for alternative or complementary therapeutic agents. Essential oils are complex mixtures of bioactive compounds, the majority of which are small, lipophilic constituents that can readily interact with biological membranes and intracellular targets. ρ-cymene, a naturally occurring monoterpene found in essential oils, has been reported to possess anti-inflammatory, antioxidant, and oxidative stress-modulating properties, suggesting potential antimalarial activity. In addition to the limited research on the antimalarial activity of ρ-cymene, this study aimed to evaluate the in vitro antimalarial effect and the alteration of digestive vacuole pH induced by ρ-cymene against a chloroquine-sensitive strain of P. falciparum. Continuous parasite culture was established and synchronised prior to drug exposure. The IC50 of ρ-cymene was determined by calculating parasitaemia from microscopic examination of a Giemsa-stained thin blood smear following 48-hour drug treatment. A further investigation of the pH alteration of ρ-cymene in the digestive vacuole of P. falciparum was conducted using flow cytometry with fluorescein isothiocyanate-dextran (FITC-dextran) as the pH-ratiometric probe. The ρ-cymene exhibited promising antimalarial activity with an IC50 of 60.70 μM. Flow cytometry results revealed a significant alkalinisation of the digestive vacuole (p < 0.001) following ρ-cymene treatment at different concentrations based on its IC50 value, when compared with untreated parasites. In conclusion, this study provides preliminary evidence that ρ-cymene has in vitro antimalarial activity by potentially disrupting V-type H⁺-ATPase activity, thereby reducing proton translocation and leading to the consequent alkalisation of the digestive vacuole.