In vitro screening of ten Combretaceae plants for antimalarial activities applying the inhibition of beta-hematin formation

Abstract

The identification of novel molecules for the development of more effective and safe treatments to fight malaria is urgently needed. Medicinal plants are one of the main opportunities in the discovery of such new molecules. Combretaceae is a family members of which have been reported with broad spectrum of bioactivities against different diseases including malaria. The aim of this study was to screen a number Combretaceae plants, selected based on the use in ethnomedicine, for antimalarial activity. Methanolic and acetone extracts of leaves of ten different Combretaceae were screened by applying the inhibition of β-hematin synthesis, a simple and robust colorimetric assay. The analysis was conducted using a 96-well UV-vis plate reader and the absorbance was read at 405 nm. The IC₅₀ was calculated by analyzing the dose-response data using Graphpad Prism^® (6.0). Preliminary results showed that eight plant extracts at 25mg/mL demonstrated appreciable activity by inhibiting the formation of hemozoin. The best inhibitory concentration (IC₅₀ 2.58 ± 0.447 mg/mL) was observed in Terminalia ivorensis methanol extract (TIM) which was comparable with chloroquine standard drug (IC₅₀ 0.55 ± 0.179 mg/mL). Moreover, the Terminalia ivorensis methanol extract showed statistically significant activity (P<0.05) at the different concentrations used, comparable to chloroquine. Activities studies of the investigated plants confirm the ethnomedicinal use of Terminalia ivorensis in the treatment of malaria. A bioassay-guided fractionation of the leaf extract of the T. ivorensis is ongoing.

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Keywords: Combretaceae, antimalarial, β-hematin inhibition, Terminalia ivorensis