Isolation of two homologous triterpenes with antimalarial activities from the leaf extract of combretum zenkeri

Abstract

Combretum genus (Combretaceae) is used locally in the treatment of various diseases including malaria. Current study aimed to investigate the antiplasmodial activities of methanol extract of C. zenkeri in Plasmodium falciparum chloroquine sensitive (D10) and resistant (W2) strains and identify the bioactive principles. Repeated chromatographic separation was carried out on the chloroform fraction to afford the isolation of bioactive compounds which was characterized by application of spectroscopic techniques (ESI-MS, HR-ESIMS, 1D and 2D NMR). Antiplasmodial activities of chloroform fraction (D10; IC50= 12.57±1.57 μg/mL and W2; IC50= 12.14±0.95 μg/mL) showed more activity than the n-butanol fraction (D10; IC50= 61.98±3.25 μg/mL and W2; IC50= 61.26±8.64 μg/mL). Phytochemical investigation of the extract afforded isolation of two triterpenes with antimalarial activities. This paper identified for the first time the antimalarial principles in C. zenkeri as ursolic and oleanolic acids; which justified the local use of the plant in the treatment of malaria.