In vitro antiplasmodial activity-directed investigation and UPLC-MS fingerprint of promising extracts and fractions from Terminalia ivorensis A. Chev. and Terminalia brownii Fresen.

ETHNOPHARMACOLOGICAL SIGNIFICANCE: Medicinal plants from the Terminalia genus are widely used as remedies against many infectious diseases, including malaria. As such, Terminalia ivorensis A. Chev. and Terminalia brownii Fresen. are famous due to their usefulness in traditional medicines to treat malaria and yellow fever. However, further information is needed on the extent of anti-Plasmodium potency of extracts and fractions from these plants and their phytochemical profile.

AIM OF THE STUDY: This study was designed to investigate the in vitro antiplasmodial activity and to determine the chemical profile of promising extracts and fractions from T. ivorensis and T. brownii stem bark.

MATERIALS AND METHODS: Crude aqueous, ethanolic, methanolic, hydroethanolic and ethyl acetate extracts were prepared by maceration from the stem barks of T. brownii and T. ivorensis. They were subsequently tested against chloroquine-sensitive (Pf3D7) and multidrug-resistant (PfDd2) strains of P. falciparum using the parasite lactate dehydrogenase (PfLDH) assay. Extracts showing very good activity on both plasmodial strains were further fractionated using column chromatography guided by evidence of antiplasmodial activity. All bioactive extracts and fractions were screened for their cytotoxicity on Vero and Raw cell lines using the resazurin-based assay and on erythrocytes using the hemolysis assay. The phytochemical profiles of selected potent extracts and fractions were determined by UPLC-QTOF-MS analysis.

RESULTS: Of the ten extracts obtained from both plant species, nine showed inhibitory activity against both P. falciparum strains (Pf3D7 and PfDd2), with median inhibitory concentration (IC50) values ranging from 0.13 μg/ml to 10.59 μg/ml. Interestingly, the aqueous extract of T. ivorensis (TiW) and methanolic extract of T. brownii (TbM) displayed higher antiplasmodial activities against both strains (IC50 0.13-1.43 μg/ml) and high selectivity indices (SI > 100). Their fractionation led to two fractions from T. ivorensis and two from T. brownii that showed very promising antiplasmodial activity (IC50 0.15-1.73 μg/mL) and SI greater than 100. The hemolytic assay confirmed the safety of crude extracts and fractions on erythrocytes. UPLC-MS-based phytochemical analysis of the crude aqueous extract of T. ivorensis showed the presence of ellagic acid (1) and leucodelphidin (2), while analysis of the crude methanol extract of T. brownii showed the presence of ellagic acid (1), leucodelphinidin (2), papyriogenin D (3), dihydroactinidiolide (4) and miltiodiol (5).

CONCLUSIONS: The extracts and fractions from T. ivorensis and T. brownii showed very good antiplasmodial activity, thus supporting the traditional use of the two plants in the treatment of malaria. Chemical profiling of the extracts and fractions led to the identification of chemical markers and the known antimalarial compound ellagic acid. Further isolation and testing of other pure compounds from the active fractions could lead to the identification of potent antiplasmodial compounds.