Antimalarial Activity of Some Extracts and Isolated Constituents from Morinda morindoides Leaves

Abstract

Objective: The study deals with the evaluation of the in vitro antimalarial activity of three crude extracts (ethanol and 80% methanol) from the leaves of Morinda morindoides (Baker) Milne-Redh. (Rubiaceae), that of their respective soluble fractions and isolated compounds, and that of the dichloromethane extract. It also reports the in vivo antimalarial activity of the three crude extracts and the petroleum ether soluble fraction from the ethanol extract as well as the toxicity of crude extracts in mice. Materials and methods: The ethanol, 80% methanol and dichloromethane extracts were obtained by maceration and percolation of powdered dried M. morindoides leaves. The ethanol extract was dissolved in 100 ml distilled water and extracted with petroleum ether, and then acidified with HCl 2N (pH 2-3) and successively and exhaustively treated with chloroform and isoamylic alcohol. On the other hand the 80% methanol extract was dissolved in 100 ml distilled water and successively and exhaustively extracted with chloroform, ethyl acetate and n-butanol. A series of flavonoids, anthraquinones and iridoids were isolated from the 80% methanol extract. All dried samples were tested for their potential in vitro antiplasmodial activity against Congolese the chloroquine-sensitive or the chloroquine-sensitive NF54/64, clone A19 strains of Plasmodium falciparum according to the case. The three extracts and one soluble fraction were tested in vivo against Plasmodium berghei berghei in a classical 4-suppressive test. Results: The petroleum ether, isoamylic alcohol and chloroform soluble fractions from the partition of ethanol extract showed an in vitro antiplasmodial activity against Congolese the chloroquine-sensitive strain of P. falciparum with IC₅₀ values of 1.8 ± 0.2, 15.3 ± 3.6 and 8.8 ± 2.5 μg/ml respectively. Only the chloroform soluble fraction from the partition of the 80% methanol exhibited good antiplasmodial activity with IC₅₀ value of 8.3 ± 1.6 μg/ml against the chloroquinesensitive NF54/64, clone A1A9 strain of P. falciparum. Among isolated compounds, quercetin exhibited good antiplasmodial activity with IC₅₀ value of 5.5. ± 1.8 μg/ml, alizarin and chrysarin showed a moderate activity with IC₅₀ ranging from 14 to 26 μg/ml. In vivo test, at a daily oral dose of 200 mg/kg, ethanol, 80% methanol and dichloromethane extracts, and the petroleum ether soluble fraction produced 33%, 54% and 73%, and 75% chemosuppression respectively. Conclusion: These results may partly justify and support the traditional use of Morinda morinoides leaves for the treatment of malaria.