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Antimicrobial Agents and Chemotherapy, January 2005, p. 264-268, Vol. 49, No. 1
0066-4804/05/$08.00+0     doi:10.1128/AAC.49.1.264-268.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Effects of Root Extracts of Fagara zanthoxyloides on the In Vitro Growth and Stage Distribution of Plasmodium falciparum

Department of Microbiology,¹ Department of Medicine,² Center for Sickle Cell Disease, Howard University College of Medicine, Washington, D.C.,³ Biocal, Inc., San Diego, California⁴

Received 26 April 2004/ Returned for modification 21 June 2004/ Accepted 15 September 2004

The development of resistance by Plasmodium falciparum to conventional drugs poses a threat to malaria control. There is therefore a need to find new, effective, and affordable remedies for malaria, including those derived from plants. This study demonstrates that crude, reverse-phase high-pressure liquid chromatography (RP-HPLC)-semipurified, and RP-HPLC-purified root extracts of Fagara zanthoxyloides inhibit the growth of P. falciparum in vitro, with 50% inhibitory concentrations (IC₅₀s) of 4.90, 1.00, and 0.13 µg/ml, respectively. Roots of F. zanthoxyloides, known as chewing sticks, are widely used for tooth cleaning in West Africa. Microscopic examination of Giemsa-stained slides showed a virtual absence of schizonts in ring-stage synchronized cultures treated with crude extracts at concentrations of 30 to 60 µg/ml during 36 to 48 h of incubation. These observations suggest that the active constituent in the extract may be cytotoxic for P. falciparum trophozoites, thereby inhibiting their development to the schizont stage. A pure bioreactive fraction was subsequently obtained from the chromatographic separations. When this fraction was mixed with pure fagaronine, the mixture coeluted as a single peak on the analytical RP-HPLC column, suggesting that fagaronine may be the active antimalarial constituent of Fagara root extracts. Additional experiments showed that fagaronine also inhibited P. falciparum growth, with an IC₅₀ of 0.018 µg/ml. The results of this study suggest that the antimalarial activity of fagaronine deserves further investigation.