Bioassay guided fractionation of antimalarial extracts from plants used in traditional medicine

There is a continuing need to develop new and more effective drugs against malaria because of increasing instances of the resistance of certain parasite strains to current drugs, including artemisinin [1, 2]. Plants have provided some of the best antimalarial drugs, such as Artemisia annua which is the source of artemisinin. This drug was originally discovered based on traditional Chinese medicine [3], indicating the utility of searching for antimalarial natural products from plants used in traditional medicine. Plants of the Anthocleista genus have found use as antimalarial agents [4], while plants of the Dombeya genus have been used for their anti-inflammatory and antibacterial activities [5]. A bioassay-guided strategy, using the drug-resistant Dd2 strain of Plasmodium falciparum as the bioassay, was thus adopted to fractionate the methanolic extracts of Dombeya oblongifolia (IC₅₀ < 1.25µg/mL) and Anthocleista madgascariensis (IC₅₀ < 1.25µg/mL). Compounds 1-4 were isolated from bioactive fractions of D. oblongifolia, while compounds 5-8 were isolated from bioactive fractions of A. madgascariensis. The structures of the isolated compounds were determined using IR, UV, mass spectrometry, and 1D and 2D NMR techniques.

Acknowledgements: Support from the U.S. National Center for Complementary and Integrative Health (NCCIH) under award 1 R01 AT008088 is gratefully acknowledged.

Keywords: Bioassay guided fractionation, Antimalarial activity, 1D- and 2D-NMR.

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