Chem. Pharm. Bull. 55(3) 464—467 (2007)

diseases in the world. It constitutes a public health problem in more than 90 countries, inhabited by about 40% of the world’s population. The World Health Organisation estimates that there are 300—500 million malaria cases annually, causing 2—3 million deaths, mostly in children under five years old. Africa accounts for over 90% of malaria mortality. Malaria also has significant economic impacts in endemic countries, costing Africa $ 12 billon in lost gross domestic product every year and consuming 40% of all public health spending. Most countries where Plasmodium falciparum malaria, the most severe and dangerous form of this disease, is endemic face significant parasite resistance to frequently used antimalarial drugs, in particular chloroquine and antifolates. Furthermore, resistance to artemisinins, which are the most promising new antimalarials, has been induced in rodent malarial models and identified rarely in clinical isolates. If resistance to artemisinins emerges, no drug will be available to reliably offer protection against malaria in all parts in the world and the efficacy of new artemisinin-based combination therapies (ACTs), which are highly effective, but expensive, will be jeopardized. For these reasons, new effective and affordable antimalarials are badly needed. In this regard research on traditional medicinal plants for their antimalarial constituents is important, to facilitate utilization of available botanical resources and to provide potentially active lead anti-plasmodial compounds, perhaps with new mechanisms of action. In Africa, the use of indigenous plants still plays an important role in the treatment of malaria. Some anthrone derivatives from plant sources have demonstrated interesting anti-plasmodial activity. They are also naturally occurring competive inhibitors of adenosine– triphosphate-citrate-lyase. Plants of the Hypericaceae family are well known to produce bioactive anthraquinones and anthrones. They are distributed in tropical and sub-tropical regions. Harungana madagascariensis, a plant from this family, is used for various medicinal purposes in Africa. Leaf extract of this plant exhibited antibacterial activity. In the West province of Cameroon, the roots and bark are used by traditional healers to treat malaria. Various phenolic compounds have been isolated from this plant, among them anthraquinones, xanthones, biflavonoids, coumarins and anthrone derivatives. These compounds have demonstrated a wide range of biological activities. Although some phytochemical and pharmacological studies have been carried out on H. madagascariensis, no investigation has been reported, to the best of our knowledge, on the anti-plasmodial activity of its constituents. In our continuing interest in new anti-plasmodial metabolites from plant sources, we investigated the MeOH–CH2Cl2 (1 : 1) root bark extract of this plant which showed anti-plasmodial activity (IC50 25.12 mg/ml) against W2 strain P. falciparum. In this paper, we report the isolation and structure elucidation of a new anthrone derivative and the anti-plasmodial activity of the isolated compounds. The air dried root bark of Harungana madagascariensis was extracted at room temperature with a mixture of MeOH–CH2Cl2 (1 : 1). The extract was concentrated to dryness under vacuum and the residue subjected to repeated column chromatography to yield compound (1) along with the known feruginin A (2), harunganin (3), harunganol A (4), harunganol B (5), friedelan-3-one (6) and betulinic acid (7). Compound (1) was obtained as an orange powder, mp 178— 179 °C. It gave positive ferric chloride and Gibbs tests, indicating its phenolic nature. The molecular formula C30H36O5 was deduced from HR-ESI-TOF mass spectrometry which showed a pseudomolecular ion peak at m/z 477.6089, corresponding to 15 degrees of unsaturation. The IR spectrum exhibited strong absorption bands due to conjugated carbonyl (1615 cm ) and chelated hydroxyl group(s) (3261 cm ). The UV absorptions at lmax 208, 236, 263, 388 nm, combined with IR spectral data, were suggestive of an anthranoid 464 Vol. 55, No. 3