Chemotherapeutic treatment of malaria has evolved in the last ten years due to the spread of multi-resistant Plasmodium falciparum strains. The World Health Organization (WHO) currently promotes artemisinin-based combination therapy (ACT) as the reference medicine for health care management of uncomplicated falciparum malaria in order to reduce the risk of resistance . However, some signs of resistance to artemisinin have recently been detected in Asia [2–4], representing an enormous threat for the control of the disease. The discovery of new anti-malarial drugs is urgently needed and natural products could play an important role in this new challenge.
The plant kingdom has been and remains a good source of pharmacologically active compounds and especially anti-plasmodial agents, as attested by quinine, isolated from Cinchona sp., and artemisinin extracted from Artemisia annua. Besides these well-known examples, various new anti-plasmodial natural compounds are frequently being discovered, as reviewed by several authors in recent years [5–9].
WHO estimates that up to 80% of the world's population relies on traditional medicinal products for some aspects of primary health care [10, 11]. Many people living in developing countries do not have access to modern therapeutics, such as ACT, to treat malaria because of financial, socio-economical, geographical and/or cultural reasons, and they use plants, often in combination, for the health care management of malaria.
The search for new anti-malarial natural products, following an ethnopharmacological strategy (based on traditional knowledge of plants), has led to interesting results, as reviewed and commented on by Willcox et al.[12, 13].
Moreover, there is now evidence that some whole plant extracts can be more active than single compounds, as a result of synergy and positive interactions between different constituents in the extracts, compared to a single product [14, 15].
In this context, the pharmacological and phytochemical study of plants from traditional pharmacopoeias can be of interest, not only in discovering new anti-malarial “lead compounds”, but also in valorizing local vegetal species whose efficacy and safety has been demonstrated in laboratory and clinical investigations .
Better knowledge of plants from traditional pharmacopoeias and local valorization of traditional remedies in improved traditional medicine (ITM) could lead to effective, standardized, available and affordable therapeutics for the management of malaria by local populations, when modern drugs are unavailable .
Validated anti-malarial phytomedicines formulated from traditional medicines have been reported in recent years. Some are government approved in different countries, e g, Argemone mexicana in Mali, whose anti-malarial activity has been confirmed in clinical trials , and “Saye” in Burkina Faso, a combination of three plants, used for several years as a curative anti-malarial and recently studied for its benefits in the prophylaxis of malaria .
In a previous study dealing with the screening of several plants used in Burkina Faso in the traditional treatment of malaria, Dicoma tomentosa was selected for its promising anti-plasmodial activity .
Dicoma tomentosa is a plant of the Asteraceae family growing in Asia and tropical Africa. It is an uncommon species, mainly found in the Sahelo-Sudanian area. Called “Gômtigdà” in the local language (Mooré), the decoction of the whole plant is traditionally used in Burkina Faso to treat malaria in adults and children, particularly malaria with spleen and liver “inflammation” . The plant is also known for its benefits against cough and in postnatal care to “wash the belly”, but it is not recommended for pregnant women because it is known to cause abortion.
The plant has been described as containing several sesquiterpene lactones [22–24], triterpenes and sterols [25, 26] as well as flavonoids [27–30], but has never been studied for any biological or pharmacological properties.
The aim of the present study was to further evaluate the anti-plasmodial potential of D. tomentosa using in vitro and in vivo models. In vitro cytotoxic and haemolytic properties were also studied in order to check the selectivity of the plant and thereby to appreciate its safety of use.
Finally, a bioguided fractionation was undertaken to complete the study. This phytochemical analysis led to the isolation and identification of the major active compound.