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Vernonia amygdalina Del. is a conventional herbal drug in Congolese traditional medicine and is widely used for the treatment of malaria.The aim of this work is to evaluate its efficacy and safety and the potential antimalarial activity of another species originating from Madagascar. Standard bioassay models based on in vitro and in vivo systems that enable bioactivity screening of traditionally used medicinal plants were used. In particular, hydro-alcoholic extracts of two Vernonia species growing in two different geographical regions(Congo DR and Madagascar) were evaluated for the inhibitory effects on two malaria parasites strains and cytotoxicity towards leukaemia P-388 cell lines. Results indicate that, V. amygdalina possess a very good in vitro and in vivo activities and a good therapeutic index than V. cinerea subsp vialis endemic to Madagascar, thus validate scientifically the efficacy and safety of Vernonia amygdalina in the traditional treatment of malaria in Congo DR. Using chemotaxonomic approach, we also detected moderate antiplasmodial activities in V. cinerea subsp vialis a plant species not previously reported as antimalarial in the traditional medicine knowlegde of Madagascar. It would be concluded that despite the long spatial isolation of Madagascar and allopatric speciation, Vernonia ecotype as V. cinerea subsp vialis has preserved the antiplasmodial properties. This approach gives the possibility to select plant species of the same genus from different geographical regions in order to increase the chance of discovering new biologically active plants.

Anthocyanin crude extracts and fractions of Annona senegalensis leaves were screened for their antisickling properties using a validated in vitro bioassay model of sickle cell anaemia. Preparative thin layer chromatography of acetylated anthocyanin crude extracts carried out with chloroform as solvent provided two active fractions named Ac 1 and Ac 2 . Fraction Ac 2 was quantitatively isolated and submitted to physicochemical investigations. Thermo-degradation kinetics of the above fraction Ac 2 at 80 °C and 100 °C revealed first order reaction with the rate constants k (s -1 ) of 8.10 10 -4 and 11.0 10 -4 , respectively. Anthocyanin crude extracts and the separated fractions showed in vitro antisickling activity. This activity justifies the use of this plant by congolese traditional healers; thus anthocyanins could be the major active principles. However, these natural pigments are unstable towards UV-vis light irradiations and heat. The conservation of this plant should then be performed in the absence of heat and/or light.

Hydro-alcoholic extracts of some plant species growing in two different geographical regions (Democratic Republic of Congo and Madagascar) were evaluated for their inhibitory effects on two malaria parasites strains (P. falciparum FcM29 & P. yoelii subsp nigeriensis) and cytotoxicity towards leukaemia P-388 cell lines. Results indicate that, the antiplasmodial activity of tested plants varied geographically. Plants growing in continent ecosystem are more active in vitro while their ecological equivalence inhabiting island ecosystems are more active in vivo. It would be conclude that, the development of phytomedicines from plants of different geographical regions selected by bioguided fractionation would allow the populations to reduce the health care cost. The chemotaxonomic approach has also permitted us to detect moderate antiplasmodial activities in Neobegua mahafaliensis, a plant species not previously reported as antimalarial in the traditional medicine knowlegde of Madagascar. The use of a pharmacological property such as the antimalarial activity, in this study, in order to establish genetic filiations between the plants species is an original approach.