No document available.
Abstract :
[en] Malaria remains a major concern for health organizations around the world. In 2017, the World Health Organization reported more than 219 million cases and 435.000 deaths. With 87 countries affected, more than 800 million people are at risk of infection. The emergence and transmission of resistances to most antimalarial drugs are a real worry. Thus, the need for new therapeutic candidates represents an absolute necessity [1]. In more recent years, animal venoms and secretions have sparked a growing interest for scientists. In fact, toad venoms constitute a rich source of molecules, mainly bufadienolides, with many potential therapeutic activities [2].
The objective of this on-going project is to develop a bio-guided fractionation process and the subsequent discovery of new drug candidates against malaria from toad venom.
Raw extract characterization: Multiple Bufo species will be considered during this work. Up to now, two species have been studied: Rhinella marina and Bufo bufo. The extraction process from the air-dried gland secretions of the Bufo toads consists of an ultrasonication-assisted solvent extraction. Two solvents have been tested: methanol and acetonitrile. The venom composition is subject to variabilities between batches depending on the animal's habitat and its diet. After each extraction, the raw extracts are analyzed by TLC and LC-MS to have an overview of the compounds present in the sample. Fractionation process: During this step, flash chromatography is considered as a first approach to obtain rough fractions that will also be analyzed by TLC and LC-MS and then biologically studied. Flash chromatography offers a fast and simple separation process that can be applied to complex natural products. In the first fractionation round, 3 to 4 fractions are obtained. The following step will consist in producing subfractions of the fractions displaying interesting therapeutic properties. For this purpose, further preparative techniques will be considered such as flash chromatography and semi-preparative HPLC. Biological activity: Each raw extract and the subsequently obtained fractions are tested for their antiplasmodial activity (3D7 and W2 strains) using the pLDH assay and the microscopic evaluation. Their cytotoxicities are also assessed on a panel of human cell lines. A parallel project aims to evaluate the effect of the hereabove mentioned extracts and fractions on several human melanoma cell lines that have developed resistance to targeted therapies. The samples that display antiplasmodial activities and/or cytotoxic activities against melanoma cells will be further analyzed (LC-MS) and structurally characterized by NMR analysis (1H-NMR, 13C-NMR, COSY).
