Approche phylogénétique

Projet en cours

Algues marines anti-Apicomplexes

Les parasites apicomplexes (Plasmodium, Toxoplasma …) sont issus d’une endosymbiose secondaire entre une cellule eucaryote ancestrale et une algue rouge. De cette endosymbiose, ceux-ci ont hérité d’un chloroplaste vestigial d’origine algale (Wilson et Williamson, 1997). L’analyse de la relation phylogénétique qui lie certaines macro-algues à Plasmodium (Baumeister et al., 2010 ; Biot et al., 2012) montre que ceux-ci partagent plusieurs voies biochimiques essentielles à la survie de Plasmodium (Marechal et Cesbrun-Delaw, 2001). Le laboratoire s’appuie sur ce lien phylogénétique pour rechercher dans les algues des modulateurs capables d’interférer avec ces voies communes chez le parasite.

Eleganolone, a Diterpene from the French Marine Alga Bifurcaria bifurcata Inhibits Growth of the Human Pathogens Trypanosoma brucei and Plasmodium falciparum

Marine Drugs, 2013, 11(3):599-610

Abstract : Organic extracts of 20 species of French seaweed have been screened against Trypanosoma brucei rhodesiense trypomastigotes, the parasite responsible for sleeping sickness. These extracts have previously shown potent antiprotozoal activities in vitro against Plasmodium falciparum and Leishmania donovani. The selectivity of the extracts was also evaluated by testing cytotoxicity on a mammalian L6 cell line. The ethyl acetate extract of the brown seaweed, Bifurcaria bifurcata, showed strong trypanocidal activity with a mild selectivity index (IC50 = 0.53 µg/mL; selectivity index (SI) = 11.6). Bio-guided fractionation led to the isolation of eleganolone, the main diterpenoid isolated from this species. Eleganolone contributes only mildly to the trypanocidal activity of the ethyl acetate extract (IC50 = 45.0 µM, SI = 4.0). However, a selective activity against P. falciparum erythrocytic stages in vitro has been highlighted (IC50 = 7.9 µM, SI = 21.6).

Graphical abstract

Antiprotozoal activities of organic extracts from French marine seaweeds

Marine Drugs 2011, 9:922-933

Abstract : Abstract: Marine macrophytes contain a variety of biologically active compounds, some reported to have antiprotozoal activity in vitro. As a part of a screening program to search for new natural antiprotozoals, we screened hydroalcoholic and ethyl acetate extracts of 20 species of seaweeds from three phyla (Rhodophyta, Heterokontophyta and Chlorophyta), sampled along the Normandy (France) coast. We tested them in vitro against the protozoa responsible for three major endemic parasitic diseases: Plasmodium falciparum, Leishmania donovani and Trypanosoma cruzi. The selectivity of the extracts was also evaluated by testing on a mammalian cell line (L6 cells). Ethyl acetate extracts were more active than hydroalcoholic ones. Activity against T. cruzi and L. donovani was non-existent to average, but almost half the extracts showed good activity against P. falciparum. The ethyl acetate extract of Mastocarpus stellatus showed the best antiplasmodial activity as well as the best selectivity index (IC50 = 2.8 µg/mL; SI > 30). Interestingly, a red algae species, which shares phylogenetic origins with P. falciparum, showed the best antiplasmodial activity. This study is the first to report comparative antiprotozoal activity of French marine algae. Some of the species studied here have not previously been biologically evaluated.

X-ray structure of floridoside isolated from the marine red algae Dilsea carnosa

Carbohydrate Research, 2008, 343(15):2697-2698

Abstract : The natural floridoside (2-O-alpha-d-galactopyranosylglycerol) was isolated from Dilsea carnosa, and its structure has been determined by single-crystal X-ray diffraction analysis. The solved structure is in agreement with the previously solved crystal structure of floridoside [Simon-Colin, C.; Michaud, F.; Léger, J.-M.; Deslandes E. Carbohydr. Res.2003, 338, 2413-2416] and demonstrates for the first time the presence of floridoside in the red algae Dilsea carnosa.