Étude écologique et chimique de deux algues introduites sur les côtes bretonnes, Grateloupia turuturu Yamada et Sargassum muticum (Yendo) Fensholt (nouvelles ressources biologiques de composés à activité antifouling)

Les deux algues invasives Grateloupia turuturu et Sargassum muticum présentes sur les côtes bretonnes ont été choisies comme modèles de cette étude. Les objectifs étant i) de comprendre à travers l étude de la biologie des populations les stratégies d adaptation mises en place par ces algues introduites lors de la colonisation de nouveaux habitats, ii) de mettre en évidence une éventuelle stratégie de défense chimique chez ces deux algues, basée notamment sur la production de composés antifouling, et enfin iii) de tenter d isoler les métabolites responsables de cette activité antifouling. Ainsi une étude pluridisciplinaire a été entreprise incluant un suivi écologique de Grateloupia turuturu et Sargassum muticum sur trois sites du littoral breton, un screening de l activité antifouling d extraits réalisés à partir des deux espèces d algues, et un travail mené en chimie visant à isoler et à identifier les composés présents dans les extraits actifs. Les résultats de cette étude contribuent à une meilleure connaissance de la biologie des populations de G. turuturu et S. muticum, et ont mis en évidence l impact des paramètres environnementaux sur les variables mesurées chez les deux espèces d algues. L extrait dichlorométhane de G. turuturu et l extrait chloroformique de S. muticum se sont révélés les plus actifs lors des tests antifouling. La purification de ces extraits a abouti à l isolement du cholesteryl formate chez G. turuturu et à l identification d hydrocarbures, d acides gras libres et de galactoglycérolipides chez S. muticum. Toutes ces molécules présentent une activité contre diverses souches de bactéries responsables du microfouling.The invasive algae Grateloupia turuturu and Sargassum muticum were chosen as models of this study. The aims of this work were i) to understand the population biology of G. turuturu and S. muticum and their adaptation strategies in novel habitats, ii) to determinate if their adaptation strategies were related to the development of a chemical defence based on antifouling compounds synthesis, iii) to characterize metabolites involved in this chemical defence and produced by the two algae. lien, a pluridisciplinary study was carried out including an ecological survey of the two invasive algae at three field sites selected along the coast of French Brittany, a screening of the antifouling activity of extracts from G. turuturu and £ muticum, and a chemical work in order to isolate and identify compounds present in the active extracts. Results allow us to better understand the population biology of G. turuturu and S. muticum and to higlight the impact of environmental parameters on variables studied in both species. Antifouling tests highlighted the dichloromethane extract from G. turuturu and the chloroform extract from S. muticum as the most actives. The chemical work led to the isolation of cholesteryl formate from G. turuturu and to the identification of hydrocarbons, free fatty acids and galactoglycerolipids from S. muticum. All these compounds showed antifouling activities against several strains of bacteria implicated in microfouling.BREST-BU Droit-Sciences-Sports (290192103) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF

Douleur aiguë de l'enfant traumatisé et utilisation de la morphine en titration (étude prospective aux urgences pédiatriques du CHU de Brest)

BREST-BU Médecine-Odontologie (290192102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Anti-microfouling activities in extracts of two invasive algae: Grateloupia turuturu and Sargassum muticum

International audienceMarine macroalgae are particularly prone to epiphytism. The colonisation of their surface may lead to severe perturbations and sometimes to the death of the host. To protect themselves against settling and/or competing organisms, many algae have developed defences against fouling by producing a wide variety of chemically active metabolites. The goal of this study was to investigate potential anti-microfouling activities of two introduced algal species from the Brittany coast (France), Sargassum muticum (Phaeophyceae) and Grateloupia turuturu (Rhodophyceae). Thus, a complete study of the antimicrobial activities of extracts (aqueous, acetone, chloroform, dichloromethane, diethyl-ether, ethyl acetate, ethanol 96°, hexane and methanol) from S. muticum and G. turuturu against marine fouling bacteria (5 strains), fungi (5 strains) and biofilm-associated microphytobenthic strains (5) were performed. The most active extract of G. turuturu was the dichloromethane fraction, while the chloroform extract from S. muticum showed some good results. Our data suggest that these macroalgae can provide useful compounds or templates for industrial anti-microfouling applications

Anti-microfouling activity of lipidic metabolites from the invasive brown alga Sargassum muticum (Yendo) Fensholt

International audienceThe purification of the chloroform extract from the brown invasive macroalga Sargassum muticum, through a series of chromatographic separations, yielded 12 fractions that were tested against strains of bacteria, microalgae, and fungi involved in marine biofilm formation. The chemical composition of four (a, c, g, and k) out of the six fractions that exhibited anti-microfouling activity was investigated. Fraction a contained saturated and unsaturated linear hydrocarbons (C12-C27). Arachidonic acid was identified as the major metabolite in fraction c whereas fraction g contained mainly palmitic, linolenic, and palmitoleic acids. Fraction k was submitted to further purification yielding the fraction kAcaF1e that was composed of galactoglycerolipids, active against the growth of two of the four bacterial strains (Shewanella putrefaciens and Polaribacter irgensii) and all tested fungi. These promising results, in particular the isolation and the activity of galactoglycerolipids, attest the potential of the huge biomass of S. muticum as a source of new environmentally friendly antifouling compounds

High-value products from macroalgae: the potential uses of the invasive brown seaweed, Sargassum muticum

Marine seaweeds represent an abundant source of natural products and may harbour valuable chemicals. The brown seaweed Sargassum muticum is an invasive species to the coasts of the British Isles, mainland Europe and North America. Attempts at its eradication and control have generally not been successful, although time-consuming and costly. Commercial exploration of this biomass for food, fuel and pharmaceutical products could encourage its harvesting and control. Though S. muticum might be unsuitable as a source of biofuel due to high ash and water content, this rapidly growing macroalga has a naturally high content of antioxidants, carotenoids and phenols, including the well-known anti-cancer compound fucoxanthin, making this species a potential source of a range of pharmaceutically relevant material