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We assessed the antioxidant activity of crude extracts from 24 rhodophyte species from Brittany coasts using three complementary methods (2,2-diphenyl-1-picryhydrazyl, reducing activity, and b-carotene-linoleic acid system). We also examined phenolic contents. Cytotoxic activities were determined with three different cancer cell lines. Four species (Aglaothamnion pseudobyssoides, Furcellaria fastigiata, Polysiphonia lanosa, and Heterosiphonia plumosa) had high antioxidant activity and high phenolic content. The extract from Brongniartella byssoides had the highest antioxidant potential, which was also found to be equivalent to the antioxidant activities of some commercial antioxidants. In the b-carotene system, extracts from Porphyra leucosticta and Porphyra purpurea had some specific antioxidant activity. Furthermore, Asparagopsis armata, B. byssoides and H. plumosa extracts had strong cytotoxic activities against Daudi and Jurkat cells.

Significance and Impact of the Study: With the constant increasing of bacterial resistance against known antibiotics in worldwide public health, it is now necessary to find new sources of antimicrobials. Marine bacteria from New Caledonia were isolated, tested for antibacterial activity and characterized to find new active molecules against multidrug-resistant bacteria. This study illustrates the diversity of the marine ecosystem with potent new bacteria species. Also the potential of marine bacteria as a rich source of bioactive molecule, for example antibiotics, is highlighted. AbstractMarine bacteria are a rich source of bioactive metabolites. However, the microbial diversity of marine ecosystem still needs to be explored. The aim of this study was to isolate and characterize bacteria with antimicrobial activities from various marine coastal environment of New Caledonia. We obtained 493 marine isolates from various environments and samples of which 63 (12Á8%) presented an antibacterial activity against a panel of reference pathogenic strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis). Ten out of the most promising strains were cultured, fractionated and screened for antibacterial activity. Four of them (NC282, NC412, NC272 and NC120) showed at least an activity against reference and multidrug-resistant pathogenic strains and were found to belong to the genus Pseudoalteromonas, according to the 16S phylogenetic analysis. The NC282 strain does not belong to any described Pseudoalteromonas species and might be of interest for further chemical and biological characterization. These findings suggest that the identified strains may contribute to the discovery for new sources of antimicrobial substances to develop new therapies to treat infections caused by multidrug-resistant bacteria.

International audienceThe red alga Mastocarpus stellatus is widely found on the coastline of Brittany (France) and it was previously reported to contain high amounts of floridoside, a well-known glycoside in red algae. Therefore, we aimed at evaluating the potential interest of M. stellatus for industrial purposes. Floridoside extraction was optimized, hydroethanolic mixture being the most efficient extractant compatible with industrial requirements. Floridoside yield was increased significantly through pre-treatment and conditioning of the alga before extraction. Thus, salt stress and drying procedure both resulted in an increase in floridoside concentration. Studies of seasonal variations of floridoside content in this species showed that maximal levels were recovered in autumn. We now propose an optimized procedure for M. stellatus valorization, especially for biomedical applications