Alginate, mannitol, phenolic compounds and biological activities of two range-extending brown algae, Sargassum mangarevense and Turbinaria ornata (Phaeophyta: Fucales), from Tahiti (French Polynesia) Zubia, M. /Payri, Claude Deslandes, E. Sargassum mangarevense Turbinaria ornata Alginate Mannitol Phenolic compounds Biological activities This study deals with two range-extending brown algae from Tahitian coral reefs, Sargassum mangarevense and Turbinaria ornata; their alginate properties, mannitol and phenolic contents, antioxidant and antimicrobial activities were determined. Turbinaria ornata showed the richest alginate content with the highest extraction yield (19.2 +/- 1.3% dw). Their alginates also exhibited the highest viscosity (50 +/- 18 mPa. s), but the M: G ratios (mannuronic acid to glucuronic acid) of alginates (1.25-1.42) were similar in both species. Alginate yield displayed spatial variations, but no significant seasonal changes. The highest mannitol content was found in S. mangarevense (12.2 +/- 2.1% dw) during the austral winter. With respect to other tropical Fucales, both algae exhibited also a high phenolic content (2.45-2.85% dw) with significant spatio-temporal variations. Furthermore, high antioxidant activity and activity against Staphylococcus aureus were also detected in extracts. According to these preliminary results, these two range-extending algae are of key interest in numerous industrial areas. 2008 text https://www.documentation.ird.fr/hor/fdi:010044141 fdi:010044141 Zubia M., Payri Claude, Deslandes E.. Alginate, mannitol, phenolic compounds and biological activities of two range-extending brown algae, Sargassum mangarevense and Turbinaria ornata (Phaeophyta: Fucales), from Tahiti (French Polynesia). 2008, 20 (6), 1033-1043 EN