Influence of molecular weight on the properties of Sargassum muticum fucoidan

The crude fucoidan extracted during hydrothermal treatment of Sargassum muticum was fractionated in a sequence of membranes (100 to 5 kDa) operating at a volume concentration ratio (VCR) of 5. The retentates and final permeate were further characterised for molecular weight, oligosaccharide content, sulfate and phenolic content, as well as for radical scavenging properties, expressed as Trolox equivalent antioxidant capacity (TEAC). The 50-100 kDa fraction contained 25% of solubles in the hydrolysates. The highest oligosaccharide content (69.34 g 100 g(-1)) was found in the 50-100 kDa fraction, whereas the maximal sulfate (12.30 g 100 g(-1)) and phenolic (6.63 g 100 g(-1)) content occurred in the > 100 kDa fraction, which also presented the highest antiradical potency, 47 g Trolox-eq 100 g(-1). However, the 10-30 kDa fraction was the most cytotoxic against cervix cancer HeLa 229 cells (EC50 = 44 mu g(-1)). As a consequence, the membrane fractionation of the liquid phase obtained by autohydrolysis could provide fucoidans with different composition, molecular weight and properties.