Ultrasound-assisted extraction of fucoidan from Sargassum muticum

Ultrasound-assisted aqueous extraction (USAE) of crude fucoidan from Sargassum muticum using an ultrasonic bath (150 W and 40 kHz ) at room temperature (25 °C) for 5–30 min was studied. Fucoidan-containing extracts were separated by centrifugation and characterized by HPLC, HPSEC, FT-IR, and MALDI-TOF spectrometry. Crude fucoidan on the best conditions was composed by oligosaccharides of fucose:galactose:glucose:xylose:mannose:rhamnose in a mass ratio of 1:0.70:0.33:0.27:0.22:0.10. The maximum sulfate content was 39.54 ± 0.001-mg sulfate ion g−1 extract. Furthermore, extract contained 25-mg phlorotannins g−1 extract and showed an ABTS radical scavenging activity equivalent to 40-mg Trolox g−1 extract measured with the Trolox Equivalent Antioxidant Capacity (TEAC) assay. The cell viability of selected tumoral human cell lines was reduced up to 30% in the presence of crude extracts at 500 mg L−1.