Subcritical water extraction as an efficient technique to isolate biologically-active fucoidans from Nizamuddinia zanardinii.

Abstract A sulfated polysaccharide (fucoidan) has been isolated from Nizamuddinia zanardinii using subcritical water extraction method (SCWE), and extraction conditions were optimised using the response surface methodology. The optimum extraction conditions were found to be: extraction time of 29 min, extraction temperature of 150 °C, and raw material-to-water ratio of 21 g/mL. The fucoidan yield under these optimum conditions was 25.98%, which was considerably higher than that of conventional solvent extraction (5.2%). Extraction time and temperature were the extraction variables that most significantly affected fucoidan yield. Chemical and monosaccharide composition, molecular weight, and the antioxidant, anticancer and immunomodulatory activities of the extract have also been investigated. The monosaccharide composition of fucoidan included fucose (34.13%), mannose (30.70%), galactose (23.19%), xylose (9.35%) and glucose (2.65%). The average molecular weight of the extracted fucoidan was 694 kDa. Antioxidant results revealed that SCWE-extracted fucoidan had appreciable ABTS radical scavenging (70.35%) and reducing power (0.182 Abs). The anticancer activity of fucoidan ranged from 24.60 to 49.46% for HeLa cells and from 23.95 to 46.78% for HepG 2 cells. The NO production of RAW264.7 cells was observed to be dose-dependent, while maximum NO production was found to be 34.82 μmol at a 50 μg/mL fucoidan concentration. Graphical abstract Unlabelled Image Highlights • Subcritical water extraction (SCWE) was used to extract fucoidan from N. zanardinii. • Response surface methodology was used for optimization of extraction process. • Extraction time and temperature were the most influential factors. • High extraction yield of 25.98% was obtained with SCWE method. • SCWE-extracted fucoidan has appropriate antioxidant, anticancer and immunomodulatory activity. [ABSTRACT FROM AUTHOR]