Industrial optimization of fucoidan extraction from Sargassum sp. and its potential antioxidant and emulsifying activities

• Hot buffer extraction enhanced fucoidan yield and its sulfate content.
• Yield and sulfate content of fucoidan were optimized using Box–Behnken design.
• At optimum conditions, yield, and sulfate content were 19 and 47.6%, respectively.
• Chemical characteristics and antioxidant activity of fucoidan were elucidated.
• Crude fucoidan showed good emulsifying activity.

There is a growing demand to find an effective extraction process of sulfated polysaccharides from brown algae to conserve its structure and biological activity. Fucoidan was recovered from Sargassum sp. using a hot buffer extraction process. Box–Benhken experimental design was evaluated to study different conditions of temperature, pH and buffer: alga ratio on fucoidan yield and its sulfate content. By solving the regression equations and analyzing 3-D plots, the optimum conditions were at extraction temperature 60 °C, pH 4.0, and ratio of buffer: alga 10.0 mL/g. Under these conditions, the experimental fucoidan yield, and sulfate content were 19 and 47.6% (w/w), respectively, which were in good agreement with the predicted values. The use of hot buffer extraction was efficient to obtain a high fucoidan yield with maintaining high sulfate contents. Fucoidan preparations showed variations in antioxidant properties using various antioxidant assays. Increasing reducing antioxidant activity and hydroxyl radical scavenging of fucoidan extracts was attributed to increasing total sugars, fucose, and uronic acids. The data obtained suggested that the sulfate groups might act as reductones rather than radical scavengers to contribute to the antioxidant activity of fucoidan. Additionally, proteinaceous and phenolic compounds co-extracted with crude fucoidan contributed to its antioxidant potential. Crude fucoidan demonstrated good emulsion stabilizing capacities, especially with cedar wood oil and xylene. These results suggest the use of the crude fucoidan as a good alternative to many synthetic polymers, as well as other natural polysaccharides, in several applications in the food, pharmaceutical, cosmetic, textile, paper and petroleum industries.

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