**4. How to Prepare**

Fucoidan contents of brown seaweeds depend on a lot of factors such as variety, harvesting season, and maturity stage of seaweeds. In general, polysaccharides available in seaweeds can be extracted using water with or without some special enzymes, and separated by adding organic solvents [6]. However, extractions of cell wall polysaccharides

**Citation:** Sanjeewa, K.K.A.; Jeon, Y.-J. Fucoidans as Scientifically and Commercially Important Algal Polysaccharides. *Mar. Drugs* **2021**, *19*, 284. https://doi.org/10.3390/ md19060284

Received: 14 May 2021 Accepted: 18 May 2021 Published: 21 May 2021

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are little bit difficult with the solvent extraction process. To extract cell wall polysaccharides such as fucoidan requires lyases in order to increase the extraction efficiency. Therefore, an enzyme-assisted extraction technique can be employed as an alternative method to enhance the extraction efficiency of fucoidan for industrial use [7].

In the article by Dörschmann, P. et al. [8], the authors enzymatically extracted *Saccharina latissima* fucoidan and isolated its low-molecular weight fraction. The results showed that the enzyme-treated fucoidans and the fractionated low-molecular-weight fucoidans are very promising for beneficial age-related macular degeneration-relevant biological activities. In order to modify fucoidans in molecular weights, fucoidans can be hydrolyzed by enzymes or phyco-chemical treatments and the resultant smaller fucoidans or fucoidan oligomers might improve bioactivities. In this Special Issue, a native fucoidan extracted from *Sargassum crassifolium* pretreated by single-screw extrusion was degraded by ascorbic acid or hydrogen peroxide. The lower-molecular-weight fucoidan prepared by ascorbic acid exhibits the highest cytotoxicity to A-549 cells and a strong ability to suppress Bcl-2 expression [9]. Tan, J. et al. [10] isolated fucoidan from *Saccharina japonica* and prepared its depolymerized fragment by oxidant degradation. The molecular weights of Fucoidan and its depolymerized fragment were 136 and 9.5 kDa, respectively. The low-molecular-weight fucoidan had higher renoprotective activity on adriamycin-induced nephrotic syndrome. On the other hand, Zayed, A. and Ulber, R. [11] mentioned in their review article that since a universal protocol for fucoidans production has not been established yet, all the currently used processes were presented and justified. The review article in the fucoidans field provided an updated overview regarding the different downstream processes, including pre-treatment, extraction, purification and enzymatic modification processes, and shows the recent non-traditional applications of fucoidans in relation to their characters.
