Structure of Fucoidan and Isolation Techniques

Fucoidans exhibit various biological activities, including immunomodulation, anti-cancer, and pathogenic inhibition. This approach can be used to isolate numerous natural resources and various applications in the pharmaceutical, food, and cosmetic industries. Fucoidan surrounds sulfated L-fucose as a vital monosaccharide and small amounts of mannose, galactose, glucose, xylose, arabinose, uronic acid, and glucuronic acid. Structural analysis revealed that purified fucoidan consists of a carbohydrate chain composed mainly of (1→3)-linked or (1→4)-linked Lfucose residues, with sulfate groups at C-2 and C-4 positions. Fucose residues at C-3 or C-4 serve as branch sites for galactose residues with 1–4)-linkages. Low molecular weight fucoidan, medium molecular weight fucoidan, and high molecular weight fucoidan are the three different types of fucoidan based on molecular weights. The structure of fucoidan determines its bioactivity and its economic and commercial value depending on the species, geographical location, and harvest season. Therefore, shortened phases, low temperatures, and low acidity are used in the extraction technique to determine the distinct structures of fucoidans. In industrial manufacturing, the extraction techniques must be environmentally friendly and cost-effective. In this chapter, classical extraction and purification procedures such as hot water, acidic or alkaline extractions, and chromatographic techniques are discussed and detailed. Microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), and enzyme-assisted extraction (EAE) are innovative techniques for fucoidan extraction. Optimization strategies for pH, temperature, pretreatment conditions, extraction time, and yield parameters also discussed in detail.