with the dye and easily washed out from the finished products [52]. Conventional pharmaceutical industry has been using alginate and its derivatives as thickening, stabilizing and gel-forming agents, as they have a significant role in controlled-release drug products [46] and has recently been used in the form of nanoparticles (e.g. hydrogels, beads) in drug delivery systems, especially in protein delivery [53–55].
4.1.4 Fucoidan
Fucoidans, also named as fucan or fucosan, are fucose-containing sulfated polysaccharides contain l-fucose and sulfate esters and placed in intracellular tissues of brown seaweeds [56]. Like other seaweed polysaccharides, fucoidans are also differ in structure among the species. Seaweed species which can have fucoidans are Laminaria, Fucus, Macrocystis and Himanthalia [56–60]. Some other species which have been studied in literature to obtain fucoidans are Cladosiphan, Adenocystis, Ascophyllum and Sargassum [56, 60–63]. Fucus vesiculosus is the most known fucoidan source, its chemical composition is relatively simple (Figure 4.5) as generally consists of, fucose linked sulfate groups, α-(1–3)-l-fucopyranose. Among the species the chemical composition is becoming complex where they contain various monosaccharides in small amounts (Table 4.1).
The earlier fucoidan extraction is based on hydrolyzing the non-fucoidan structure with acetic acid or hydrochloric acid. For the last seventy years many modifications were studied on the extraction and purification methodology for fucoidans [56, 60–62, 69, 70]. These studies obtained fucoidan with α-(1–3)-l-fucopyranosyls or α-(1–4)-l-fucopyranosyl residues which are sulfate substitutes and with different monosaccharides-linked structures. As Ale et al. [60] demonstrated the term “fucoidan” is a name of a wide family of fucosecontaining sulfated polysaccharides and corrected the name “fucoidan” as fucosecontaining sulfated polysaccharides. However, despite the different structured-last products obtained after the extraction, the earlier acidic extraction method with temperature elevation is still the preferred nowadays.
Figure 4.5 Fucoidan structure.
Table 4.1 Composition of fucoidans from different seaweed species.
| Species | Composition | References |
|---|---|---|
| Cladosiphon okamuranus | Fucose, glucose, urinic acid, sulfate | [62] |
| Fucus vesiculosus | Fucose, sulfate | [64, 65] |
| Macrocysstis pyrifera | Fucose–galactose, sulfate | [64] |
| Fucus evanescens Fucus serratus | Fucose–sulfate–acetate | [66, 67] |
| Laminaria angustata | Fucose–galactose–sulfate | [68] |
| Himanthalia lorea | Fucose, xylose, sulfate | [69] |
| Adenocytis utricularis | Fucose, galactose, mannose, sulfate | [70] |
Fucoidan, like many seaweeds, has been consumed for a long time in Asian countries, and also used as a nutraceutical and cosmeceutical all around the world. Due to the biological activities, such as anticoagulant, antithrombotic, antitumor, antivirus, anti-proliferative, anti-inflammatory etc. their application interest is high in biological and life sciences. One of the application areas is as a dietary supplement as capsules and a powder supplement for beverages to enhance the immune system. In food industry, these sulfated polysaccharidecontained seaweeds, which have a prebiotic property, are used as a food supplementary for nutritional and functional food formulation. Anticoagulant, antimicrobial and anti-biofilm activities of fucoidans are used in dental applications. The ability to absorb directly by the human skin, as a cosmeceutical in topical cosmetics, fucoidans are used for whitening, preserving moisture, removing freckles in cosmetic industry [11, 60, 71–77].
4.1.5 Laminaran
Laminaran or Laminarin, is a brown seaweed polysaccharide found in plastids of the cells. It is a linear polysaccharide mainly in a form of β-(1–3)-d-glucans with the branches of β-(1–6)-D-glucosyl, and at the ends of the polymeric chains d-mannitol or d-glucose residues are seen (Figure 4.6). The ratio of each chain and structure are varying from species to species and with growth environment conditions. The main laminarin-rich seaweed species are Laminaria, Saccharina, Ascophyllum and Fucus. Laminaria and its derivatives, sulfated laminaran and oligo-laminaran which are obtained by chemical modifications, are biologically active.
The extraction procedure (Figure 4.7) is in many pathways [65, 69, 78, 79]. Laminaran is extracted together with the alginate and fucoidan and exactly needs purification steps. Calcium chloride added extraction is preferred to prevent solubilization of alginate, and because of being smaller molecular weight, laminaran can be separated from fucoidan by using ultrafiltration [11, 76, 77]. There is also a water extraction and a centrifugation for purification step, to precipitate alginate and fucoidan together.
Figure 4.6 Laminaran structure with (a) d-mannitol and (b) d-glucose residues.
Figure 4.7 Laminaran extraction procedure.
Laminaran is a nonfood grade polysaccharide like fucoidan. Nevertheless, laminaran is used as a dietary fiber supplementation. Because of its oligo-structure it is used by the microbial 0biota in gut which helps to prevent colon cancer [80–82]. The main applications are in clinical and pharmaceutical, mainly in cancer treatments, for its activities of anticoagulant, antimetastatic and tumor inhibiting activities. Laminaran, in cosmeceutical application, is used to increase the rate of the production of reconstructed dermis [83].
4.1.6 Ulvan
Ulvan is a sulfated cell-wall polysaccharide of the green algae, Ulva sp. It is mainly made up of l-rhamnose, d-xylose, d-glucose, d-glucuronic acid [11] and small amounts of sulfate groups positioned in xylose and rhamnose units [84–86].
To date ulvan is the less studied and investigated seaweed polysaccharide. Ulvan’s rheological properties are attractive and because of this, ulvan is considered as a food-grade polysaccharide [29]. It has a unique gel-forming mechanism, quiet complex and not yet understand, which make ulvan viscous than Arabic gum. Ulvan polymers and oligomers have comprehensive biological and pharmacological activities, such as antioxidant, antihyperlipidemic, proliferation, adhesion, anti-tumoral and anti-influenza [11, 30, 85–86]. In formation of biodegradable films, ulvan has an application area, for minimizing the microbial population.
4.2 Conclusion
Seaweeds