## 4 Discussion  
The abundance of polysaccharides in the naturally occurring sea algae is directly associated with the presence of several kinds of biomolecules. Furthermore, the polysaccharides in the marine animals vary greatly from those in the terrestrial habitats. In addition to fucoidan, marine brown algae have been shown to include sulfated polysaccharides, such as alginate, which are not observed in other macroalgal species. The sulphate concentration of fucoidan was 8.07 \(\pm\) 0.13%, which was much lower than the value reported for sulfated polysaccharides isolated from abalone [13]. The confirmation experiment results are closely connected to _Sargassum_ sp. having a sulphate concentration of 47.6 \(\pm\) 0.59% _w/w_ by utilizing distilled water at 65 \({}^{\circ}\)C [11; 48]. Sulfate (7.56%) and uronic acid (0.32%) were found in _S. fluitans_[49]. Carbohydrates, galactose, uronic acid, and sulphate groups were slightly changed depending on the extraction technique, season, and local environmental variations. However, the chemical composition of some species, such as _S. polycycystum_, _S. graminifolium_, and _S. wightii_ are different [50; 51; 52]. Brown algal sulfated polysaccharide monosaccharide composition varies based on species, the extraction process, location, and climatic conditions [53; 54; 55]. The chemical composition of fucoidan changed according to the extraction procedure, analytical methodology, season, and location. _Sargassum tenerium_ had 16.33% uronic acid, 39.04% fucose, 7.62% mannose, 31.50% galactose, and 56.89% carbohydrate. The presence of fucose (59.3 \(\pm\) 0.43%) showed the carbohydrate content of isolated fucoidan [4]. A similar study was reported in _Turbinaria decurerens_, and the fucose content (59.3%) is present [55]. The xylose (3.01%) is present in _M. oxysporum_[56]. The molecular weights of fucoidan might vary depending on geographical location, harvesting season, and species. The physical and chemical characteristics of these fucoidans varied depending on the species and population age [57]. The molecular weight varied in _U. pinnatifida_ (51.7 kDa), _S. latissimi_ (395.4 kDa), and _Cladosibion_ sp. (1927.2 kDa) [38]. Fucoidan isolated from _U. pinnatifida_ had an MW of around 378 kDa. The solubility of seaweed was more or less prevalent in _S. wightii_ and _S. plagiophyllum_[51; 33]. Fucoidan derived from _S. fusiforme_ had an MW of 12.4 kDa and a sulphate content of 7.5%, which did not inhibit angiogenesis in the HMEC-1 cells [8]. As for bioactivity, the molecular weight serves two functions. In general, high-molecular-weight fucoidans are more effective than low-molecular-weight fucoidans. However, low-molecular-weight fucoidans have superior pharmacokinetic properties [58]. The solubility of fucoidan from _S. plagiophyllum_ and _Fucus vesiculos_ was the highest in water and DMSO [59; 37]. All seaweeds exhibited the highest weight loss between 170 and 280 \({}^{\circ}\)C, which was related to the high carbohydrate contents of three species, such as _Sargassum Huntergii_, _Mustocarpus stellatus_, _Ulva_ sp. [60]. In the last stage (550-800 \({}^{\circ}\)C), the weight of the seaweeds barely changed, and the remaining weight represented the ash content, which might contain the minerals of polysaccharides, such as sulfates, phosphates, and carbonates [61]. The FT-IR spectrum analysis of marine algae _Chondrus crispus_ and lambda-carrageenan showed two weak bands at 815 and 830 cm\({}^{-1}\), which was consistent with the previous results [62]. The FT-IR analyses of marine brown algae _P. pavonica_ and _S. vulgarve_ revealed a wide band (about 1195-1237 cm\({}^{-1}\) for _Padina_ and 1210-1280 cm\({}^{-1}\) for _Sargassum_) ascribed to (S=O), a distinctive part in fucoidan [63]. The NMR study showed the chemical shift of fucoidan at anomeric signal of 5.00-5.5 ppm, revealing that L pyrenose was concentrated in fucoidan [64]. The signals at 4.681 corresponded to 3-linked \(\alpha\)-L-fucose, which was the main constituent of fucoidan [65].