According to the summary, the polysaccharide first discovered by Kylin in 1913 was initially named “fucoidin”. Now it called fucoidan, but some also called it fucan, fucosan or sulfated fucan. As noted by Li at al, the commercially available fucoidan from Fucus vesiculosus is composed of 44.1% fucose, 26.3% sulfate and 31.1% ash, with small amount of aminoglucose. The structural model of fucoidan suggested by Conchie was accepted for 40 years, until 1993, when it was revised by Pankter at al, primarily due to differences in extraction methods.
The review by Li at al mentions Ponce at al reporting different results from various extraction methods.
The structural diversity of fucoidans makes a detailed structural analysis of those molecules difficult. The primary components of fucoidans are fucose and sulfate groups; other components are galactose, xylose, mannose and uronic acid. Various biological functions correlate with specific structural configurations of the compounds. According to Thanh in an article published in Marine Drugs in 2013, determining the molecular and special structure is important in evaluating the application of a specific polysaccharide. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3736432/ (full text). The scientists determined the structure and built a molecular model of fucoidans from Turbinaria ornata from the Sargassaceae family.
Jin at al from the Chinese Academy of Science in Quingdao characterized a fucoidan extracted from Saccharina japonica and fractionated by anion exchange chromatography. It was shown that fucose was sulfated at C2 or C4 while galactose was sulfated at C2, C4 or C6. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3497013/ (full text)
Sargassum mcclurei is a species from which three different fucoidan fractions were purified and characterized by Thinh at al. In their publication in Marine Drugs, the researchers point out the great versatility of fucoidan structure. For example, commercially available fucoidan from Fucus vesiculosus contains 16 different sulfated polysaccharides with varying proportions of the individual monosaccharide residue. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3707154/ (full text)
Studies have shown differences in fucoidans collected at different life stages of the organisms. For example, scientists from Vladivostock, Russia, Anastyuk at al observed such variations when characterizing four fucoidan fractions from Costaria costata, collected at vegetative and at generative stages. One set exhibited high fucose content and substantial percentage of hexoses and uronic acid and lower sulfate content, the other highly sulfated galactofucan. http://www.ncbi.nlm.nih.gov/pubmed/22840031
Another group of Russian scientists, Vishchuk at al, characterized fucoidans isolated from vegetative and reproductive tissue of Alaria spp. and Saccharina japonica. The fucoidan yield was 5.7% (w/w on dried alga basis) from fertile and 3.8% from sterile Alaria sp. and 1.42 and 0.71% for fertile and sterile S. japonica respectively. The fucoidans from both fertile algae had a slightly higher degree of sulfation and somewhat more homogenous monosaccharide composition.
A comparative study of polysaccharides from reproductive and sterile tissues from five brown algae from the Russian far east seas was also conducted by Skriptsova at al. Fucoidan content in fertile tissue was shown to be 1.3-1.5 times higher than in sterile ones. Fucoidan synthesized by fertile plants was less hetrogenous in monosaccharide composition in comparison to sterile tissue. Structural changes are species specific. http://www.ncbi.nlm.nih.gov/pubmed/22072046
Consistently higher fucoidan yield from sporophyl, as compared to the frond of Undaria pinnatifida, was also reported by researchers from New Zealand, Mak at al. http://www.ncbi.nlm.nih.gov/pubmed/23618312
A taxonomic comparison of fucoidan structure can be found in the 2011 overview by Ale at al, page 5-9.
Ale at al provide a historical overview of fucoidan extraction methods. The available data, according to the researchers, show that the term “fucoidan” has been used for diverse chemical structures. Ale at al suggest that it is more correct to use the term fucose-containing sulfated polysaccharides (FCSP) rather than fucoidan as a collective term for those polysaccharides. Discussion on the various extraction methods can be found on pages 2-5 of this 2011 publication. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3210621/
Than at al followed fucoidan extraction method by Bilan at al, which they described in their article in Marine Drugs. Dried seaweed was treated at room temperature with a 4:2:1 MeOH – CHCl3 – water mixture to remove colored matter, filtered and vacuum dried. This material was extracted with 2% CaCl2 solution under mechanical stirring at 85 C for 8 hours. An aqueous hexadecyltrimethylammonium bromide solution (10%) was added to the extract. The obtained precipitate was centrifuged, washed with water, stirred with 20% ethanolic NaI solution for 2-3 days at room temperature, washed with ethanol and dissolved in water. The solution was dialyzed. Fucoidan was concentrated and recovered as sodium type by freeze-drying. The yield of fucoidan was 2.215% based on the dried seaweed weight.
In an article published in 2012 in the Indian Journal of Pharmaceutical Sciences, Badrinathan at al describe extraction of sulfated polysaccharides from Sargassum myriocystum according to the method by Silva at al. Algal powder was incubated overnight in acetone to remove lipid and pigments. The residue was dissolved in 5 volumes of 0.25M NaCl, with the pH monitored periodically and adjusted to 8 using NaOH. Trypsin was added for proteolysis and incubated 24 hours. After incubation the precipitate was filtered through cheese cloth, and the filtrate was precipitated using ice-cold acetone under gentle agitation at 4 C. The formed precipitate was centrifuged and dried under vacuum. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3687925/ (full text)
Thanh at al report tandem electrospray ionization mass spectrometry (tandem EIMS) to be useful in determining the chemical structure of fucoidans. With the development of high resolution processes, such as scattering techniques (light scattering, X-ray and neutron scattering), it is possible to study the configuration of a polysaccharide on a molecular level. Small Angle X-Ray Scattering (SAXS) is a powerful technique providing high resolution view and helping determine the configuration of a molecule in a solution. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3736432/ (full text)
Lee at al described a simple, selective and rapid method for determination of fucoidans using methylene blue staining of sulfated polysaccharides, immobilized into filter paper and consequent optical density measurement of the dye eluted from the filter paper. The solid phase method allows selective determination of 1-20 micrograms of fucoidan in the presence of potentially interfering compounds.
Gomez-Ordonez at al developed a high performance, size-exclusion chromatography method (HPSEC) to evaluate molecular weight distribution of algal polysaccharides. http://www.ncbi.nlm.nih.gov/pubmed/22483892
Controversial data may be found in literature, even about the structure of the most carefully studied fucoidans from Fucus vesiculosus. Li at al suggest in their review that specific enzymatic methods can be used to simplify the structure of fucoidan and reduce the difficulty of analysis. http://www.mdpi.com/1420-3049/13/8/1671 (full text)
Frequently low molecular weight fucoidans show enhanced bioactivity. Polish researchers, Pielesz at al, suggested mild acid hydrolysis as an efficient tool to study the relationship between the molecular weight of sulfated polysaccharides and their biological activities. http://www.ncbi.nlm.nih.gov/pubmed/21703598 Choi and Kim noted disadvantages of enzymatic degradation or acid hydrolysis, such as narrow substrate specificity or unfavorable hydrolysis of side groups, respectively. The South Korean scientists obtained low molecular weight fucoidans by gamma radiation. The molecular weight of samples irradiated at 10 kGy rapidly dropped to 38 kDa, then gradually decreased to 7 kDa, without significant elimination of the sulfate groups. http://www.ncbi.nlm.nih.gov/pubmed/23911457 Choi at al has also used the gamma irradiation technique to obtain low molecular weight polysaccharides in a study published in 2009.
Fucoidans from seaweed biomass have been studied extensively for their potential biological activities
Adenocytis utricularis, Alaria ochotensis, Alaria sp., Ascophyllum nodosum, Bifurcaria bifurcata, Chorda filum, Costaria costata, Dictyota menstrualis, Eclonia curome, Fucus distichus, Fucus evanescens, Fucus serratus, Fucus vesiculosus, Himanthalia lorea, Hizikia fusiforme, Laminaria angustata, Lessonia vadosa, Macrocystis pyrifera, Padina gymnospora, Padina pavonia, Pelvetia wrightii, Saccharina japonica, Sargassum denticaprum, Sargassum horneri, Sargassum linifolium, Sargassum mcclurei, Sargassum myriocystum, Sargassum oligocystum, Sargassum palidum, Sargassum polycystum, Sargassum stenophyllum, Sargassum swartzii, Sargassum trichophyllum, Silvetia babingtonii, Stoechospermum marginatum, Turbinaria ornate, Undaria pinnatifida
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