Fucoidans are marine sulfated biopolysaccharides that have heterogenous and complicated chemical structures. Various sugar monomers, glycosidic linkages, molecular masses, branching sites, and sulfate ester pattern and content are involved within their backbones. Additionally, sources, downstream processes, and geographical and seasonal factors show potential effects on fucoidan structural characteristics. These characteristics are documented to be highly related to fucoidan potential activities. Therefore, numerous chemical qualitative and quantitative determinations and structural elucidation methods are conducted to characterize fucoidans regarding their physicochemical and chemical features. Characterization of fucoidan polymers is considered a bottleneck for further biological and industrial applications. Consequently, the obtained results may be related to different activities, which could be improved afterward by further functional modifications. The current article highlights the different spectrometric and nonspectrometric methods applied for the characterization of native fucoidans, including degree of purity, sugar monomeric composition, sulfation pattern and content, molecular mass, and glycosidic linkages.

Metabolism of 7-O-methylnaringenin (sakuranetin) by Cunninghamella elegans NRRL 1392 yielded naringenin and naringenin-4′-sulfate. C. elegans also converted 5, 3′, 4′-trihydroxy-7-methoxyflavanone into eriodictyol-4′-sulfate. Furthermore, incubation of 5, 4′-dihydroxy-7, 3′-dimethoxyflavanone with the same fungus gave homoeriodictyol (5, 7, 4′-trihydroxy-3′-methoxyflavanone) and homoeriodicytol-7-sulfate. The structures of the new metabolites were established by spectral analysis including 2D-NMR, HR-ESI-FT-MS beside hydrolysis by acid.