Fucoidan, a fucose-rich sulfated polysaccharide found predominantly in brown macroalgae, exhibits diverse bioactivities and holds great potential for pharmaceutical applications and for natural therapeutics integration. Their medicinal properties have driven demand for highly specific isolation techniques capable of yielding high purity fucoidans from complex seaweed extracts, that commonly contain different potential contaminants. This study developed a purification protocol for the direct recovery of fucoidan from Ecklonia maxima extracts employing dye-affinity chromatography, using toluidine blue O (TBO) and azure A (AA) immobilized ReliZyme™ EA112. Adsorption experiments with a fucoidan standard enabled an initial evaluation of the adsorption kinetics and adsorbent capacities. Strong metachromatic complexation between the anionic polysaccharide and cationic thiazine dyes led to approximately 84% (AA) and 67% (TBO) of the adsorption occurring within the first 24 h. The kinetic data was best described by the pseudo-second-order model, while adsorption isotherms indicated multilayer adsorption and adsorbent capacities of 150.0 and 178.2 mg fucoidan·g −1 adsorbent for TBO and AA, respectively. An average recovery of 87.6% was achieved, with no reduction in adsorption capacity after three adsorption–desorption cycles. Investigation of fucoidan adsorption from synthetic mixtures and real crude extracts revealed reduced adsorption capacities, with adsorbents from the real extract additionally exhibiting prominent staining (presumably from polyphenols). FTIR confirmed the isolation of fucoidan from E. maxima crude extracts, while molecular weight distribution and elemental analysis verified the effectiveness of the purification protocol. Collectively, the results support DAC purification as a robust strategy for the recovery and isolation of fucoidan directly from aqueous extracts without the use of prior ethanol precipitation. • Purification of fucoidan by dye affinity chromatography from Ecklonia maxima. • Toluidine blue O and Azure A immobilized adsorbents have maximum capacities of 150.0 and 178.2 mg fucoidan/g adsorbent, respectively. • High fucoidan selectivity - negligible adsorption of alginate. • Fucoidan purity improved up to 1.70-fold without additional pre- and post-processing steps.
Wilkinson et al. (Fri,) studied this question.