Purification of a fucoidan from kelp polysaccharide and its inhibitory kinetics for tyrosinase

High-speed countercurrent chromatography (HSCCC) was used to separate kelp polysaccharide. HSCCC was performed using an aqueous two-phase solvent system composed of PEG1000–K2HPO4–KH2PO4–H2O (0.5:1.25:1.25:7.0, w/w) by eluting a lower aqueous phase at 2.0 mL/min at 600 rpm, yielding two separate fractions, KPS-1 and KPS-2. The KPS-2 fraction was further purified by DEAE-Sepharose fast flow anion-exchange column chromatography to provide 3 fractions, KPS-2-1, KPS-2-2 and KPS-2-3. GPC–HPLC analysis indicated that KPS-2-1 fraction was a purified fucoidan. FT-IR analysis showed that KPS-2-1 was a sulphated polysaccharide. An analysis of enzymatic kinetics showed that the purified fucoidan was a competitive inhibitor of tyrosinase toward l-tyrosine, and the inhibitory constant Ki obtained from double-reciprocal plots was 0.9907 mg/mL.