Size distribution and chain conformation of six different fucoidans using size-exclusion chromatography with multiple detection.

•SEC with multiple detection is useful for structural characterization of fucoidans.•Six fucoidans were heterogeneously and complex composed.•Six fucoidans considerably differed in their molar mass and size characteristics.•Typical fucoidans consisted of expanded flexible chains with branched structure.•Molar mass and conformation of fucoidans influence their biological activities.