Compositions, methods, systems, etc., are provided for modified and/or purified fucans and corresponding fucan-containing compositions that inhibit fibrous adhesions among other advantages. The purified/modified fucans and fucan compositions have a reduced level of non-fucan components or impurities such as those found in a starting fucan composition. Such reduced undesirable components or impurities include, for example, undesired components bound to the fucan and compounds in the composition that are not a part of or bound to the fucan.