Improvement of the extraction procedure for hyaluronan from fish eyeball and the molecular characterization

The object of this study was to improve the isolation procedure of hyaluronan and to compare characteristics of hyaluronan from the eyeball of bigeye tuna Thunnus obesus with other sources. General sources of hyaluronan are from Streptococcus zooepidemicus and rooster comb. Hyaluronan can be also obtained from the vitreous of fish eyes. Pure hyaluronan of higher molecular weight was obtained by the following improved extraction procedure: the frozen vitreous of a tuna eyeball was used to avoid contamination with blood, muscle tissue, and other factors; extracting was carried out over a long time period under cold conditions; cetylpyridinium chloride was used in order to separate mucopolysaccharides containing hyaluronan in the initial procedure without the process of removing fat and protein by reagents. The hyaluronan obtained was characterized by gel permeation chromatography, dynamic light scattering measurements, and viscometry. The characteristics of hyaluronan from tuna eyeballs were similar to those from other sources. However, the viscosity was lower. The possible reason could be ascribed to the wide distribution of molecular size in the vitreous humor of fish eye.