Abstract: Disclosed is an economical method for the preparation of chondroitin sulfates A and C useful as an effective ingredient of medicaments from fish scales as a waste material discharged from fishery in large quantities. Fish scales are enzymatically decomposed in an aqueous medium in the presence of a protease to isolate the chondroitin sulfate compounds and by-product polypeptides followed by removal of the by-product polypeptides from the aqueous solution by a cation-exchange treatment and then the aqueous solution of the chondroitin sulfate compounds is subjected to fractional precipitation by the addition of ethyl alcohol as the precipitant.

Abstract: Disclosed is an efficient and economical method for the preparation of N-glycolyl neuraminic acid in a high purity from an inexpensive abundant source material. The method comprises dispersing body tissues of an echinodermatous marine animal Cucumaria echinata in an aqueous medium, preferably, using a dry powder of the tissues prepared in advance, in which the tissues are proteolytically decomposed to isolate N-glycolyl neuraminic acid in the form of an aqueous solution containing polypeptides as a by-product, followed by separation of N-glycolyl neuraminic acid from the aqueous solution by removing the polypeptides and purification of the compound in a process utilizing an ion-exchange treatments.