SIALIC ACIDS IN THE EXTERNAL MUCOUS SUBSTANCE AND THE CARTILAGE OF FISHES

Five kinds of sialic acid have so far been described1)2). In the present paper, the authors tried to identify and determine the sialic acids occurring in the external mucous substance from a sting ray, Dasyatis akajei, and an eel, Anguilla japonica, and in the cartilage of a shark, Carcharhinus gangeticus, a hammerhead, Sphyrna zygaena, and a sting ray. The isolation procedure of sialic acids was the same as that described in the previous paper3)4). Each material was hydrolyzed with 0.03N H2S04 at 80°C for 1 hr. The sialic acid liberated was retained on Dowex-1 (HCOO-), and then eluted with 0.3N HCOOH. The eluate was evaporated to dryness in vacuo at a temperature not exceeding 30°C. The residue was dissolved in water-methanol, and sialic acid was crystallized from the solution by adding ethyl ether. The identification of sialic acids was performed by paper chromatography developed with three kinds of solvent (Table 1). The content of sialic acid in each material was determined by SVENNERHOLM's resorcinol reaction8). Among the sialic acids only N-acetylneuraminic acid was identified in all the samples tested, and the unidentified substances positive to the “direct EHRLICH's reaction” were found, besides N-acetylneuraminic acid, in both the external mucous substance of an eel and the cartilage of a hammerhead. The content of sialic acid in each material tested was shown in Table 2.