Isolation and Characterization of Alginic Acid from Commercially Cultured Nemacystus decipiens (Itomozuku)

An alginate was isolated from commercially cultured Nemacystus decipiens which had been harvested in Yonashiro Town (Okinawa, Japan). The yield of the alginate was 1.6% (w/w of wet alga), and the uronic acid, ash and moisture contents of the alginate were 86.0%, 12.0%, and 2.3% (w/w), respectively. The molecular mass of the alginate was estimated to be about 1.5×10^5. The infrared spectrum and optical rotation of the alginate were in agreement with those of the standard alginate. D-Mannuronic acid and L-guluronic acid were identified by ^1H- and ^<13>C-NMR spectroscopy, the molar ratio of both sugar residues being estimated to be 0.72 : 1.00.