Vibrational spectroscopy of seaweed galactans

• Published in: Hydrobiologia 1996-07, Vol.326-327 (1), p.481-489
• Main Author: Matsuhiro, Betty
• Format: Article
• Language: English
• Subjects: Gelidium; Gracilaria; Iridaea obovata; Marine
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/BF00047849

Information from classical infrared spectroscopy studies has been of significance for characterizing seaweed galactans. The development of Fourier transform infrared spectroscopy and of Fourier transform laser Raman spectroscopy has produced great advances in the application of vibrational spectroscopy to the structural study of polysaccharides. Computational facilities in the spectrometers allow the arithmetic manipulations of the spectra. The second-derivative mode in the FT-IR spectroscopy provided more information by increasing the number and resolution of the bands in the spectra as compared to the parent ones. A review of literature data on vibrational spectroscopy of sulfated polysaccharides and new results are presented. Agar-type polymers showed two diagnostic bands in the second-derivative mode in the region 800-700/cm. Carrageenans exhibited a number of bands in the region 1600-1000 /cm. Fourier transform laser Raman spectroscopy in the solid state gave well-defined characteristic spectra of agar and carrageenans. Both techniques can be applied to small samples in the solid state and allow differentiation in a few minutes between agar and carrageenan-type seaweed galactans. The second-derivative mode of the FT-IR spectra can be applied to distinguish agar-producing from carrageenan-producing seaweeds. The spectra on KBr pellets of dried, ground agarophyte and carrageenophyte seaweed samples showed the same bands as the corresponding polysaccharides.