Regional Difference of Alginates Extracted from Different Brown Seaweeds

Abstract

Alginate, fucoidan and laminarin are the three main polysaccharides found in brown seaweeds with various bioactive functions. Alginate has relatively large molecular weight with high viscosity, combing with M (homo-polymeric) and G blocks (hetero-polymeric). Different conformations and chemical structures of M and G blocks will affect the bioactive functions. In order to analyze the regional difference, six brown seaweeds were collected from different locations. Saturated and unsaturated alginate oligosaccharides were prepared for NMR and LC-MS/MS analysis. Podina from Malaysia belongs to high G species; Whereas Laminaria japonica from Shandong and Fujian belongs to high M species; Laminaria saccharina from U.S., Laminaria digitata from Iceland, and Ascophyllum nodosum from Indonesia are defined as intermediate alginates. Thus, Podina can provide brittle gel while the other five species produce elastic gels. In addition, two Laminaria species from China have similar M/G ratios, and Laminaria saccharina from U.S. and Laminaria digitata from Iceland also have close M/G ratio. However, the concentrations of alginate solutions extracted from all these six brown seaweeds are not high enough compared with the alginate standard solution, thus the oligosaccharides are not successfully detected in the LC-MS/MS study. Therefore, more efficient and optimal extraction methods should be further explored to extract sufficient alginates for the analysis of the chemical structure, bioactive function as well as regional difference.