Abstract:
Ecklonia maxima is an endemic South African
seaweed with numerous commercially valuable compounds,
including sodium alginate. This polysaccharide contains
1,4-linked β-D-mannuronic (M) and α-L-guluronic acid
(G) residues, and has enormous health and food applications
and benefits for biomedicine. In this study, acid extraction of
sodium alginate from Ecklonia maxima was performed, and
its chemical and physical properties were compared with
commercial sodium alginate. A yield of 58.7 % (w/w of dry
alga) sodium alginate was recovered from the seaweed.
As expected, Fourier-transform infrared spectroscopy and
nuclear magnetic resonance spectroscopic analyses of
sodium alginate revealed the presence of M and G residues
in the polysaccharide. Circular dichroism (CD) spectroscopy
revealed an M/G ratio of 1.86 from the extracted sodium
alginate. The viscosity average molecular weight of sodium
alginate was 429 kDa using the Mark–Houwink–Sakurada
equation. Three-dimensional conformational analysis by
Congo red and CD spectroscopy suggested that sodium
alginate exhibits a triple-helix conformation in solution.
Furthermore, X-ray powder diffraction analysis confirmed
that the alginate has an amorphous structure. Sodium
alginate extracted from E. maxima found on the coasts of
Southern Africa exhibits a high mannuronic content and
high viscosity, potentially beneficial for drug delivery and
biomedical applications.
