Profiling sulfate content of polysaccharides in seaweed species using a ligand-assisted ¹H-NMR assay

This study aimed to use an existing ligand (imidazole)-assisted 1H-nuclear magnetic resonance (1H-NMR) spectroscopy protocol determine sulfate content of seaweed sulfated saccharides. Twenty samples – spanning nine species and multiple geographic locations were analyzed. Extracts obtained by immersing freeze-dried seaweeds in boiling water, followed alginate precipitation. Remaining supernatants contained natural crude polysaccharide (CP) fraction, including polysaccharides. To eliminate free CP carboxy groups that can interfere with the complex formation imidazole groups, chemically reduced hydroxymethyl prior 1H-NMR spectroscopy. Resultant estimates comparable those via a conventional barium-rhodizonate assay. Findings indicate imidazole-assisted is appropriate method for estimation content.