Sodium alginate is a byproduct of extracting iodine and mannitol from kelp or giant kelp of brown algae. Its molecule is composed of β-D-mannuronic acid (β-D-mannuronic, M) and α-L-guluronic acid (α-L-guluronic, G) connected by (1→4) bonds. It is a natural polysaccharide with the stability, solubility, viscosity and safety required for pharmaceutical excipients. It was first described in a patent application filed by British chemist Edward CC Stanford in 1881. Sodium alginate is the sodium salt of alginate, and its empirical formula is (C6H7O6Na)n. The physical characteristics of sodium alginate are powder or fiber form, white to slightly yellow, almost tasteless and odorless. To date, brown algae is still the main source from which sodium alginate is extracted.
