Seaweeds, brown —, alginic acid

Algin occurs in all members of the class Phaeophjceae, brown seaweed, as a stmctural component of the cell walls in the form of the insoluble mixed calcium, magnesium, sodium, and potassium salt of alginic acid. 

Alginic acid is a hydrophilic colloid carbohydrate that occurs naturally in the cell walls and intercellular spaces of various species of brown seaweed (Phaeophyceae). The seaweed occurs widely throughout the world and is harvested, crushed, and treated with dilute alkali to extract the alginic acid. 

Alginate obtained from brown seaweed is subjected to demineralization, extraction, and precipitation of alginic acid. Following neutralization, the potassium alginate obtained is dried and milled. 

Alginic acid is extracted from brown seaweed and is neutralized with sodium bicarbonate to form sodium alginate. 

Derivation Extracted from brown seaweeds (alginic acid). 

All processes so far published for the production of alginic acid or its salts from the brown marine algae are variants of that initially described by Stanford (lS-15), The seaweed is first washed with water or acid to remove the soluble constituents and then digested with dilute aqueous sodium carbonate solution to give a dilute solution of crude sodium alginate which, after separation from the insoluble weed constituents, is acidified and the alginic acid thus precipitated is washed, pressed, and dried. 

Antioxidant. Sulfated polysaccharides not only function as dietary fiber, but they also contribute to the antioxidant activity of seaweeds. It has been demonstrated that they exhibit potential antioxidant activity in vitro and several of them derived from brown seaweeds, such as fucoidan, laminaran, and alginic acid, have been shown as potent antioxidants (Rocha De Souza et ah, 2007 Ruperez et ah, 2002 Wang et ah, 2008, 2010). 

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