Alginic acid

Absorption

The absorption into the systemic circulation from oral formulations of alginic acid is reported to be minimal, as the mode of action of alginic acid is physical .

Toxicity

Probable oral lethal dose reported in humans is above 15 g/kg . Ingestion of large quantities may result in abdominal distension, intestinal obstruction, nausea, vomiting, and difficulty swallowing. Aspiration or inhalation may lead to pneumonitis . In the event of overdosage symptomatic treatment should be given .

Chemical properties

Alginic acid is a tasteless, practically odorless, white to yellowishwhite, fibrous powder.

Chemical properties

Alginic acid found in the walls of brown seaweeds (Phaeophyceae) consists of D-mannuronic acid units and L-guluronic acid units probably linked β (1->4). The chains contain three distinct regions; in one, the D-mannuronic acid units alternate with L-guluronic acid units, whereas the remaining regions are homogeneous and contain either D-mannuronic acid or L-guluronic acid. The lengths and proportions of the three regions vary with the seaweed species and are responsible for the differences in chemical and physical properties of the various alginates.
Alginic acid is biosynthesised from GDP-D-mannuronic acid and GDP-guluronic acid. It seems probable that guluronic acid is derived from its isomer, mannuronic acid, the re action being catalysed by an epimerase.

Monovalent salts of alginic acid are soluble in water, but polyvalent salts are either insoluble or form gels. Solutions of alginates are very viscous due to the high molecular weight and random-coil formation of the polymers. The jellying and thickening properties of alginates are widely used commercially in foodstuffs, etc.

The Uses of Alginic acid

algin (alginic acid) is used in cosmetic formulations as a thickener, stabilizer, and gelling agent. It is obtained from different varieties of brown seaweed.

The Uses of Alginic acid

corrosive moisture sensitive

The Uses of Alginic acid

Alginic Acid is the acidic, insoluble form of algin that is a white to yellowish fibrous powder obtained from brown seaweed genera, such as macrocystis pyrifera. the derivatives are soluble and include sodium, potassium, and ammonium alginate and propylene glycol alginate. it is used as a tablet disintegrant and as an antacid ingredient.

The Uses of Alginic acid

Gum derived from alginic acid which is obtained from brown seaweed genera, such as Macrocystis pyrifera. The derivatives are sodium, ammonium, and potassium ates of which the sodium salt is most common. They are used to provide thickening, gelling, and binding. A derivative designed for improved acid and calcium stability is propylene glycol ate. The s are soluble in cold water and form nonthermoreversible gels in reaction with calcium ions and under acidic conditions. Algin is used in ice cream, icings, puddings, dessert gels, and fabricated fruit.

Background

Alginic acid, also referred to as algin or alginate, is a hydrophilic or anionic polysaccharide isolated from certain brown seaweed (Phacophycae) via alkaline extraction. It is present in cell walls of brown algae where it forms a viscous gel when binding with water. Alginic acid is a linear polymer consisted of L-glucuronic acid and D-mannuronic acid residues connected via 1,4-glycosidic linkages . Available in different types of salt, alginic acid has been used in a variety of uses in food, cosmetics and pharmaceu-tical products for over 100 years . Alginic acid is an FDA-approved food ingredient in soup and soup mixes as an emulsifier, thickener, and stabilizer . It is also available in oral dietary supplements and is found in antacids such as Gaviscon to inhibit gastroesophageal reflux by creating a physical barrier in presence of gastric acid . Alginate-based raft-forming formulations in the management of heartburn and gastric acid reflux have been used worldwide for over 30 years .

Indications

Indicated for the management of gastric reflux, reflux oesophagitis, hiatus hernia, heartburn (including heartburn of pregnancy) and similar gastric distress .

Definition

A polysaccharide composed of β,d-mannuronic acid residues linked so that the carboxyl group of each unit is free, while the aldehyde group is shielded by a glycosidic linkage. It is a linear polymer of the mannuronic acid in the pyranose ring form.

Production Methods

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.

Definition

A yellow-white organic solid that is found in brown algae. It is a complex polysaccharide and produces, in even very dilute solutions, a viscous liquid. Alginic acid has various uses, especially in the food industry as a stabilizer and texture agent.

Pharmaceutical Applications

Alginic acid is used in a variety of oral and topical pharmaceutical formulations. In tablet and capsule formulations, alginic acid is used as both a binder and disintegrating agent at concentrations of 1–5% w/w. Alginic acid is widely used as a thickening and suspending agent in a variety of pastes, creams, and gels; and as a stabilizing agent for oil-in-water emulsions.
Alginic acid has been used to improve the stability of levosimendan.
Therapeutically, alginic acid has been used as an antacid.In combination with an H2-receptor antagonist, it has also been utilized for the management of gastroesophageal reflux.

Pharmacokinetics

Alginic acid reduces reflux via its floating, foaming, and viscous properties . Alginic acid precipitates upon contact with gastric acid to create a mechanical barrier, or a "raft", that displaces the postprandial acid pocket . The formation of a raft is thought to occur rapidly, often within a few seconds of dosing . In clinical trials, alginic acid was effective in reducing the symptoms of gastroesophageal reflux disease (GERD) . In healthy volunteers, alginic acid in combination with an antacid was effective in decreasing postprandial reflux in the upright position . Alginic acid is able to bind to cations when ingested .

Safety Profile

Moderately toxic by intraperitoneal route. When heated to decomposition it emits acrid smoke and irritating fumes

Safety

Alginic acid is widely used in food products and topical and oral pharmaceutical formulations. It is generally regarded as a nontoxic and nonirritant material, although excessive oral consumption may be harmful. Inhalation of alginate dust may be an irritant and has been associated with industrially related asthma in workers involved in alginate production. However, it appears that the cases of asthma were linked to exposure to unprocessed seaweed dust rather than pure alginate dust. An acceptable daily intake of alginic acid and its ammonium, calcium, potassium, and sodium salts was not set by the WHO because the quantities used, and the background levels in food, did not represent a hazard to health.
LD₅₀ (rat, IP): 1.6 g/kg

Metabolism

This pharmacokinetic parameter is unlikely to apply for alginic acid.

storage

Alginic acid hydrolyzes slowly at warm temperatures producing a material with a lower molecular weight and lower dispersion viscosity.
Alginic acid dispersions are susceptible to microbial spoilage on storage, which may result in some depolymerization and hence a decrease in viscosity. Dispersions should therefore be preserved with an antimicrobial preservative such as benzoic acid; potassium sorbate; sodium benzoate; sorbic acid; or paraben. Concentrations of 0.1–0.2% are usually used.
Alginic acid dispersions may be sterilized by autoclaving or filtration through a 0.22 μm filter. Autoclaving may result in a decrease in viscosity which can vary depending upon the nature of any other substances present.
Alginic acid should be stored in a well-closed container in a cool, dry place.

Purification Methods

To 5g of acid in 550mL water containing 2.8g KHCO3 are added 0.3mL of acetic acid and 5g potassium acetate. EtOH is added to make the solution to 25% (v/v) in EtOH, and any insoluble material is discarded. Further addition of EtOH, to 37% (v/v), precipitated alginic acid. Collect the acid and dry it in vacuo. [Pal & Schubert J Am Chem Soc 84 4384 1962.]

Incompatibilities

Incompatible with strong oxidizing agents; alginic acid forms insoluble salts in the presence of alkaline earth metals and group III metals with the exception of magnesium.

Regulatory Status

GRAS listed. Accepted in Europe for use as a food additive. Included in the FDA Inactive Ingredients Database (ophthalmic preparations, oral capsules, and tablets). Included in the Canadian List of Acceptable Non-medicinal Ingredients. Included in nonparenteral medicines licensed in the UK.