Alginic acid
[CAS# 9005-32-7]

Identification

• Classification: Biochemical >> Plant extracts
• Name: Alginic acid
• Synonyms: Alginic acid from Macrocystis pyrifera (kelp); Mixed polymer of mannuronic and guluronic acid
• Molecular Formula: (C₁₂H₁₆O₁₂)_n
• CAS Registry Number: 9005-32-7
• EC Number: 232-680-1
• SMILES: CO[C@H]1[C@H](O)[C@H](O)[C@H](O[C@H]2[C@H](O)[C@H](O)[C@H](C)O[C@@H]2C(=O)O)O[C@H]1C(=O)O

Properties

• Melting point: 300 ºC
• Water solubility: insoluble

Discovory and Applicatios

Alginic acid is a naturally occurring polysaccharide that is primarily found in the cell walls of brown algae. It is composed of repeating units of mannuronic acid and guluronic acid, which are linked through β-1,4-glycosidic bonds. Alginic acid was first isolated from brown seaweed in the 19th century, with the work of British chemist Edward C. C. Stanford in 1881 leading to its formal identification. Since then, alginic acid has become a widely studied substance due to its diverse applications in various industries, ranging from food to pharmaceuticals.

The primary source of alginic acid is brown algae, especially the genera *Laminaria*, *Ascophyllum*, and *Macrocystis*, which are rich in alginates. Alginic acid is often extracted from these algae through a process that involves treating the seaweed with alkali to obtain sodium alginate, which is subsequently converted to alginic acid. Alginic acid is typically available as a white to light brown powder, and its composition varies depending on the source and extraction method.

In the food industry, alginic acid and its salts, particularly sodium alginate, are used as thickening agents, stabilizers, and gelling agents. Sodium alginate is commonly employed in the production of gels, especially in the preparation of products such as jelly, gummy candies, and ice cream. It is also used to stabilize emulsions in products like salad dressings and sauces, as well as to prevent crystallization in ice cream and other frozen desserts. Alginic acid's ability to form gels in the presence of calcium ions makes it a valuable component in the food industry, particularly for creating textures in foods that are desirable for consumers.

In pharmaceuticals, alginic acid is used as an excipient in the formulation of various oral and topical products. As a pharmaceutical excipient, alginic acid serves as a binder, stabilizer, and controlled-release agent. It is commonly used in the production of tablets, capsules, and oral suspensions, where it helps improve the consistency and stability of the formulation. Alginic acid is also used in the production of antacid preparations, as it forms a gel-like barrier in the stomach that can help reduce acid reflux. Additionally, alginic acid is used in wound care products, such as dressings for burns and other skin injuries, where it provides a moist environment conducive to healing.

Alginic acid has applications in the textile and paper industries, where it serves as a sizing agent, helping to enhance the durability and smoothness of paper and fabric. In the textile industry, it is used in the preparation of fabrics, where it can improve the fabric's ability to hold dyes and prevent color bleeding. In the paper industry, alginic acid is used to improve the paper's strength and reduce its porosity, which is beneficial in the production of high-quality paper products.

In the biomedical field, alginic acid is utilized in tissue engineering and drug delivery systems. Due to its biocompatibility, biodegradability, and ability to form gels, alginic acid is used in the development of scaffolds for tissue regeneration. These scaffolds can support cell growth and help repair damaged tissues. Alginic acid is also employed in drug delivery applications, where it is used as a carrier for controlled release of active pharmaceutical ingredients. This ability to form hydrogels that can encapsulate and release drugs in a controlled manner is of significant interest in developing sustained-release formulations for medications.

Alginic acid is also used in the production of biodegradable plastics and films. Due to its natural origin and biodegradability, alginic acid is a suitable material for producing eco-friendly packaging materials. This application has gained attention as part of the broader effort to reduce the environmental impact of plastic waste.

Beyond these applications, alginic acid is used in cosmetics and personal care products, where it functions as a thickener, emulsifier, and moisturizer. It is found in formulations such as lotions, creams, shampoos, and facial masks, contributing to the product's texture and stability.

Alginic acid's diverse range of applications is largely attributed to its unique chemical structure, which allows it to form gels, thicken liquids, and interact with other materials in a wide variety of ways. As a result, alginic acid remains an important substance in a variety of industries, from food and pharmaceuticals to biomedicine and environmental applications.

References

2022. Alginic acid induces oxidative stress-mediated hormone secretion disorder, apoptosis and autophagy in mouse granulosa cells and ovaries. Toxicology, 467.
DOI: 10.1016/j.tox.2022.153099

2008. Development of polyvinyl alcohol-sodium alginate gel-matrix-based wound dressing system containing nitrofurazone. International Journal of Pharmaceutics, 359(1-2).
DOI: 10.1016/j.ijpharm.2008.03.021

2003. Modulation of TNF-α-induced ICAM-1 expression, NO and H2O2 production by alginate, allicin and ascorbic acid in human endothelial cells. Archives of Pharmacal Research, 26(3).
DOI: 10.1007/bf02976837