Chitin, Chitosan, and Chitooligosaccharide (COS) are three related compounds with distinct characteristics and properties.
Chitin, discovered in 1811 by French scholar Braqueno, is extracted from crustacean shells. It appears as a light beige to white substance. Insoluble in water, alkali, common acids, and organic solvents, chitin can only be dissolved in concentrated acids. It is partially decomposed by chitinase and lysozyme in the human gastrointestinal tract.
Chitosan, derived from chitin through chemical treatment that removes the acetyl group, is soluble in dilute acid, making it more versatile than chitin. Both chitin and chitosan are macromolecules with molecular weights ranging from hundreds of thousands to millions, and they are insoluble in water.
Chitooligosaccharide (COS), on the other hand, is obtained by degrading chitosan into smaller molecules. With a molecular weight of about 3000Da and a degree of polymerization of 2-20, COS is a mixture containing monosaccharides up to chitosan, each with its own specific functionality. COS can be easily dissolved in water, with a water solubility exceeding 99%, and it has a high absorption rate in the human body.
The specific differences between chitosan and COS are as follows:
1. Molecular weight: COS has a molecular weight below 3000Da, while chitosan has a molecular weight of 500,000-1,000,000.
2. Solubility: COS has a lower molecular weight and is completely soluble in water, whereas chitosan can only be dissolved in dilute acid solutions. The water solubility of COS is crucial for its physiological activities, as it allows for absorption and utilization by organisms.
3. Functionality: COS with a molecular weight below 2000Da exhibits unique physiological activities such as improving macrophage function, inhibiting tumor cell growth and metastasis, reducing cholesterol and blood lipids, and displaying antibacterial and moisture absorption capabilities.
Oligochitosan, with a molecular weight below 5000Da, can hinder the growth and reproduction of pathogenic bacteria, promote protein synthesis, activate plant cells, and stimulate rapid plant growth.
Chitosan oligosaccharides are highly valuable in the oligosaccharide family due to their various functions. They are the only alkaline and positively charged oligosaccharides, allowing for absorption in the intestinal tract and distribution throughout the body. To ensure intestinal absorption, chitosan oligosaccharides must resist digestion by digestive enzymes. Their unique structure, with glucosamine linked by β-1,4-glycosidic bonds, enables them to maintain structural integrity in the gastrointestinal tract.