Chondroitin sulfate is an amino sugar polymer, made up of glucuronic acid and galactosamine, that is in the class of large polymers known as glucosaminoglycans or mucopolysaccharides. These compounds act as the flexible connecting matrix between the protein filaments in cartilage and connective tissue (Liesegang 1990). Chondroitin is manufactured from natural sources, such as shark and bovine (usually tracheal) cartilage and may have a molecular weight that varies from 10 to 50 kD, depending on the product's source or preparation (Ross 2000).
There are differences in the absorption and bioavailability of chondroitin formulations due to differences in molecular mass, charge density, and cluster of disulfated disaccharides of the parental molecules (Volpi 2003). Low-molecular-weight chondroitin appears to be absorbed orally in both animals and humans (Adebowale et al 2002, Du et al 2004) and displays accumulation after multiple dosing (Adebowale et al 2002).
Chondroitin is concentrated in the intestine, liver, kidneys, synovial fluid and cartilage (Conte et al 1995) and the elimination half-life is about 5-6 hours, with 40-50% being excreted in the urine (Conte et al 1991, Ronca & Conte 1993). Oral chondroitin is absorbed as several metabolites, and as the active moiety has not yet been identified it is difficult to establish bioequivalence between different products (Volpi 2003).
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