Chondroitin sulfate belongs to a family of heteropolysaccharides called glycosaminoglycans or GAGs. Glycosaminoglycans were formerly known as mucopolysaccharides. GAGs in the form of proteoglycans comprise the ground substance in the extracellular matrix of connective tissue. Chondroitin sulfate is made up of linear repeating units containing D-galactosamine and D-glucuronic acid. Chondroitin sulfate is found in humans in cartilage, bone, cornea, skin and the arterial wall. This type of chondroitin sulfate is sometimes referred to as chondroitin sulfate A or galactosaminoglucuronoglycan sulfate. The amino group of galactosamines in the basic unit of chondroitin sulfate A is acetylated, yielding N-acetyl-galactosamine; there is a sulfate group esterified to the 4-position in N-acetyl-galactosamine. (Chondroitin sulfate A is also sometimes called chondroitin 4-sulfate.) The molecular weight of chondroitin sulfate ranges from 5,000 to 50,000 daltons and contains about 15 to 150 basic units of D-galactosamine and D-glucuronic acid. It is represented by the following structural formula:
Chondroitin sulfate A R = SO3H R1 = H
Chondroitin sulfate C R = H R1 = SO3H
Chondroitin sulfate C, primarily found in fish and shark cartilage, but also in humans, is also made up of linear repeating units of D-galactosamine and D-glucuronic acid. The amino group of D-galactosamine is acetylated to give N-acetyl-galactosamine, and, in the case of chondroitin sulfate C, the sulfate group is esterified to the 6-position in N-acetyl-galactosamine. Chondroitin sulfate C is sometimes called chondroitin 6-sulfate. Chondroitin sulfate B is also known as dermatan sulfate. It is abundant in skin and is also found in heart valves, tendons and arterial walls. Dermatan sulfate is made up of linear repeating units containing D-galactosamine and either L-iduronic acid or D-glucuronic acid. Its molecular weight ranges from 15,000 to 40,000 daltons.
The source of chondroitin sulfate used in nutritional supplements includes the cartilaginous rings of bovine trachea and pork byproducts (ears and snout). Shark cartilage and whale septum cartilage have also been used to obtain chondroitin sulfate. Chondroitin sulfate supplements are usually isomeric mixtures of chondroitin sulfate A(chondroitin 4-sulfate) and chondroitin sulfate C(chondroitin 6-sulfate).