Glucosamine and chondroitin sulfate are both substances that are found naturally in the body. A glucosamine molecule is formed by adding an amino group (NH2) to a glucose molecule, thereby creating an amino sugar. Glucosamine is a component of a number of structures in the body and is believed to play a role in the formation and repair of cartilage.
Chondroitin sulfate is a member of a class of large molecules called sulfated glycosaminoglycans; these molecules contain sugars, proteins, and sulfur. Chondroitin sulfate is a major constituent in various connective tissues, as well as bone, and cartilage. It is thought to impart elasticity to cartilage.
Both glucosamine and chondroitin sulfate are sold as nutritional supplements. Manufacturers of these supplements extract their raw materials from animal tissue. For example, glucosamine can be extracted from the shells of shrimp, lobsters, or crabs, while chondroitin sulfate can be removed from the cartilage of animals, such as sharks.