Chondroitin sulfate (CS) is a type of glycosaminoglycan that is covalently linked to proteins to form proteoglycans. Chondroitin sulfate is widely distributed in the extracellular matrix and cell surface of animal tissues. The sugar chains are polymerized by alternating glucuronic acid and N-acetylgalactosamine, and are connected to the serine residues of the core protein through a sugar-like linking region. .

Although the main chain structure of polysaccharides is not complicated, it presents a high degree of inhomogeneity in terms of the degree of sulfation, sulfate groups, and the distribution of the two differences into the chain of isomerized uronic acid. The fine structure of chondroitin sulfate determines the specificity of function and the interaction with a variety of protein molecules.