Figure 1: Di- and tetrasaccharide repeating units of the most important natural GAGs. In dependence on the biological source of the GAGs, structural variations may occur to a minor extent (e.g. differences of the sulfation patterns) in low-sulfated GAGs (CS, DS, KS) but to a larger extent (variations of monosaccharides in the repeating unit) in high-sulfated HE and HS. The “free” acids are given in all cases although the occurrence of the corresponding (sodium) salts is much more probable at physiological conditions. Please note that the different commercially available CS preparations are sorted according to their sulfation patterns.