1H and 13C nuclear magnetic resonance identification and characterization of components of chondroitin sulfates of various origin

Three natural chondroitin sulfates (CSs), from porcine and bovine trachea, and from shark cartilage, were studied using a variety of NMR techniques (DQS, TOCSY, NOESY, HMQC). A good 1H and 13C characterization of the major components, chondroitin 4-sulfate (CS4) and chondroitin 6-sulfate (CS6), was obtained and a number of signals coming from chondroitin 2,6-disulfate (CS2,6) (present only in shark CS) was identified. The study of a chemically desulfated CS was necessary in order to understand the difficulties encountered in detecting signals from the chondroitin nonsulfate (CS0) component of porcine and bovine CSs. The singular pattern of UC-4 and NC-1 signals was recognized and explained in terms of a diad model. The "excess of multiplicity" affecting mainly these two signals was attributed to the differences in the conformation of the N 1:4 U glycosidic bond. Further support to this hypothesis comes from the comparison of the NOESY spectra of the three CSs.