Coupling Liquid Chromatography and Tandem Mass Spectrometry to Electrophoresis for In-Depth Analysis of Glycosaminoglycan Drugs: Heparin and the Multicomponent Sulodexide

Glycosaminoglycans (GAGs) contribute to the treatment of many human diseases, especially in the field of thrombosis, because of their anticoagulant activity. GAGs interrupt the coagulation process by interacting with multiple coagulation factors through defined sequences within their linear and negatively charged chains, which are not fully elucidated. Numerous methods have been developed to characterize the structure of pharmaceutical GAGs, including intravenously or subcutaneously administered heparin and orally administered sulodexide. However, most currently available methods only focus on the oligosaccharide portion or analyze the whole mixture because longer-chain polysaccharides are extremely difficult to resolve by chromatographic separation. We have established two novel electrophoresis-mass spectrometry methods to provide a panoramic view of the structures of pharmaceutical GAGs. In the first method, an in-gel digestion procedure was developed to recover GAGs from the polyacrylamide gels, while in the second method, a strong anion exchange ultrafiltration procedure was developed to extract multiple GAG species from the agarose gels. Both procedures are compatible with liquid chromatography-tandem mass spectrometry, and structural information, such as disaccharide composition and chain length, can be revealed for each GAG fraction. The applications of these two methods on analysis of two different GAG drugs, heparin and sulodexide, were demonstrated. The current study offers the first robust tool to directly elucidate the structure of larger GAG chains with more biological importance rather than obtaining a vague picture of all chains as a mixture, which is fundamental for better understanding the structure-activity relationship and quality control of the GAG drugs.