Chemical change involved in the oxidative-reductive depolymerization of heparin

Area of Science:

• Biochemistry
• Polymer Chemistry
• Pharmacology

Background:

• Heparin is a complex polysaccharide with significant anticoagulant properties.
• Understanding heparin's depolymerization mechanisms is crucial for developing modified heparin derivatives.

Purpose of the Study:

• To investigate the chemical and structural changes in heparin during oxidative-reductive depolymerization (ORD).
• To elucidate the specific mechanisms and vulnerable sites involved in heparin degradation.

Main Methods:

• Incubation of hog intestinal heparin with Fe2+ under an oxygen atmosphere at 50°C.
• Chemical analysis to quantify hexosamine, uronic acid, and N-acetyl groups.
• 1H and 13C NMR spectroscopy to analyze uronic acid composition and sulfation patterns.

Main Results:

• ORD heparin exhibited reduced molecular weight and anticoagulant activity.
• Significant losses in hexosamine, uronic acid, and N-acetyl groups were observed.
• NMR analysis revealed a marked loss of nonsulfated D-glucuronic and L-iduronic acids, while L-iduronic acid 2-sulfate remained largely intact.

Conclusions:

• The ORD reaction of heparin primarily involves the destruction of monosaccharide units, particularly nonsulfated uronic acids, by oxygen-derived free radicals.
• Secondary hydrolytic cleavage of the resulting unstable residues contributes to the overall depolymerization process.
• The selective preservation of L-iduronic acid 2-sulfate residues suggests a specific resistance mechanism or a different degradation pathway for these units.