Heparin sodium compliance to the new proposed USP monograph: Elucidation of a minor structural modification responsible for a process dependent 2.10 ppm NMR signal

Heparin is a highly sulfated hetero polysaccharide mixture found and extracted from mammalian tissues. It has been widely used as an anticoagulant drug during the past decades.In the new proposed USP heparin monograph, the 1H NMR acceptance criteria to prevent contamination by over sulfated chondroitin sulfate (OSCS), or other persulfated glycosaminoglycans, specifies that no unidentified signals greater than 4% of the mean of signal height of 1 and 2 [1] should be present in the following ranges: 0.10–2.00, 2.10–3.20, and 5.70–8.00 ppm. However, those criteria do not take into account the impact of potential structural modifications generated by the heparin manufacturing processes. In fact, starting from pig mucosa, heparin purification involves oxidizing reagents such as sodium peroxide, potassium permanganate and peracetic acid. In the present work, we demonstrate that potassium permanganate treated heparins show a small but characteristic extra signal at 2.10 ppm. Controlled heparinase I depolymerisation is used to target and excise the oligosaccharide responsible for this extra signal from the polysaccharide backbone. By using orthogonal chromatographic techniques, the fingerprint oligosaccharide was isolated and its structure elucidated. Without the identification of this structural moiety, such purified heparins may have been considered as non-compliant drug substance and not suitable for pharmaceutical use.