Chemical effects of UV radiation on aqueous solutions of heparin-Ca salt

Abstract

Chemical effects of 184·9 nm, 194·2 nm and 253·7 nm ultraviolet radiation on dilute aqueous solutions of heparin-Ca salt are investigated. The degradation of heparin in dilute aqueous solutions involves two different mechanisms: (a) at 184·9 nm, an H^• abstraction process takes place: and (b) at 194·2 nm and 253·7 nm, heparin free radicals formed due to glycosidic bond dissociation are involved. These mechanisms are responsible for the depolymerisation of heparin molecules. The presence of sulphate groups renders stability to heparin, which requires long exposure to ultraviolet radiation to produce metachromasia in the cationic dye Acridine Orange, and changes in reducing-end group, hexuronic acid and hexosamine moieties in the presence of oxygen or nitrogen. The effects of three wavelengths and the existence of two degradation pathways are discussed.