Transient Intermediates in the Radiolysis of Hyaluronic Acid

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Abstract
By means of electron paramagnetic resonance (EPR) after gamma-irradiation in the solid state, hyaluronic acid, glucuronic acid, and N-acetylglucosamine were found to have the following G (radicals), respectively: 3.7, 2.6, and 3.8. The EPR spectra of hyaluronic acid (at low dose) showed a doublet with hyperfine splitting of 4 to 5 gauss. Glucuronic acid after irradiation gave only a single which could not be further resolved. The intermediates satisfactorily account for the observed chemical degradation and EPR data. Pulse radiolysis of aqueous solutions, with 4-MeV electons, showed that eaq and OH radicals react rapidly with hyaluronic acid (HA), and the following rate constants (based on disaccharide repeating unit concentration) were found: eaq + HA [forward arrow] k2 = 3 to 8 x 108 M-lsec-1; OH + HA [forward arrow] k2 = 8 [plus or minus] 0.4 x 108 M-1 sec-l. The susceptibility of hyaluronic acid to radiation damage is thus due to reaction with both major products of water radiolysis. In the solid state, hyaluronic acid similarly to other polysaccharides on gamma-irradiation.

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