Radioprotective thermally generated free-radical dextrins

Effect of doses of the X-ray radiation from 0 to 400 Gy upon granular cornstarch and dextrins (British gums, BG) thermally generated from it at 230–300°C was recognized with quantitative EPR and IR absorption spectroscopy, molecular mass distribution in the depolymerization products, Scanning Electron Microscopy, and X-ray diffractometry. Fractal analysis of the profiles of molecular mass distribution showed that the depolymerization involved debranching of amylopectin. Roasting of cornstarch produced BG which differed in concentration and EPR parameters of stable free radicals from BG generated by X-ray radiation. Two types of stable free radicals, with Gaussian and Lorentzian shapes of EPR signals, were recognized. The shapes of the signals and temperature dependence on free radical intensity indicated exchanging interactions of the antiferromagnetic type, causing partial quenching of the spins at 196°C (77K). Upon X-ray irradiation, new radicals were generated, the number and stability of which strongly depended on the types of radicals present before irradiation. These radicals slowly ceased because of a repolymerization of BG on storage. Supported by the Polish Ministry of Science and Informatics (Grant Nos. 2 PO6T 087 27 (E.B., K.D.) and PBZ-KBN 070/T09/2001 (P.T., O.M., M.F.))