Mechanism of radioprotection by beta-aminoethylisothiouronium bromide hydrobromide

beta -Aminoethylisothiouronium bromide hydrobromide (AET) undergoes tautome ric conversion to mercaptoethylguinidine (MEG) through a transient product in aqueous solution. This conversion is facilitated by increase of pH, conc entration of AET and radiation dose upto 2.5 Gy. Analytical evidences indic ate radiation protection mechanism offered by AET is due to formation of ME G and subsequent neutral radiolytic products. So long as these products con tain SH and NH2 groups separated by 2-3 carbon atoms, they are able to scav enge OH. radicals by proton donation from SII groups and absorption of H+ i ons by NH2 groups. These sulfydryl compounds may block the peroxidation pro cess by reacting with free radicals in competition with oxygen and may rest ore it to its original state.