GENERATION OF ACETYL FREE-RADICALS BY RADIOLYSIS - COMPARISON OF FREE-RADICALS GENERATED FROM ACETALDEHYDE AND ETHYLENE-GLYCOL

Taking into account that acetaldehyde is toxic towards some cellular components (specifically enzymes), it appears of great interest for biologists to produce the acetyl radical from a less toxic precursor in order to distinguish the reactivity of this radical from acetaldehyde toxicity. It was shown previously that acetaldehyde, after reaction with the OH. radical, produces acetyl and formylmethyl radicals, whereas it was imputed that the radical produced from ethylene-glycol, under the same conditions, is the formylmethyl radical. As the acetyl and formylmethyl radicals can be considered as tautomeric forms, we postulate that it could be possible to obtain, by radiolysis under an atmosphere of N2O and at neutral pH, the same species from ethylene-glycol than from acetaldehyde. Thus the optical absorption spectra of the intermediates obtained by pulse radiolysis of N2O-saturated solutions of acetaldehyde or ethylene-glycol and the kinetics of their decays have been investigated. The primary species obtained by the reaction of the OH. radical with ethylene-glycol disappears with k = 1.5 x 10(5) s-1 and gives another transient which is also observed during pulse radiolysis of acetaldehyde. This latter transient disappears with 2k = 1.5 x 10(8) mol-1.1.s-1. These results suggest that the OH. radical reactions with acetaldehyde or ethylene-glycol produce acetyl and formylmethyl radicals. Besides, these radicals are shown to reduce ferricytochrome c (k = 3 x 10(6) mol-1.l.s-1) with G(max) (- cyt c-Fc3+) congruent-to G(OH.) = 5.6 x 10(-7) mol.J-1.