The mediation of veratryl alcohol in oxidations promoted by lignin peroxidase: the lifetime of veratryl alcohol radical cation

The kinetics of decay of veratryl alcohol radical cation, generated by cerium(IV) ammonium nitrate induced oxidation of veratryl alcohol, have been followed spectrophotometrically in a stopped-flow apparatus. In acidic aqueous acetonitrile the radical cation was found to decay by a first-order process, due to deprotonation from the a-carbon leading to an a-hydroxybenzyl radical with the rate constant of 17.1 +/- 0.5 s(-1). This value is in full agreement with those obtained by pulse radiolysis studies but much lower than the value (1.2 x 10(3)s(-1)) indirectly determined by EPR experiments. The implications of these results with respect to the possible role of veratryl alcohol as a mediator in the oxidative biodegradation of lignin catalysed by lignin peroxidase are discussed. (C) 2002 Elsevier Science (USA). All rights reserved.