ANODIC BEHAVIOR OF SOME VINCA ALKALOIDS WITH CYTOSTATIC ACTIVITY - EFFECT OF PH

The anodic oxidation mechanism of the Vinca alkaloids vinblastine, its semisynthetic derivatives vindesine and 5'-noranhydrovinblastine, and of vincristine, all with closely similar structures, was studied at a glassy carbon disk electrode in buffered aqueous media using differen tial pulse and cyclic voltammetry. The effect of pH on the mechanism s howed that it is a complex multistep electron transfer with deprotonat ion steps involved and that the final products, dimers or polymers, ad sorb strongly to the electrode, forming an unreactive film on the elec trode surface. The electrochemical differential pulse voltammograms sh owed a correlation between the vinblastine derivatives, whereas vincri stine reacts at different potentials. These differences in the anodic oxidation mechanisms of the compounds studied can be related to their neurotoxicity and myelosuppression effects. These effects may be due t o the metabolite and/or degradation products of the compounds and resu lt from how they are attached to, or transported across, cellular stru ctures such as cell membranes.