CONICET | Buscador de Institutos y Recursos Humanos

Kinetic studies show that the redox reaction proceeds through a mechanism combining CrVI CrIV CrII and CrVI CrIV CrIII pathways. The mechanism is supported by the observation of free radicals, CrO22+ (the formation of which implies involvement of CrII and CrIV) and CrV (formed in monoelectronic redox processes) as reaction intermediates. The reduction of CrIV and CrV by pectin was independently studied and found to occur more than 103 times faster than pectin + CrVI reaction, in acid medium. At pH 3-5, apple pectin + CrVI redox reaction is slow, oxo-chromate(V)-pectin species stabilize and remain in solution during several hours. The present results show that these abundant and ubiquitous components of the cell walls of all land plants are able to reduce CrIV-VI or stabilize high-valent chromium depending on pH.VI CrIV CrII and CrVI CrIV CrIII pathways. The mechanism is supported by the observation of free radicals, CrO22+ (the formation of which implies involvement of CrII and CrIV) and CrV (formed in monoelectronic redox processes) as reaction intermediates. The reduction of CrIV and CrV by pectin was independently studied and found to occur more than 103 times faster than pectin + CrVI reaction, in acid medium. At pH 3-5, apple pectin + CrVI redox reaction is slow, oxo-chromate(V)-pectin species stabilize and remain in solution during several hours. The present results show that these abundant and ubiquitous components of the cell walls of all land plants are able to reduce CrIV-VI or stabilize high-valent chromium depending on pH.