THE INTERACTION OF MELATONIN AND ITS PRECURSORS WITH ALUMINUM, CADMIUM, COPPER, IRON, LEAD, AND ZINC - AN ADSORPTIVE VOLTAMMETRIC STUDY

Melatonin, a pineal secretory product, and its precursors, tryptophan and serotonin, were examined for their metal binding affinities for bo th essential and toxic metals: aluminium, cadmium, copper, iron, lead, and zinc. An electrochemical technique, adsorptive stripping voltamme try, showed the varying abilities of melatonin and its precursors to b ind the metals in situ. The results show that the following metal comp lexes were formed: aluminium with melatonin, tryptophan, and serotonin ; cadmium with melatonin and tryptophan; copper with melatonin and ser otonin; iron(III) with melatonin and serotonin; lead with melatonin, t ryptophan, and serotonin; and zinc with melatonin and tryptophan. Iron (II) showed the formation of an in situ complex with tryptophan only. These studies suggest a further role for melatonin in the reduction of free radical generation and metal detoxification, and they may explai n the accumulation of aluminium in Alzheimer's disease.