[UV-Vis spectroscopic study of aluminum-manganese cooperative effect on the melanin formation from DOPA oxidation].

The effect of aluminum and manganese ions on the melanin formation from oxidized DOPA was investigated by UV-Vis spectroscopy. In the weak acidic buffer solution (pH 5.5), aluminum and manganese ions have cooperative effect on the melanin formation. Aluminum is not a transition metal and therefore cannot initiate oxidative effect. However, manganese ions initiate the oxidation of DOPA to yield dopachrome. Aluminum ions can greatly catalyze the conversion reaction of dopachrome to form 5,6-dihydroxyindole, which is a key step in the biosynthesis of melanin. Its product is further oxidized and polymerized immediately to produce melanin. Therefore, the cooperative effect of manganese and aluminum ions increases the melanin formation from DOPA and enhances the oxidative stress.