We present our initial observations regarding the effect of the presence of L-tyrosinate (= L-tyrosine disodium salt) on the auto- or Fe2+/H2O2-mediated oxidation of various catecholic substances into melanin-like pigments. We observed that L-tyrosinate inhibited the Fe2+/H2O2-mediated oxidation. In contrast, L-tyrosinate promoted the auto-oxidation of ortho-diphenols like L-DOPA, dopamine, epinephrine, norepinephrine, catechol or pyrogallol, but not a meta-diphenol like resorcinol. In addition, we briefly demonstrated the melanogenic properties of cell culture media containing L-tyrosinate. The reactions were monitored using UV-Vis spectroscopy and size exclusion chromatography. For a reaction between L-tyrosinate and L-DOPA, a large scale experiment was set up allowing us to isolate, purify and characterize using FT-IR spectroscopy the melanin-like material obtained. We discuss our observations in the context of the in vitro and in vivo study of melanogenesis and provide some directions for future research efforts.
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