Appearing as eumelanin or as pheomelanin and the push towards eumelanin by cysteine.

This report is a combination of new and former experimental results collected over the past three years. It details our observations and spectroscopic studies of the air-mediated oxidation of a wide variety of catecholic precursors into melanin-like materials. Depending on the precursor involved and the reaction conditions employed, dark-brown to black or yellow to rusty-orange colored reaction mixtures, akin to eumelanin- or pheomelanin-like materials, can be obtained. This report expands and confirms an earlier report that behind the dark colors of eumelanin-like materials, distinct, light-colored, pheomelanin-like materials are hidden. In addition, this report expands and confirms earlier observations regarding the effect of the presence of amino acids on the color of the reaction mixture; particularly the effect of the presence of cysteine. The presence of cysteine delays the onset of color formation and leads to dark-colored reaction mixtures; turning pheomelanin-like reaction mixtures into eumelanin-like mixtures. Visible and infrared spectroscopic analyses were made to evaluate the nature, eumelanin- vs. pheomelanin-like, of the materials generated under the varying reaction conditions. Reactions involving epinephrine as the precursor presented unique results which are detailed in this report.