Objective Grading of the Appearance of Melanin-Like Materials Using Spectroscopic Analyses

Melanin is a component of many cosmetic or hair care formulations because of its photoprotective and antioxidant ca-pabilities. For such formulations, matching hair or skin tone is important. This report proposes the establishment of a framework to objectively compare different melanin-like materials based upon the intensity of their color and/or their presentation as eumelanin- or pheomelanin-like. Using absorbance spectroscopy from the UV to the near-infrared re-gions of the electromagnetic spectrum, numerical and graphical presentations are proposed to grade the appearance of melanin-like materials. In addition, we highlight FT-IR spectroscopy as a tool to evaluate the presence of carboxylic acid or carboxylate functional groups in the melanin-like materials. Such functional groups may be present due to the specif-ics of the reaction conditions or the choice of purification process and can have an impact on the binding capabilities of the melanin-like materials. The combination of objective parameters related to the type and intensity of the color of a melanin-like material can provide a basis for the proper formulation of melanin-based cosmetics matching any desired skin or hair tone.