Spectroscopy and theoretical studies of natural melanin (eumelanin) and its complexation by iron(III)

Water-Soluble Melanoidin Pigment as a New Antioxidant Component of Fermented Willowherb Leaves (Epilobium angustifolium)

“…A basic possible reason for the high radical scavenging and metal chelating efficiency of EAM is the specific polymeric melanic structure in which the phenolic net can act as a one-dimensional semiconductor and electron acceptor [ 88 ]. The movable balance between the catechol, semiquinone, and quinine forms of melanoidin provides high-speed redox processes and a neutralizing effect on the free radicals and reactive oxygen forms [ 90 ]. Although this has not been discussed previously, the surface functional groups of melanoidins could act as metal chelators and electron conductors.…”

Preparation and related properties of melanin iron supplement

“…Compared with BSM, the partial absorption peak of BM-Fe was weak, indicating that COOH, OH and NH may participate in the chelation of metal ions. 46 After chelation, the absorption at 3365 cm −1 corresponding to N–H and O–H stretching vibration peaks decreased and moved to 3169 cm −1 , which indicated that N–H and O–H are involved in chelation, indicating that the Fe–N bond might replace N-OH. 47 The band corresponding to the carboxyl group (1425 cm −1 ) in BM-Fe has a low intensity compared to that in BSM.…”

Melanin: insights into structure, analysis, and biological activities for future development

“…A distinctive feature that distinguishes eumelanin from pheomelanin is the absence of a sulfur group. 82 Pheomelanin or dopamine melanin chemically modified by amino acids ( e.g. cys-DOPA melanin) is known to have a sulfur content of about 6–16%.…”