Table 1 Characteristics of different types of melanin
From: Melanin in fungi: advances in structure, biosynthesis, regulation, and metabolic engineering
Type of melanin | Precursor of each melanin type | Monomer of each melanin type | Technology for melanin structure elucidation | Properties of melanin type | References |
|---|---|---|---|---|---|
Eumelanin | 5,6-dihydroxyindole (DHI)
|
| Chemical degradation methods, HPLC, ESR spectroscopy | Photoprotective and antioxidant properties, unusual electrical conductivity | |
5,6-dihydroxyindole-2-carboxylic acid (DHICA)
|
| Chemical degradation methods, HPLC, ESR spectroscopy | Decreased visible light absorption and paramagnetic response relative to DHI-based melanins, markedly enhanced antioxidant properties | ||
Pheomelanin | 5-S-cysteinyl-DOPAquinone
|
| Chemical degradation methods, HPLC, | Phototoxic (can lead to ROS production) | |
Pyomelanin | Benzoquinone acetic acid
|
| Fourier-transform infrared (FTIR), solid-state NMR (ssNMR), gel permeation/size exclusion chromatography (GPC/SEC) | Water-soluble, non-cytotoxic, radical scavenging activity, hyper thermostable | |
DHN-melanin | 1,8-DHN
| – | EPR, solid-state NMR (ssNMR), UV–Vis and IR spectra | Redox and radical scavenging activities, antimicrobial activity |
