Eumelanin
The brown-black form of melanin that provides effective photoprotection by absorbing UV radiation. Eumelanin is more protective than pheomelanin (red-yellow melanin). Afamelanotide specifically stimulates eumelanin production through MC1R activation on melanocytes.
Technical Context
Eumelanin is a heterogeneous polymer of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) units. Its dark colour (brown to black) results from extended conjugation within the polymer. Photoprotective properties: eumelanin absorbs UV radiation across a broad spectrum (UVB 290-320nm, UVA 320-400nm, and visible light), dissipating >99.9% of absorbed energy as heat through ultrafast internal conversion (photophysics preventing photochemical damage). Eumelanin also scavenges reactive oxygen species generated by UV exposure. The photoprotective capacity of eumelanin is the biological basis for afamelanotide's therapeutic effect in EPP — increased eumelanin deposition in the epidermis reduces the amount of UV-visible light that penetrates to deeper skin layers where protoporphyrin IX is deposited, thereby reducing phototoxic reactions.