[Nle4, D-Phe7] alpha-MSH Peptide (melanotan I) is a synthetic analog of the naturally occurring melanocortin peptide hormone alpha-melanocyte stimulating hormone (alpha-MSH) that is an agonist for melanocortin receptors (MC1R, MC3-5R). Alpha-MSH and analogs cause melanin production in skin cells, thereby reduce UV damage by sun exposure.Ac-Ser-Tyr-Ser-Nle-Glu-His-D-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2 or Ac-SYS-Nle-EHfRWGKPV-NH2