Identification of Small Peptides and Glycinamide That Inhibit Melanin Synthesis Using a Positional Scanning Synthetic Peptide Combinatorial Library

Background: Antimelanogenic peptides are potentially useful to treat hyperpigmentation, but many peptides have limited application because of high cost and/or low activity.

Objectives: To identify small and potent peptide inhibitors of cellular melanin synthesis that are useful for cosmetic and medical applications.

Methods: A positional scanning synthetic tetrapeptide combinatorial library was used for screening of potentially active peptides. Antimelanogenic activities of the peptide pools and individual peptides were evaluated in B16-F10 melanoma cells and human epidermal melanocytes treated with alpha-melanocyte-stimulating hormone (α-MSH).

Results: Predicted active tetrapeptide sequences were R-(F/L)-(C/W)-(G/R)-NH . Of the individual tetrapeptides tested, D3 (RFWG-NH ) and D5 (RLWG-NH ) exhibited high antimelanogenic activities. Tetrapeptide D9 (FRWG-NH ) with a sequence identical to that of a portion of α-MSH also showed antimelanogenic activity. Of the tripeptides tested, E5 (FWG-NH ), E6 (LWG-NH ) and E7 (RWG-NH ) were relatively more active. Dipeptide F1 (WG-NH ) and monopeptide G1 (G-NH , glycinamide) retained activity, but G2 (Ac-G-NH ) and G3 (glycine) did not. The antimelanogenic activities of peptides D3, E5, F1 and G1 were verified in α-MSH-stimulated human epidermal melanocytes. Commercially available G-NH ·HCl suppressed the phosphorylation levels of cAMP-responsive element binding protein, protein levels of microphthalmia-associated transcription factor and tyrosinase, l-tyrosine hydroxylase activity of tyrosinase, and the melanin levels in stimulated cells.

Conclusions: Small peptides, including glycinamide and tryptophanyl glycinamide, are potent antimelanogenic agents with potential value for the treatment of skin hyperpigmentation.