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)-NH2 . Of the individual tetrapeptides tested, D3 (RFWG-NH2 ) and D5 (RLWG-NH2 ) exhibited high antimelanogenic activities. Tetrapeptide D9 (FRWG-NH2 ) with a sequence identical to that of a portion of α-MSH also showed antimelanogenic activity. Of the tripeptides tested, E5 (FWG-NH2 ), E6 (LWG-NH2 ) and E7 (RWG-NH2 ) were relatively more active. Dipeptide F1 (WG-NH2 ) and monopeptide G1 (G-NH2 , glycinamide) retained activity, but G2 (Ac-G-NH2 ) 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-NH2 ·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.

Human skin-depigmenting effects of resveratryl triglycolate, a hybrid compound of resveratrol and glycolic acid.

OBJECTIVES: Resveratryl triglycolate (RTG) is a hybrid compound derived by the esterification of resveratrol with glycolic acid. This compound has been previously shown to inhibit cellular melanin synthesis in vitro. This study aimed to examine the in vivo skin-depigmenting efficacy of RTG in human participants. METHODS: In total, 22 women aged between 25 and 49 years with Fitzpatrick skin type III or IV were enrolled. Their forearms were exposed to UV to induce artificial pigmentation. The test product containing 0.4% RTG or the control product was applied twice daily for up to 8 weeks after the artificial pigmentation. The participants visited the research centre every 2 weeks and were subjected to skin assessments. RESULTS: Visual assessment of pigmentation degree and instrumental analysis of melanin index, skin lightness (L* value) and skin colour (individual typology angle, ITAo ) indicated enhanced depigmentation of the skin in the test group, compared with the control group, in Weeks 6 and 8 (P < 0.05). No adverse skin reactions were observed in any of the participants during the entire test. CONCLUSION: This study demonstrated the skin-depigmenting effects of RTG in human participants.

Antimelanogenic effects of luteolin 7-sulfate isolated from Phyllospadix iwatensis Makino.

BACKGROUND: Abnormal deposition of melanin may cause an aesthetic skin problem; therefore, the control of unwanted excessive melanin synthesis is the major goal of cosmetic research. OBJECTIVES: To identify novel tyrosinase (TYR) inhibitors from marine plants and examine their cellular antimelanogenic effects. METHODS: The extracts of 50 marine plants endemic to Korea were screened against human TYR. Active constituents were then isolated from the selected plant extracts that showed potential and their chemical structures elucidated. Furthermore, their antimelanogenic effects were examined using murine melanoma B16/F10 cells and human epidermal melanocytes (HEM). RESULTS: Among the tested extracts, that of Phyllospadix iwatensis Makino exhibited the strongest human TYR inhibitory activity. The active constituents were purified from the butanol fraction of the P. iwatensis extract and identified as hispidulin 7-sulfate and luteolin 7-sulfate. Luteolin 7-sulfate inhibited human TYR more strongly than hispidulin 7-sulfate, luteolin, hispidulin and arbutin. Furthermore, luteolin 7-sulfate showed lower cytotoxicity than luteolin in both B16/F10 cells and HEM. Luteolin 7-sulfate attenuated cellular melanin synthesis more effectively in B16/F10 cells and HEM stimulated by α-melanocyte-stimulating hormone and l-tyrosine than arbutin. CONCLUSIONS: This study demonstrates that luteolin 7-sulfate isolated from P. iwatensis is a human TYR inhibitor with advantageous antimelanogenic properties, and would be useful for development as a therapeutic agent for the control of unwanted skin pigmentation.