A zinc-glycine complex is a possible skin-lightening active due to its inhibition of melanocyte growth factors, according to scientists.
The market for skin lightening products is strong, particularly in Asian regions however the scientists also note that the complex may be beneficial against the pigmentation spots often associated with skin ageing.
The research, published in this month's International Journal of Cosmetic Science, suggests that a zinc(II) complex with glycine (Zn(II)(gly)2
) may prevent the melanin production that normally occurs when a cell is hit with UV radiation.
Melanin production reduced to 75 per cent
The scientists, led by Y Ochiai from the Cosmos Technical Centre in Tokyo, Japan, reported that the zinc-glycine complex reduced melanin production in both cell cultures and reconstructed human epidermal equivalents.
UVB-irradiation of keratinocytes that had not been treated with the zinc-glycine complex led to an increase in melanocyte production of 110 per cent, reported the team.
However, treating the keratinocytes with the zinc-glycine complex significantly suppressed melanocyte proliferation.
Results from investigations using reconstructed human epidermal equivalents further backed up these findings and treatment of the zinc-glycine complex was found to decrease melanin production to 75 per cent compared to the non-treated control.
Zinc-Glycine stimulates metallothionein
The zinc-glycine complex works by stimulating the production of an endogenous antioxidant called metallothionein - a peptide that occurs naturally within the body.
In turn, metallothionein is thought to inhibit the secretion of various melanocyte growth and activating factors that are produced by keratinocytes when they are hit with UVB rays.
Such melanocyte-activating factors include endothelin-1 and prostaglandin E2
and lead to melanin production.
Therefore, in zinc-glycine treated cells metallothionein is produced in larger quantities which inhibits the production of melanocyte-activating factors leading to lower melanin production and consequently lower pigmentation.
The effect is thought to rely on the antioxidant properties of metallothionein, leading the scientists to conclude that "Zn(II)(Gly)2 would be a candidate for a new skin whitening active…by the upregulation of intracellular endogenous antioxidant ability."
Source: International Journal of Cosmetic Science
Issue 30, pages 105-112
"A Zn(II)-glycine complex suppresses UVB-induced melanin production by stimulating metallothionein expression"
Y. Ochiai, S. Kaburagi, Y. Okano, H. Masaki, M. Ichihashi, Y. Funasaka and H. Sakurai.