Tyrosine is first oxidized into dopa, then further oxidized into dopaquinone. There are two types of melanin: reddish pheomelanin and brown-black eumelanin.

Melanins block solar radiation by absorption and scattering UV rays, but it could be demage by over sun exposure.                                                             

    

Human skin is repeatedly exposed to ultraviolet radiation (UVR) that influences the function and survival of many cell types and is regarded as the main causative factor in the induction of skin cancer. It has been traditionally believed that skin pigmentation is the most important photo protective factor, since melanin, besides functioning as a broadband UV absorbent, has antioxidant and radical scavenging properties. Besides, many epidemiological studies have shown a lower incidence for skin cancer in individuals with darker skin compared to those with fair skin. Skin pigmentation is of great cultural and cosmetic importance, yet the role of melanin in photo protection is still controversial. This article outlines the properties of melanin, the regulation of pigmentation. and its effect on skin cancer prevention.

Hyper-Pigmentaion

Pigmentation development in the skin is influenced by of a number of internal and external factors, one of the most influential being UV radiation. This results in the over production of melanin in the skin as a defense mechanism.

Melanins are pigments that determine skin and hair color. These pigments are produced by specific cells called melanocytes in the basal layer of the epidermis. Encapsulated in melanosomes, the melanins are distributed to keratinocytes surrounding the melanocytes.

• There are two types of melanin: reddish pheomelanin and brown-black eumelanin.

• Melanins block solar radiation by absorption and scattering UV rays.

 Biosynthesis of melanins

• Both pheomelanin and eumelanin are formed from tyrosine. The initial step of melanin biosynthesis is catalyzed by an enzyme, tyrosinase, with participation of Cu2+ cations.

• Tyrosine is first oxidized into dopa, then further oxidized into dopaquinone.

• Tyrosinase plays an essential role in the enzymatic control of melanogenesis

Pigmentation During exaggerated sun exposure or in aging, skin pigmentation is disturbed and skin spots may appear on face and the backs of the hands or other uncovered areas.

The more or less dark coloring of the skin and excessive pigmentation or spots are sometimes considered to be aesthetic deficiencies. Therefore, there is a high interest in depigmenting agents.

 

They act by:

Interfering with the synthesis of melanins.

Anti-tyrosinase action, decreasing the functional activity of melanocytes.