Skin-lightening products revisited

Skin colour typology depends on the amount and location of tis chromophores. Among them, eumelanins derived from 5,6 dihydroxyindole-2-carbonxylic acid (DHICA) and 5,6-dihydroxyindole (DHI), and phaeomelanins are of utmost importance. These biomolecules result from the multi-step enzymatic and non-enzymtic conversion of fyrosine into melanins. Pigmentation disorders are multiple and depend on alterations in the density in active melanocytes, and on specific abnormalities of any of the complex melanogenesis mechanisms. This review presents some ot he main skin-lightening agents with respect to their mechanisms of action and side-effects. Some of the novel compounds may lead to new perspectives in the fields of dermatology and cosmetology. The mehods commonly used to assess efficacy of skin-lightening products rely on in vitro models including cell-free enzymatic assays, melanocyte cultures and reconstructed epidermis bioassays. Animal models have little relevance. Bye contrast, human testing with the support of instrumental evaluations is the most informative.