Cysteamine Crème : Les preuves scientifiques de son efficacité
Skin whitening agents used for the treatment of skin hyperpigmenting disorders (such as melasma (pregnancy mask) and lentigo) but also in skin whitening of normal skin belong to a few family groups of chemicals.
The most important of these groups are the phenols, catechols and thiols:
- Examples of phenolic and catecholic skin whiteners are hydroquinone and 4-isopropyl catechol; those substances act prinicpally as melanocytotoxic molecules (melanocyte killing for example). The cytotoxic effect of phenols and catechols has caused them to be banned as cosmetic ingredients.
- On the contrary thiols (molecules containing an SH- group) usually exert their depigmenting effect through the inhibition of melanin synthesis. Thiols can act:
- as inhibitors of several enzymes involved in melanin synthesis (peroxidase and tyrosinase)
- as quenchers of melanin intermediates such as dopaquinone.
- as metal ion chelators thus enabling removal of iron and copper ions involved in melanin synthesis. This blocks the synthesis of melanin through the inhibition of Fenton-like reactions.
- Examples of thiolic depigmenting agents are methimazole and mercaptoethylamines such as Cysteamine Hydrochloride.
More simply, how does it work ?
- Contrary to other skin depigmenting agents which are only inhibitors of the enzyme tyrosinase, cysteamine is an inhibitor of both tyrosinase and peroxidase in melanocytes (pigment cells).
- Tyrosinase is responsible for mediating the first steps in melanin (skin pigment) synthesis and peroxidase mediates the last steps in this pathway.
- By inhibiting both enzymes, cysteamine inhibits the melanin synthesis pathway in several steps.
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