November 1998 Volume 1, Issue 5
|
|  Yüklə 64 Kb.
|
. . . Newsletter New Potentials for Skin Lightening FARMECO Co. We live in a world where everyone wishes to enhance their appearance. For most of the world, enhancing appearance involves reducing or evening the pigmentation of the skin. The largest perceived difference in skin tone is between constitutive and adaptive pigmentation. Constitutive pigmentation is the natural level of pigmentation in skin that has not been damaged or exposed to light. Adaptive pigmentation is the additional pigmentation due to UV exposure, acne, skin damage or pregnancy. A A Comparison of Skin Lightening Agents FARMECO For all skin types, the skin lightening agents can be used to treat pigmentation disorders such as freckles, pregnancy masks, age and sun spots. A comparison of skin lightening agents has been issued on Journal of Cosmetic Science, Vol. 49, No. 3, May-June 1998, p. 208-290. Skin lightening agents compared here are all inhibiting the enzymatic activity of tyrosinase.
Melanin synthesis is a complex process controlled partly by an enzyme called tyrosinase and it is only a part of the melanogenesis process. Melanogenesis also involves the development of the melanosomes, the organelle of the melanocyte in which melanin is synthesized and the subsequent transfer of the melanosomes to keratinocytes. Environment, genetics and hormone flux influence the process of melanogenesis. There are several routes by which melanogenesis can be slowed down. Perhaps the best way is to reduce the amount of UV light that reaches the skin. If people cannot stay out of the sun, they should attempt to regularly use sunscreens. UV radiation stimulates the generation of tyrosinase and thus pigmentation. There are several ways to reduce the development of adaptive pigmentation. The most talked about means of reducing pigmentation is the reduction of the tyrosinase activity. This can be accomplished by blocking the production of tyrosinase, inhibiting the enzymatic activity of tyrosinase, or preventing the uptake of tyrosinase by the melanosomes. SKIN COLOR AND MELANINSkin color is mainly determined by the amount of melanin in the skin. Melanin biosynthesis can be blocked at various points. Skin lightening agents can inhibit or even reverse melanin biosynthesis and are thus useful in whitening or lightening the human skin. STABILITYKojic acid usually turns yellowish brown with time in the finished product. Hydroquinone solution becomes brown on exposure to air as a result of oxidation and must be stabilized (oxidation of Kojic acid and hydroquinone results in reduced skin whitening effectiveness). Arbutin has by far higher stability than hydroquinone. Magnesium Ascorbyl Phosphate (MAP) is stable in formulation and especially in the encapsulated form. SAFETY AND EFFICACYHydroquinone can be irritating and cause redness and burning. More importantly, it has been shown to cause exogenous ochronosis (a serious cytotoxic side effect) which has resulted in a ban on its use in South Africa, Thailand, Far East and other countries. In the European Union usage is allowed at only 2%. Arbutin has far higher safety than hydroquinone, has no irritation and virtually no sensitization. In addition, hydroquinone has cytotoxic effect on melanocytes, which causes high toxicity to the skin. 
-/+ indicates minimum value +++++ indicates highest value  . . . . . . . . . . . . . . . . . . . . . . .
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
