Lightening and Illuminating Skin With Acetylated Hydroxystilbenes From Rheum rhaponticum

Increased melanin pigmentation is a physiological mechanism that the skin adopts to protect itself from the damaging effect of sustained and prolonged UV light exposure. Melanin pigment, produced by melanocyte cells in the basal layers of the epidermis, is transferred to the keratinocytes in the epidermis and sits on the top of the keratinocyte’s nucleus to protect the cell’s DNA. However, in some conditions (i.e., inflammation or a hormonal imbalance) and with increasing age, the deposition of melanin in the epidermis increases. This is particularly evident in extreme cases such as melasma, where patchy melanin formation on skin is observed.1 Skin inflammation and sustained damage can also be a fundamental trigger for excessive pigmentation,2, 3 with clinical relevance in the case of post inflammatory pigmentation.4 Other examples of increased pigmentation due to skin irritation and/or inflammation are documented in women developing axillary melanin spots due to hair removal irritation5 or in individuals suffering from acne.6

Those experiencing skin pigmentation as a result of inflammation or irritation are often associated with phototypes III–IV on the Fitzpatrick Scale. In order to even skin tone, decrease skin pigmentation and reduce the formation of dark spots, a series of lightening and depigmenting agents have been developed over the years targeting different steps of the melanogenesis process.7, 8 Among the agents most utilized for this purpose are: hydroquinone, kojic acid, arbutin, vitamin C, etc. However, many of these agents have been questioned for their safety7, 9 and have been restricted for their use in many countries. Therefore novel skin lighteners and depigmenting agents with a proven efficacy and safety profile remain a prominent need in personal care.

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