Hyperpigmentation: a challenge for high melanin content phototypes

Chronological or photoinduced ageing, hormonal disorders (contraceptives, pregnancy and menopause, etc.), repeated exposure to the sun, and reactions to irritation or inflammation (skin healing, acne or the side-effects of medical treatments), lead to the appearance of skin pigmentary problems.

Melanogenesis disorders are common in people of colour (phototypes IV to VI). These disorders are among the top five most common dermatologic diagnoses in individuals of African descent. A recent study conducted in Durban, KwaZulu- Natal, noted that dyschromias are the third most common dermatologic diagnosis in the area. The most common subtypes of pigmentary disorders include (in order of frequency) vitiligo, post-inflammatory hyperpigmentation and melasma 1 .

Stress-induced hyperpigmentation, due either to UV and/or inflammation, is an important challenge of high melanin content phototypes. The demand for eventone skin makes it an unavoidable topic for the cosmetics industry. Hydroquinone was used originally and showed very good whitening performance. However, the toxicological profile of the molecule has resulted in it being forbidden in many countries. Other molecules such as arbutin, kojic acid and vitamin derivatives are now used as safer alternatives in even tone and brightening products. Wesource by Seppic, represented locally by CJP Chemicals, offers two products with original mechanisms of action which not only focus on basal pigmentation but also on stress-induced melanogenesis, meeting the needs of skin of colour.

SepiwhiteTM MSH

Melanocortin, or alpha-Melanocyte- Stimulating Hormone (α-MSH) is a major factor in the regulation of skin pigmentation. It acts to stimulate melanogenesis via a type 1 membrane receptor, MC1R. Studies conducted on human skin have shown that subcutaneous injection of α-MSH induced hyperpigmentation. The α-MSH is increased both in hyperpigmented areas and in areas exposed to UV radiation. A study also revealed that melanogenesis in melasma involves epithelial secretion of α-MSH².

The MC1R receptors, activated by α-MSH and its analogues, are inhibited by AGRPs (Agouti-related protein), natural antagonists present in skin. These proteins have a phenylalanine amino acid in a key position which plays an essential role in binding to MC1R receptors, leading to an inhibition of melanogenesis.

In light of these findings, Sepiwhite TM MSH was developed as a highly purified lipo-amino-acid (Aminovector™), based on phenylalanine. The mechanism of action of Sepiwhite™ MSH relies on its biomimetic composition and structure. The purified undecylenoyl phenylalanine molecule has a high affinity with the MC1R receptor and competes with its natural ligands. The antagonist properties of Sepiwhite™

MSH on the MC1R receptor lead to theupstream inhibition of melanogenesis.Complementary tests also demonstrateda downstream inhibition of melanogenesis(see Figure 1), making Sepiwhite™ MSH amulti-target lightening agent.

In vitro tests were conducted onmelanocytes to assess the performanceof Sepiwhite™ MSH on basal and stressinducedconditions. In basal conditions,Sepiwhite™ demonstrated a 66% reductionin intracellular melanin production, higherthan arbutin, kojic acid and magnesiumascorbyl phosphate. Even thoughSepiwhite™ MSH demonstrated a similarmelanin reduction level in UVB-inducedconditions (66%), it showed the bestreduction in α-MSH-induced conditions(145%), higher than all other benchmarks,including hydroquinone. The results showSepiwhite™ MSH demonstrates extremelygood tolerance and no phototoxicity.