A new generation of skin brightening ingredients

This trend for a white complexion has continued to the present day. Due to the fact that the majority of women are concerned about skin darkening, whitening products are a key segment of the skin care market in China. It makes up nearly 30% of the total skin care market in China, and Chinese consumers are big users of facial whitening products with facial care accounting for over 80%. Consumers outside of Asia are also concerned about skin darkening and complexion issues. For instance people of dark skin types are particularly affected by facial hyperpigmentation and more and more consumers feel uncomfortable with their axillary zone also being subject to darkening. Caucasian women however are more concerned about dark spots and freckles on face and hands. Nowadays, the whitening market has come a long way from the basic ‘whitening’ approach, aimed at ethnic consumers with darker skin mainly in Asia or the Middle East to new growing targets driven by the ageing of the population and men’s increasing interest in grooming. Consumers are globally concerned about sun ageing and are looking for products to protect their skin to avoid premature age spots or wrinkles, skin irritations or hyperpigmentation. BB and CC creams that cover blemishes, even skin tone and brighten complexion, are already used daily by 28% of South Korean consumers, and also by 24% of Brazilians (Symrise LE Consumer database 2013, 14,000 interviews in BR, IN, MX, KR, RU, UK, US). From a consumer perspective brightening one’s skin is also a matter of skin fairness and tone evenness. A recent ‘light brown’ to ‘dark skin’ exploration in India, Brazil, Kenya and South Africa highlights for example the social dimension of skin tone. In India consumers will compare themselves to others a lot, and feel miserable if the skin is not considered fair. “Everyone wants to look good, everyone wants to look fair,” says 32-year-old Rajiv from New Delhi.

Need for innovation

To meet the increasing global need for modern, safe and effective skin lightening ingredients the challenge is on the raw material suppliers’ side. Many common skin lightening ingredients in the cosmetic market are reported to be unsafe, cytotoxic, unstable or ineffective at low concentrations. The most common lightening ingredients today are the tyrosinase inhibitors kojic acid and arbutin as well as ascorbic acid derivatives. However, all these compounds exhibit significant disadvantages: kojic acid has been shown to be sensitising and to exhibit adverse thyroid effects at high concentrations. Arbutin is suspected to be a hydroquinone precursor. Hydroquinone is known for its toxic action on skin cells and therefore its cosmetic use has been restricted or banned in many countries. Ascorbic acid derivatives are only effective in high concentrations and difficult to stabilise in cosmetic formulations. Inspired by a natural pine extract in order to meet the demand for safe and efficient skin lightening active ingredients, a series of hydroxystilbene derivatives was synthesised and screened for antioxidant efficacy as well as for tyrosinase inhibitory activity. Based on various parameters including efficacy and stability, 4-(1- phenylethyl)-1,3-benzenediol (phenylethyl resorcinol), was found to be the best candidate for further studies. In a cellular assay on B16V melanoma cells, phenylethyl resorcinol was the most potent inhibitor of melanin synthesis among all the compounds investigated with an IC50 of 2 M. A MTT assay on B16V cells showed that the lightening effect of phenylethyl resorcinol was not due to cytotoxicity. On pigmented 3D epidermal models, 0.1% of phenylethyl resorcinol led to an almost complete suppression of melanin synthesis after 14 days of incubation. Additionally, it exhibits very potent antioxidant activity determined by TEAC assay. To evaluate the lightening efficacy of phenylethyl resorcinol in a more relevant situation an ex vivo study using human full-thickness skin explants was performed. In two different phototypes, light and dark (pigmentation scale: very light, light, intermediate, tanned, brown, and dark), phenylethyl resorcinol applied in emulsion showed a significant reduction of melanin content after 6 days (Fig. 1). As expected the lightening effect was more pronounced on the light phototype.