Introduction
Vitamin C, the most abundant antioxidant in healthy skin, is well-known for its anti-aging skin effects, like the inhibition of skin damage by free radicals, stimulation of collagen biosynthesis, inhibition of melanogenesis, and improvement of various inflammatory skin disorders. Thus, vitamin C is widely used in skin care products. However, vitamin C is highly unstable in aqueous solution and its stability in cosmetics remains a challenge.
Materials and methods
To address this problem, an anhydrous formulation was developed, consisting of pure L-ascorbic acid (AA) dissolved in two natural polyols compounds. A clinical study was conducted to assess the anti-spot/lightening effect and the acceptability of the new product. Thirty-three healthy women, aged between 33 and 64 years, with lentigo, applied twice daily for 2 months 1 drop of the product on each cheek and on the forehead. The parameters L* (luminance) and b* (cutaneous melanin yellow color) were recorded on day 0 (baseline) (D0), then 28 (D28) and 56 days (D56) after product application. The Individual Typological Angle (ITA°) was calculated from the L* and b* parameters, ITA° being inversely related to pigmentation. The cutaneous acceptability of the product was assessed through an evaluation questionnaire on D56.
Results
The anhydrous formulation stored in glass vials and white bottles remained colorless with a perfect stability of AA for 24 months at room temperature protected from light. L* and ITA° mean values increased on D28 and D56 on the pigmented area, reaching values close to those recorded on the “normal” skin area, where both parameters remained stable. The increase from baseline of both parameters was significantly higher on D28 and D56 on the pigmented skin area than on the “normal” skin. Lighter and less pigmented spots were obtained on D56 in 93% and 90% of subjects, respectively. The product was very well tolerated, assessed as pleasant by 84% of women, with a visible improvement of the skin.
Discussion and conclusion
This new formulation composed of biomimetic active ingredients, like vitamin C, showed a great stability and a significant anti-spot/lightening effect. This study confirmed that the use of pure ingredients, rightly dosed, and naturally assimilated can help the skin restore its balance and adapt to its environment. This is consistent with an ecobiological approach, which considers the skin in relation to its environment, as an ever-evolving ecosystem, for which the natural resources and mechanisms must be preserved and can be applied to develop specifically tailored skincare products.
