Overview on the Kinetics of Carotenoid Antioxidants in Human Skin

The antioxidative role of carotenoids beta-carotene and lycopene in the skin has been investigated and discussed very extensively in many studies and by various scientific groups, during the past years. After the development of the fast and non-invasive optical method based on resonance Raman spectroscopy, it was possible to perform in vivo mea surements on the kinetics of carotenoids in the human skin. In in vivo measurements, it was shown that cutaneous carotenoids decreased after the influence of stress factors, such as illness, fatigue, UV irradiation, and consumption of a high amount of alcohol and subsequent to stress situations. Vice versa, the absence of stress situations on the organism along with a supplementation rich in antioxidant substances give rise to an increase in the concentration of the carotenoids beta-carotene and lycopene in the skin. Thus, the level of carotenoids in the skin can serve as a marker for a whole antioxidative network of human skin. Obtained correlations between the level of lycopene and the roughness of the skin, measured non-invasively on the forehead have proved this hypothesis. The distribution of carotenoids in the skin is inhomogeneous and has a strong gradient with a maximal concentration close to the skin surface (depth 4-8 μm). The topically applied cosmetic formulation containing carotenoids penetrates deep into the stratum corneum down to approximately 24 μm, thus providing protection of the skin surface against the action of free radicals.