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Carotenoids are important substances for human skin due to their powerful antioxidant properties in reaction of neutralization of free radicals and especially reactive oxygen species, including singlet oxygen. Concentration of carotenoids in the skin could mirror the current redox status of the skin and should be investigated in vivo. Optical methods are ideally suited for determination of carotenoids in mammalian skin in vivo as they are both noninvasive and quick. Four different optical methods could be used for in vivo measurement of carotenoids in the human or animal skin: (1) resonance Raman spectroscopy; (2) Raman microscopy; (3) reflection spectroscopy; (4) skin color measurements. The advantages, shortcomings, and limitations of the above-mentioned optical methods are discussed. [ABSTRACT FROM AUTHOR]

Background: The cutaneous antioxidants form an efficient protection system against the destructive potential of free radicals, produced by environmental factors, such as UV-sun irradiation, hazardous substances and lifestyle habits. Most of the antioxidants cannot be produced by the human organism. Thus, they have to be incorporated by food and beverages. Material and Methods: In the present manuscript, the distribution of carotenoids as a marker for antioxidative potential in human skin was investigated with two different in vivo Raman spectroscopy methods with an excitation wavelength of 785 nm (Skin Analyzer) and at 488 nm (resonance Raman spectroscopy). The carotenoid profile was assessed at three different anatomical locations (palm, forehead and volar forearm) in 12 healthy volunteers. Results: In untreated skin, the major fraction of the carotenoids is located in the upper part of the stratum corneum (SC). The amount of carotenoid is lower in the upper part of the SC on the forearm compared to forehead and palm shown with both methods. Both methods detect similar distinction patterns of carotenoid levels for the three anatomical locations. Conclusion: The present study supports the hypothesis that antioxidative substances; here carotenoids, are secreted via eccrine sweat glands and/or sebaceous glands to the skin surface. Raman spectroscopic methods are an efficient tool to analyze the distribution of carotenoids in the human skin over time and with the Skin Analyzer over different layers of the epidermis. Resonance Raman spectroscopy is suited to analyze deeper parts of the skin. [ABSTRACT FROM AUTHOR]

Abstract: Carotenoids, naturally occurring lipophilic micronutrients, possess an antioxidant activity associated with protection from damage induced by free radicals. The present study investigated an innovative non-invasive method to measure cutaneous levels of lycopene and β-carotene and to monitor the distribution of orally administered lactolycopene in human skin and plasma. A double-blind placebo-controlled randomized study was performed in 25 volunteers, who were under a lycopene-deprived diet (4weeks prior to study until end of the study) and orally received either lactolycopene or placebo for 12weeks. Skin and plasma levels of lycopene and β-carotene were monitored monthly using Raman spectroscopy and HPLC, respectively. Cutaneous levels of lycopene and β-carotene monitored by resonance Raman spectroscopy showed high reliability. Irrespective of the investigated area, cutaneous levels were sensitive to lycopene deprivation and to oral supplementation; the forehead showed the closest correlation to lycopene variation in plasma. Plasma and skin levels of lycopene were both sensitive to oral intake of lactolycopene and, interestingly, also skin levels of β-carotene. Thus, oral supplementation with lycopene led to an enrichment of β-carotene in human skin, possibly due to the fact that carotenoids act in the skin as protection chains, with a natural protection against free radicals. [Copyright &y& Elsevier]