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8721685 
Journal Article 
Spectral in vivo signature of carotenoids in visible light diffuse reflectance from skin in comparison to ex vivo absorption spectra 
Andree, S; Reble, C; Helfmann, J 
2013 
2 
4 
323-335 
English 
Objective: To increase the carotenoid concentration in skin by drinking carrot juice to generate an optical response and to determine an in vivo absorption spectrum of the carotenoids and compare it to ex vivo absorption spectra. Material and methods: The first author of the presented study consumed carrot juice over a period of several weeks and during this time regularly performed optical reflection measurements on his palm. The spectroscopic measurements were carried out with a fiber-based sensor using a thermal light source. Absorption coefficients have been deduced from the diffuse reflectance data. Measurements were also performed on a β-carotene solution, on carrot juice and its extracted carotenoids. The correlation coefficient between carrot juice intake in liters and the optical skin signal was used to select an optimal wavelength for carotenoid detection (493 nm). Results: An in vivo signal of the carotenoids was found in the spectral range from 400 nm to 580 nm. A 1-l intake of carrot juice resulted in a 0.6% decrease of the diffuse reflectance. The absorption of hemoglobin interferes with the carotenoid signal even though the blood was pressed away. Consequently, a method was used that could lead to the elimination of this disturbance and an in vivo absorption spectrum from the carotenoids in skin was determined by way of trial. The in vivo carotenoid spectrum and that of the carrot juice were both found to a similar extent to be spectrally broader than the absorption spectrum of β-carotene dissolved in cyclohexane. Conclusion: Detection of carotenoids in skin is possible by diffuse reflectance measurements with a simple spectroscopic optical setup, as it is described in this article. As found by comparing different publications, several geometries for illumination and detection support carotenoid quantification. However, the fiber probe described here is not limited to carotenoid detection and it does not need arrangement of several optical elements such as lenses, mirrors or apertures and therefore requiring less effort for development. To eliminate the interference of hemoglobin, the authors suggest the combination of pressure and the described software method. Other publications have reported hemoglobin interference with respect to in vivo carotenoid measurement. As the carotenoids are mainly found in the bloodless epidermis, setups are suggested which use smaller sampling volumes. 2013 Walter de Gruyter GmbH, Berlin/Boston. 
Carrot juice; Hemoglobin; Optical reflection measurements