In clinical studies, the concentration of carotinoids in the skin or blood plasma was measured noninvasively by reflection spectroscopy. In this study, the reflection spectroscopy from the short-wave UV range to the long-wave infrared range was used. Two different light intensities were focussed at two skin depths: up to a depth of 0.5 mm with the epidermis, the vascular capillary network and the papillary loops and up to a depth of 1.5 mm with the medium sized vessels. Figure 1 shows the shallow as opposed to the deep measurement of reflection spectroscopy schematically. These two methods of measurement were developed for separately measuring the carotinoid concentration in the outer skin and in the deep layers. The kinetics of carotinoids in the skin after short-term application thus becomes clearer. In the measurement up to a depth of 0.5 mm the maximum is already reached after four minutes and maintained for over 80 minutes. The accumulation is concentrated in the subpapillary vascular network and the ascending capillary loops. The measurement of up to a depth of 1.5 mm reveals a relatively low concentration in the tissue immediately after the start of application, but a very much higher concentration 20 minutes after the end.

Focussing on two vascular networks at different levels is significant for dermatological sun protection because the particularly exposed capillary loops and the papillary dermal connective tissue surrounding them need protection. These capillary loops are nearer the skin surface than the corresponding epidermal regions (Figure 1) and represent an essential part of the carotinoid-containing connective tissue which is specifically covered solely by the shallow measuring variant. Other parts of the vascular system and the connective tissue are not as affected by light because they are better protected by the epidermis.

Under the experiment conditions of the non-physiologically high in-use concentration (0.01 percent solution = 190µmol/l) over a period of 10 minutes as a short term application (190 µmol) and over 130 minutes as a long-term application (2.740 µmol), followed by washing, the carotinoid is differently distributed in the surface and deep vascular networks as a function of time. The subpapillary network fills up quickly. The endothelia appear to store large amounts of carotinoids very quickly and initially delay a distinct increase in concentration in the deeper venous vessels.

The grey region in Figure 2 reproduces the accumulation measured in the human study after 12 weeks’ supplementation in physiological concentrations (deep variant) and lies over the values of the shallow 0.5 mm measurement. In addition, the carotinoid accumulation probably occurs partly outside the vessels on account of the chronic supplementation.

Source: Pittermann, W.; Jungmann, H.; Kietzmann, M.; Schmitt, M.; Blume, B.; Spektroskopie im UV- und sichtbaren Bereich am isoliert perfundierten Eutermodell nach systemischer Carotinoidapplikation, Kosmetische Medizin 19 (1998) 152-162

Literature

(1) Schweitzer, C.; Natural Mixed Carotenoids Provide ‘Inside-Outside’ Sun Protection, Drug & Cosmetic Industry 161 (1997) No. 6, 40-44; Pittermann, W.; The Isolated Perfused Bovine Udder Skin: A Natural in vitro Skin Model, Skin Care Forum No. 15 (1996) 1-5




Dr. Wolfgang Pittermann, DVM (ECVP), was formerly head of the Laboratory for Experimental Toxicology and Pathology. Now he is in charge of Henkel's research platform “Biochemistry of the Skin” in the fields of experimental dermatology for the penetration/irritation in the skin and mucous membrane as well as new technologies.