44] Carotenoids in human skin: Noninvasive measurement and identification of dermal carotenoids and carotenol esters

Abstract

Skin is the major light-exposed tissue and thus is susceptible to photooxidative stress. In vitro studies demonstrated that carotenoids interact with light of different wavelengths and are capable of scavenging reactive oxygen species, especially those formed in photooxidative reactions. Carotenoids efficiently scavenge singlet molecular oxygen and excited triplet carbonyls, which are formed on photoexcitation of sensitizer molecules. Protective effects of carotenoids in the skin were shown in the treatment of a genetic disorder, erythropoietic protoporphyria. In this disease, exceptionally high amounts of the photosensitizer protoporphyrin generate reactive intermediates in photooxidative reactions. The excited sensitizers and/or subsequently formed reactive triplet carbon species or singlet molecular oxygen are the reactive agents responsible for damaging reactions with biological macromolecules. The symptoms of erythropoietic protoporphyria are alleviated on treatment with high doses of β-carotene. Dermal accumulation of β-carotene attracted attention, as it has been speculated that carotenoids contribute to protection against acute and chronic exposure to ultraviolet (UV) light. Although the protective effects of carotenoids toward skin lesions are still under investigation, β-carotene supplements are in use as oral sun protectants. Little is known about the accumulation of carotenoids in skin and their distribution in various skin areas. The dermal levels of carotenoids can be measured noninvasively by reflection photometry, which was used to follow β-carotene levels in skin after supplementation.