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Raman Detection of Car otenoids in Human T issue 195

damage by blocking phototoxic short-wavelength visible light. Also,
MP is thought to directly protect the cells in this area through the
antioxidant function of the carotenoids, lutein and zeaxanthin, which
are well-known scavengers of reactive oxygen species. There is
increasing evidence that MP may help mediate protection of the
cone photoreceptor cells in the macula against visual loss from age-
4–8
related macular degeneration (AMD) the leading cause of irrevers-
ible blindness affecting a large portion of the elderly population.
Since the MP compounds are taken up through the diet, there is a
chance that early age screening of MP concentrations can be used to
identify individuals with low levels of MP. If indicated, dietary inter-
ventions such as increased consumption of lutein and zeaxanthin
containing vegetables or nutritional supplements could be used to
help prevent or delay the onset of the disease.
MP concentrations in the healthy human retina have been assumed
to be highest in the very center of the macula, the foveola, and to drop
9
off rapidly with increasing eccentricity. Recently emerging high-
resolution optical imaging techniques based on lipofuscin fluorescence
(“autofluorescence”) excitation and reflection methods, however, are
beginning to reveal a much more complex behavior of MP distribu-
tions in the living human retina, such as patterns with locally depleted
MP levels and MP distributions with ring-shaped patterns. 10–13 It is
important to confirm these interesting features with an imaging Raman
method, which in comparison to the other methods would be a much
more direct, carotenoid-specific detection. Furthermore, it could pro-
vide a valuable new method that is useful to track MP distributions,
their local MP levels, and potential changes occurring in them upon
the occurrence of vision problems, macular pathology, and subsequent
dietary modifications or supplementation.
In addition to ophthalmology, RRS spectroscopy is interesting also
for the detection of carotenoids in human skin. In this tissue, which
constitutes the largest organ of the human body, the predominant
carotenoid species are lycopene and β-carotene, followed in order of
tissue concentrations by β-cryptoxanthin, lutein, and zeaxanthin. All
are thought to play an important protective role as antioxidants, like in
the protection of skin from premature aging caused by ultraviolet and
short-wavelength visible radiation. The carotenoids, lutein and lyco-
pene, may also have protective functions for cardiovascular health,
and lycopene may play a role in the prevention of prostate cancer. It is
conceivable that skin levels of these carotenoids are correlated with
corresponding levels in internal tissues.
Objective measurements of skin carotenoid levels would be of
interest also for improving dietary data collected in epidemiological
studies, which in turn are used in developing public health guidelines
that promote healthier diets. The protective effects of diets rich in fruits
and vegetables has been observed for many disease outcomes, including
16
various cancers 14,15 and cardiovascular disease. Since carotenoids are a