Chemistry Reference
In-Depth Information
damage both in the mouse and human (Mathews-Roth and Krinsky 1970, 1985, Mathews-Roth 1986;
Stahl and Sies 2004). The specii c, local accumulation of lutein in Monarch and other butterl y larvae
demonstrates that a mechanism exists for the active uptake and the transport of the lutein into the yel-
low regions within these organisms. In total, an average of
4 mg of lutein is present in the epidermis
of a typical Monarch larva. Even higher levels were found in other species, Figure 25.8. The exis-
tence and the identity of a lutein-specii c binding protein responsible for the epidermal accumulation
remains a signii cant and unanswered question.
The concentration of lutein in the yellow regions in all of these larvae is exceptionally high. By way
of comparison, the total amount of carotenoids present in the human epidermis rarely reaches visibly
detectable levels, although consumption of high doses of b-carotene or canthaxanthin are known to
result in visible skin coloration (Mathews-Roth and Krinsky 1984, 1985, 1987, Prince and Frisoli 1993,
Gonzalez et al. 2003, Stahl and Sies 2004). We estimate that the lutein concentration in the yellow
bands of Monarch larvae is in the mM range, and thus even in the black and white regions where the
concentration is lower (
∼
15x) it is still quite signii cant. Carotenoids are known to act as the quench-
ers of singlet oxygen and free radicals at mM levels (Di Mascio et al. 1992). Hence, it is clear that the
lutein concentration throughout the epidermis of Monarch larva is more than sufi cient to provide an
effective protection from photoinduced oxidative damage. A similar conclusion is appropriate for the
other species.
The variation of the lutein concentration across the wide yellow bands of Monarch may be related
to growth within this tissue. Growth occurs at a remarkable rate for these organisms, and it is prob-
able that the carotenoid concentrations within the rapidly growing regions may lag behind slowly
growing regions. Alternatively, the tissue thickness and microstructure, which were not measured,
may vary and contribute to the observation.
The chromatograms from the yellow bands of Monarch show the presence of the apo-carotenoid,
3-hydroxy-10
∼
-apo-b-carotenal, in signii cant, although variable quantities. In some instances, the
amount of this component was >20% of the total carotenoid, as judged from the relative peak height.
The observation of a single oxidation product corresponding to cleavage at a specii c carbon-carbon
double bond site is surprising. Multiple products would be expected to result from nonspecii c oxi-
dative cleavage of the double bonds present in the polyene chain (see Chapter 11 and Caris-Veyrat
et al. 2003). The presence of a single product is suggestive of an enzyme capable of specii cally
cleaving lutein. It is known that b-carotene mono-oxygenase can cleave lycopene eccentrically at
the C10-C9 double bond (Kiefer et al. 2001). A mono-oxygenase capable of cleaving lutein asym-
metrically has not been previously reported but would be consistent with our observations. It is
well known that the visual system of insects utilizes a 3-hydroxy-retinal whereas the mammalian
vitamin A lacks the 3-hydroxyl group. While there may exist a functional role for 3-hydroxy-10
′
-
apo-b-carotenal it is also possible that it is a marker for other metabolic activities. Further work to
quantify the amounts, locations, and conditions that correspond to the observation of higher levels
of 3-hydroxy-10
′
-apo-b-carotenal might provide an insight on this question.
The yellow coloration in the Monarch as well as the larva of three other species of butterl y from
South Florida is exclusively due to the specii c accumulation of exceptionally high levels of lutein
producing a pigmented epidermis. This active accumulation, reminiscent of the specii c accumula-
tion that occurs in the primate macula, indicates that butterl y larva is an excellent animal model for
the study of carotenoid transport and binding. As such, elucidation of the mechanism of transport
and binding of lutein in the epidermis and other tissues of these butterl y larvae may provide insight
into xanthophyll uptake within the human eye (Bhosale et al. 2004).
′
ACKNOWLEDGMENTS
The authors wish to acknowledge the FIU College of Arts and Sciences for their partial support of
this project, and Myron Georgiardis from the Department of Chemistry and Biochemistry Mass
Spectrometry Facility for his assistance.
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