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PS Bernstein, D-Y Zhao, F de Moura, C Aebischer, F Khachik; Metabolic Transformations of Carotenoids in Ocular Tissues of Humans and Non-Primate Animal Models . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3603.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To determine the absolute configuration and stereochemistry of xanthophyll carotenoids in human, quail, and frog ocular tissues in comparison to serum and liver and to elucidate the most likely pathways for metabolism of dietary (3R,3'R,6'R)-lutein and (3R,3'R)-zeaxanthin in the eye. Methods:Configurational isomers of carotenoids and their metabolites from pooled human, quail, and frog serum, liver, retina, RPE/choroid, ciliary body, iris, and lens were extracted, identified, and quantified by reverse-phase, normal phase, and chiral HPLC. Results:(3R,3'S;meso)-Zeaxanthin, a nondietary carotenoid, was abundant in human macula and retina, but was undetectable in liver and serum. Quails and frogs exhibited comparable ocular specific presence of (3R,3'S;meso)-zeaxanthin in their retinal tissues. Other carotenoid metabolites such as (3R,3'S,6'R)-lutein (3'-epilutein) and 3-hydroxy-ß ,ϵ-carotene-3'-one were also ocular specific, but to a lesser extent. Conclusion:The most likely metabolic transformations of carotenoids in the human eye involve a series of oxidation-reduction and double-bond isomerization reactions. Quails and frogs appear to possess similar biochemical pathways for conversion of dietary (3R,3'R,6'R)-lutein and (3R,3'R)-zeaxanthin to metabolites observed in humans and thus may serve as excellent nonprimate animal models for metabolic studies and for the isolation of the relevant enzymes.
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