Lutein and zeaxanthin

Most carotenoids have no pro-vitamin A activity with the notable exceptions of P-carotene, and to a lesser extent a-carotene and P-cryptoxanthin. They act as macular pigments (lutein and zeaxanthin) and they have antioxidant and biochemical properties other than pro-vitamin A activity. 

The relationship between serum and tissue concentrations of lutein and zeaxanthin was recently studied by Johnson et al, (2000). Dietary intake of xanthophyll-rich vegetables (for example, spinach and com) resulted in significant increases in lutein concentration in serum, adipose tissue and buccal cells, and this correlated with changes in MP density. However, P-carotene and lycopene are normally the major carotenoids detected in buccal cells (Peng et al, 1994). 

JOHNSON E J, HAMMOND B R, YEUM K, J, QIN J, WANG X D, CASTANEDA C, SNODDERLY D M and RUSSELL R M (2000) Relation among serum and tissue concentrations of lutein and zeaxanthin and macular pigment density. Am J Clin Nutr. 71(6) 1555-62. 

Landrum, J.T., Bone, R.A., and Herrero, C., Astaxanthin, cryptoxanthin, lutein, and zeaxanthin, in Phytochemicals in Nutrition and Health, CRC Press, Boca Raton, FL, 2002. 

Fruifs and vegetables also contain ofher bioactive substances such as polyphenols (including well-known pigments anthocyanins, flavonols) and non-provitamin A carotenoids (mainly lycopene, lutein, and zeaxanthin) that may have protective effects on chronic diseases. Polyphenols and carotenoids are known to display antioxidant activities, counteracting oxidative alterations in cells. Besides these antioxidant properties, these colored bioactive substances may exert other actions on cell signaling and gene expression. 

Carrots were also the main sonrces of a-carotene, whereas tomatoes and tomato prodncts were the major sources of lycopene. Lutein was mainly provided by peas in the Republic of Ireland and United Kingdom. Spinach was found to serve as the major source in other countries. Lutein and zeaxanthin xanthophylls are found in a wide variety of fruits and vegetables, particularly green leafy vegetables, but also in some animal products such as egg yolks. In all countries, P-cryptoxanthin was obtained primarily from citrus fruits. 

A close relationship exists between physicochemical properties of pigment molecules and their ability to be absorbed and thus to exhibit biological functions. Carotenoids are hydrophobic molecules that require a lipophilic environment. In vivo, they are found in precise locations and orientations within biological membranes. For example, the dihydroxycarotenoids such as lutein and zeaxanthin orient themselves perpendicularly to the membrane surface as molecular rivets in order to expose their hydroxyl groups to a more polar environment. 

In humans, carotenoids were reported in liver, adrenals, testes, kidneys, lungs, skin, eyes, and adipose tissnes. Adipose tissne seems to be the main storage site, together with the liver acconnting for at least 80% of carotenoid storage. It was suggested that the tissue distribution of carotenoids may correlate with the LDL uptake in tissnes expressing LDL receptors at their surfaces, but this does not explain why some tissues show marked enrichment in specific carotenoids, i.e., the hnman macnla accumulates specifically the two xanthophylls, lutein and zeaxanthin. 

Updike, A.A. and Schwartz, S.J., Thermal processing of vegetables increases cis isomers of lutein and zeaxanthin, J. Agric. Food Chem., 51, 6184, 2003. 

Aman, R. et al.. Application of HPLC coupled with DAD, APcI-MS and NMR to the analysis of lutein and zeaxanthin stereoisomers in thermally processed vegetables. Food Chem., 92 753, 2005. 

Replacement of the hydrogen at the 3 or 3 position of the carotene ring with a hydroxyl is the next step in both branches of the pathway. Hydroxylation of the rings of the carotenes leads to biosynthesis of the xanthophylls, including the well-known lutein and zeaxanthin food pigments. Lutein is formed by hydroxylation of a-carotene zeaxanthin is formed by hydroxylation of P-carotene. 

The most common mobile phase is a gradient of petroleum ether or hexane with increasing concentrations of acetone or diethyl ether. Development of the column should be optimized for each sample to afford a quick and effective separation to avoid band broadening. The separation can be followed visually. The most non-polar a- and 3-carotenes are eluted first as a yellow band followed by the chlorophylls and other more polar carotenoids like cryptoxanthin, lutein, and zeaxanthin that frequently fuse together and appear as a single band. ... 

Figure 6.2.2 shows the separations of mixtures of standards on a monomeric C,g column and also on a polymeric C30 column. The elution order on the monomeric C18 column is, as expected, first the dihydroxy xanthophyUs (lutein and zeaxanthin), followed by the monohydroxy compounds (rubixanthin and P-cryptoxanthin), and finally by the carotenes (y-, a-, and p-carotene). However, on the C30 column, rubixanthin and y-carotene, both with 1 acyclic /-end group, eluted after a- and P-carotene, with two cyclic end groups. 

Both MS and NMR coupling to HPLC have been employed for the analysis of p-carotene isomers and determination of lutein and zeaxanthin isomers in spinach, sweet com, and in retina. Capillary high performance hquid chromatography with stop flow connected to NMR (600 MHz) was used for stracture elucidation of all-trans deoxylutein 11 and its isomers.Efforts are in progress to eliminate the remaining major drawbacks such as obligatory use of deuterated solvents in the mobile phase, poor sensitivity, and low throughput of HPLC-NMR analyses. 

Dachtler, M. et al.. Combined HPLC-MS and HPLC-NMR on-line coupling for the separation and determination of lutein and zeaxanthin stereoisomers in spinach and in retina. Anal. Chem., 73, 667, 2001. 

The food matrix including its fiber and lipid content and concentrations of other carotenoids in the diet may influence the extent of absorption of carotenoid compounds. The relative absorption of lutein from a mixed vegetable diet was lower than from a diet containing pure lutein. A mixed preparation of lutein and zeaxanthin did not influence the absorption of P-carotene. 

Dietary intake data from a number of studies in North America and the United Kingdom indicate that intake of lutein from natural sources is in the range of 1 to 2 mg/day (approximately 0.01 to 0.03 mg/kg body weight per day). Simulations considering proposed levels of use as a food ingredient resulted in an estimated mean and 90th percentile of intake of lutein plus zeaxanthin of approximately 7 and 13 mg/day, respectively. Formulations containing lutein and zeaxanthin are also available as dietary supplements, but no reliable estimates of intakes from these sources were available. 

Sujak, A., J. Gabrielska, W. Grudzinski, R. Bore, P. Mazurek, and W.I. Gruszecki. 1999. Lutein and zeaxanthin as protectors of lipid membranes against oxidative damage The structural aspects. Arch. Biochem. Biophys. 371 301-317. 

Sujak, A., W. Okulski, and W.I. Gruszecki. 2000. Organisation of xanthophyll pigments lutein and zeaxanthin in lipid membranes formed with dipalmitoylphosphatidylcholine. Biochim. Biophys. Acta 1509 255-263. 

Dachtler, M., Kohler, K., and Albert, K. 1998. Reversed-phase high-performance liquid chromatographic identification of lutein and zeaxanthin stereoisomers in bovine retina using a C30 bonded phase. J. 

The recognition of the importance of MP in maintaining the health of the retina has led to the development of a number of methods for determining its concentration in situ. These methods, necessarily noninvasive, are routinely employed in dietary supplementation studies with lutein or zeaxanthin to monitor the uptake of the carotenoids into the retina. Every method exploits the optical properties of lutein and zeaxanthin, specifically their absorbance at visible wavelengths. The detection of a light signal, modified by the carotenoids, is accomplished either by the retinal photoreceptors themselves (psychophysical methods) or by a physical detector such as a photomultiplier,... 

When carotenoids such as lutein and zeaxanthin are excited by wavelengths in the -450-550 nm range, they exhibit particularly strong resonance Raman signals that can be used to quantify the amount of carotenoid present. The application of this technique for quantifying the macular carotenoids has been developed, thereby providing another noninvasive physical method for MP measurement. A detailed description of this method is given in Chapter 6. 

Schalch, W. (2001). Possible contribution of lutein and zeaxanthin, carotenoids of the macula lutea, to reducing the risk of age-related macular degeneration A review. HKJ Ophthalmology 4 31—42. 

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