Xanthophylls lutein

The degree of linkage of a compound may also affect its bioaccessibility in the gut. It is generally admitted that a compound linked with other molecules (e.g., via esterification, glycosylation, etc.) is not absorbed as well as its free form and thus it must be hydrolyzed in the gut in order to be taken up by enterocytes. Due to the presence of hydroxyl or keto groups on their molecules, the xanthophylls (lutein, zeaxanthin, and P-cryptoxanthin) are found in both free and esterified (monoester or diester) forms in nature, but few studies have been conducted to date to assess the bioavailabilities of these esters. 

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. 

Solvents with different polarities and refractive indexes significantly affect carotenoid optical properties. Because the refractive index is proportional to the ability of a solvent molecule to interact with the electric held of the solute, it can dramatically affect the excited state energy and hence the absorption maxima positions (Bayliss, 1950). Figure 7.2a shows three absorption spectra of the same xanthophyll, lutein, dissolved in isopropanol, pyridine, and carbon disulfide. The solvent refractive indexes in this case were 1.38, 1.42, and 1.63 for the three mentioned solvents, respectively. 

The v4 region enhancement and structure in the resonance Raman spectra of xanthophylls reviewed in this chapter shows that it can be used for the analysis of carotenoid-protein interactions. Figure 7.8 summarizes the spectra for all four major types of LHCII xanthophylls. Lutein 2 possesses the most intense and well-resolved v4 bands. The spectrum for zeaxanthin is very similar to that of lutein with a slightly more complex structure. This similarity correlates with the structural similarity between these pigments. It is likely that they are both similarly distorted. The richer structure of zeaxanthin spectrum may be explained by the presence of the two flexible P-end rings... 

In the eye, carotenoids occur mainly in the retina, but the xanthophylls, lutein and zeaxanthin, can also be detected in the lens and the ciliary body. The human lens contains lutein and zeaxanthin... 

C. Gartner, W. Stahl, and H. Sies, Preferential increase in chylomicron levels of the xanthophylls lutein and zeaxanthin compared to beta-carotene in the human, Int. J. Vitam. Nutr. Res. 66 (1996) 119-125. 

Oil-soluble egg-yellow colour good stability the xanthophyll lutein is a carotenoid colour which occurs in green leaves, vegetables, eggs and some flowers... 

The human body stores a variety of carotenes (lycopene, a- and (3-carotenes), as well as xanthophylls (lutein, zeaxanthin and cryptoxanthin) [38]. Besides the main naturally occurring all-E configuration, there also exist some Z-stereoi-somers of (3-carotene and lycopene in the human serum at remarkable levels, as shown in Table 5.2.2 [39,40]. 

It is conceivable that the different carotenoids have specialized functions in different tissues as has been shown for the xanthophylls lutein and zeaxanthin, which are virtually the only carotenoids occurring in the macular area of the retina. The distribution of lycopene in human tissues is shown in Table 63.2 and Table 63.3. 

Pathways. Studies of carotenoid transformations that take place when a mutant strain, PGl, of the green alga Scenedesmus obliquus is transferred from dark to light conditions have indicated that the transformations 15-cw-phytoene (180) 15-c/5-phytofluene (181) - 15-cis- -carotene (182) -> trans-C-caro-tene (183) (Scheme 7) take place in the biosynthesis of the normal cyclic carotenoids. The results were also in agreement with the formation of the xanthophylls lutein (16) and zeaxanthin (174) from the corresponding carotenes. 

Perry, A., Rasmussen, H., and Johnson E.J., Xanthophyll (lutein, zeaxanthin) content in fruits, vegetables and com and egg products, J. Food Comp. Anal., 22, 9, 2009. 

The photosynthetic pigments of higher plants comprise not only the chlorophylls (a and b) but also a range of carotenoids. The main ones of these are B-carotene (usually 25-30% of the total carotenoids) and the xanthophylls lutein (45-50%), violaxanthin (ca. 15%) and neoxanthin (ca. 15%), though small amounts of others, e.g. a-carotene, zeaxanthin, antheraxanthin, lutein-5,6-epoxide and a-cryptoxanthin, may also be detected. The... 

Ae9] Xanthophyll, Lutein SO, 94 CII1026. Zeazanthin 30, 97 0 II1026. Lupeol-cinnamat 9, 586,1231, II389. Seml-. oarotinon 30, 89. 

In addition to P-carotene, freshwater fish can also convert the xanthophyl lutein (5-12), also known as 3,3 -dihydroxy-a-carotene or (3R,3 S,6 R)-p,8-carotene-3,3 -diol, into vitamin A. Lutein eliminates one molecule of water (C-3 hydroxyl group) and yields anhydrolutein (5-13), which cleaves to the corresponding aldehydes. These aldehydes are reduced to a l-trans-3,4-didehydroretinol (vitamin A2) and aU-trans-3-hydroxyretinol, respectively. The latter compound can dehydrate to form another... 

In leafy vegetables, -carotene usually amounts to 10-20% of total carotenoid content. As in carrots, other carotenoid pigments are various xanthophylls. Lutein, violaxanthin and neoxanthin usually occur in large amounts, while cryptoxanthin, zeaxanthin (the main carotenoid of maize), antheraxanthin and other xanthophylls are found in smaller amounts (Table 9.14). The presence of carotenoids is masked by chlorophylls. Lettuce Lactuca sativa, Asteraceae) is an example of a vegetable accumulating a higher amount of lactucaxanthin. 

The main pigments of depot fats of birds (poultry) and mammals are xanthophylls lutein and zeaxanthin. Also present are small amounts of fl-carotene and other pigments. 

Xanthophylls are more specific within each class of algae. A particular xanthophyll, lutein (3,3 -dihydroxy-a-carotene), is common to aU three classes but is often in the majority in the Chlorophyceae. Two other xanthophylls are distributed among these three classes zeaxan-thin (3,3 -dihydroxy-P-carotene) in Chlorophyceae and... 

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