Lutein absorption

Reboul, E, Thap, S, Toumiaire, F, Andre, M, Juhel, C, Morange, S, Amiot, MJ, Lairon, D, and Borel, P, 2007b. Differential effect of dietary antioxidant classes (carotenoids, polyphenols, vitamins C and E) on lutein absorption. Br J Nutr 97, 440-446. 

The presence of other carotenoids can affect the absorption of carotenoids into intestinal mucosal cells, since carotenoids can compete for absorption or facilitate the absorption of another. Data on carotenoid interactions are not clear. Human studies show that /3-carotene decreases lutein absorption, while lutein has either no effect or a lowering effect on /3-carotene absorption. Although not confirmed in humans, the inhibitory effect of lutein on /3-carotene absorption might be partly attributed to the inhibition of the /3-carotene cleavage enzyme by lutein shown in rats. Beta-carotene also seemed to lower absorption of canthaxanthin, whereas canthaxanthin did not inhibit /3-carotene absorption. Studies showed that /3-carotene increased lycopene absorption, although lycopene had no effect on /3-carotene. Alpha-carotene and cryptoxanthin show high serum responses to dietary intake compared to lutein. In addition, cis isomers of lycopene seem to be more bioavailable than the -trans, and selective intestinal absorption of a)X-trans /3-carotene occurs, as well as conversion of the 9-cis isomer to sW-trans /3-carotene. It is clear, then, that selective absorption of carotenoids takes place into the intestinal mucosal cell. 

The maximum spectrometric absorption of lutein (C40H56O2, mol wt 568.9, xanthophyll, (3R,3.S,6.R)-p,8-carotene-3,3.-diol) is found between 453 and 481 nm. Its solubihty in ethanol is greater than that of the carotenoids. It is somewhat less sensitive to oxidation and heat degradation than P-carotene. It contributes yellow color." ... 

Dietary fats, libers, and other carotenoids have been reported to interfere with carotenoid bioaccessibility. It is clear that by their presence in the gut, lipids create an environment in favor of hydrophobic compounds such as carotenoids. When arriving in the small intestinal lumen, dietary fats stimulate bile flow from the gallbladder and therefore enhance the micelle formation, which in turn could facilitate the emulsification of carotenoids into lipid micelles. Without micelle formation, carotenoids are poorly absorbed a minimum of 3 g of fat in meal is necessary for an efficient absorption of carotenoids, except for lutein esters that require higher amounts of fat. ... 

Kostic, D., White, W.S., and Olson, J.A., Intestinal absorption, serum clearance, and interactions between lutein and 3-carotene when administered to human adults in separate or combined oral doses. Am. J. Clin. Nutr, 62, 604, 1995. 

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. 

As has been pointed out earlier in this chapter, the dietary consumption and historical medicinal use of carotenoids has been well documented. In the modern age, in addition to crocin, 3.7, and norbixin, 3.8, several carotenoids have become extremely important commercially. These include, in particular, astaxanthin, 3.6 (fish, swine, and poultry feed, and recently human nutritional supplements) lutein, 3.4, and zeaxanthin, 3.3 (animal feed and poultry egg production, human nutritional supplements) and lycopene, 3.2 (human nutritional supplements). The inherent lipophilicity of these compounds has limited their potential applications as hydrophilic additives without significant formulation efforts in the diet, the lipid content of the meal increases the absorption of these nutrients, however, parenteral administration to potentially effective therapeutic levels requires separate formulation that is sometimes ineffective or toxic (Lockwood et al. 2003). 

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. 

FIGURE 7.2 (a) Absorption spectra of lutein dissolved in isopropanol (1), pyridine (2), and carbon disulfide... 

FIGURE 7.4 Absorption (a) and resonance Raman (b) spectra of the four major xanthophylls of I.HCII antenna zeaxanthin (Zea), lutein (Lut), violaxanthin (Vio), and neoxanthin (Neo). 

Absorption and Raman analysis of LHCII complexes from xanthophyll biosynthesis mutants and plants containing unusual carotenoids (e.g., lactucoxanthin and lutein-epoxide) should also be interesting, since the role of these pigments and their binding properties are unknown. Understanding the specificity of binding can help to understand the reasons for xanthophyll variety in photosynthetic antennae and aid in the discovery of yet unknown functions for these molecules. 

Zsila, F., Z. Bikadi, Z. Keresztes, J. Deli, and M. Simonyi. 2001b. Investigation of the self-organization of lutein diacetate by electronic absorption, circular dichroism spectroscopy, and atomic force microscopy. J. Phys. Chem. B 105 9413-9421. 

The contribution of lutein and zeaxanthin to the risk reduction of AMD is mainly based on two properties of the xanthophylls one is their blue-light absorption and the other is their antioxidant... 

Reboul et al., 2007a,b). As mentioned earlier the competitive uptake occurs also in the presence of a mixture of carotenoids where absorption of lutein is inhibited by [1-carotene but not by lycopene (Reboul et al., 2005). This indicates that the presence of a mixture of different lipophilic substrates can strongly influence the uptake of certain carotenoids. It has also been demonstrated that cultured Caco-2 cells secrete (3-carotene, preferentially within micelles rich in long fatty acids (Yonekura et al., 2006), suggesting that carotenoids can be stored in the cell or secreted depending on the absence or presence of appropriate carotenoid acceptors. 

SR-BI involvement in lutein uptake by Caco-2 cells and by the inhibition of [1-C absorption in the SR-BI null mouse (van Bennekum et al., 2005). 

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