Lutein carotenoid interactions

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 lag-phase measurement at 234 nm of the development of conjugated dienes on copper-stimulated LDL oxidation is used to define the oxidation resistance of different LDL samples (Esterbauer et al., 1992). During the lag phase, the antioxidants in LDL (vitamin E, carotenoids, ubiquinol-10) are consumed in a distinct sequence with a-tocopherol as the first followed by 7-tocopherol, thereafter the carotenoids cryptoxanthin, lycopene and finally /3-carotene. a-Tocopherol is the most prominent antioxidant of LDL (6.4 1.8 mol/mol LDL), whereas the concentration of the others 7-tocopherol, /3-carotene, lycopene, cryptoxanthin, zea-xanthin, lutein and phytofluene is only 1/10 to 1/300 of a-tocopherol. Since the tocopherols reside in the outer layer of the LDL molecule, protecting the monolayer of phospholipids and the carotenoids are in the inner core protecting the cholesterylesters, and the progression of oxidation is likely to occur from the aqueous interface inwards, it seems reasonable to assign to a-tocopherol the rank of the front-line antioxidant. In vivo, the LDL will also interact with the plasma water-soluble antioxidants in the circulation, not in the artery wall, as mentioned above. 

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... 

Selvaraj, RK, Koutsos, EA, Calvert, CC, and Klasing, KC, 2006. Dietary lutein and fat interact to modify macrophage properties in chicks hatched from carotenoid deplete or replete eggs. J Anim Physiol Anim Nutr (Berl) 90, 70-80. 

In systems where several carotenoids are involved, the absorption of each carotenoid is governed by interactions among them carotenoids compete for absorption (Furr and Clark 1997). For example, (3-carotene supplementation reduced absorption of dietary lutein and lycopene in humans (Micozzi and others 1992). Tyssandier and others (2002) found that the absorption of dietary lycopene was reduced when a portion of spinach or pills of lutein were additionally administered to the volunteers. Similarly, the absorption of dietary lutein was reduced by consumption of tomato puree or lycopene pills (Tyssandier and others 2002). Furusho and others (2000) demonstrated that liver retinol accumulation in Wistar rats was significantly reduced when a fixed amount of (3-carotene was replaced by a mixture of (3- and a-carotene, suggesting that each one of these carotenoids mutually inhibits the utilization of the other. The proportion of (3-and a-carotene in the mixture used in that study (Furusho and others 2000) simulated that of carrots. 

Reversed-phase liquid chromatography shape-recognition processes are distinctly limited to describe the enhanced separation of geometric isomers or structurally related compounds that result primarily from the differences between molecular shapes rather than from additional interactions within the stationary-phase and/or silica support. For example, residual silanol activity of the base silica on nonend-capped polymeric Cis phases was found to enhance the separation of the polar carotenoids lutein and zeaxanthin [29]. In contrast, the separations of both the nonpolar carotenoid probes (a- and P-carotene and lycopene) and the SRM 869 column test mixture on endcapped and nonendcapped polymeric Cig phases exhibited no appreciable difference in retention. The nonpolar probes are subject to shape-selective interactions with the alkyl component of the stationary-phase (irrespective of endcapping), whereas the polar carotenoids containing hydroxyl moieties are subject to an additional level of retentive interactions via H-bonding with the surface silanols. Therefore, a direct comparison between the retention behavior of nonpolar and polar carotenoid solutes of similar shape and size that vary by the addition of polar substituents (e.g., dl-trans P-carotene vs. dll-trans P-cryptoxanthin) may not always be appropriate in the context of shape selectivity. 

Infrared and Resonance Raman Spectroscopy. Reviewson the uses of resonance Raman spectroscopy in biochemistry and biology include sections on carotenoproteins, visual pigments, and bacteriorhodopsin. The resonance Raman spectrum of the lowest excited triplet state of /3-carotene has been reported.A resonance Raman method has been used for the quantitative analysis of /3-carotene and lutein (20) in tobacco.The mechanism of carotenoid-protein interactions in the carotenoproteins ovoverdin and /3-crustacyanin has been investigated by resonance Raman spectroscopy. " 2 axanthin (24) has been used as a resonance Raman probe of membrane structure. " The resonance Raman spectra have been reported of all-frans-anhydrovitamin A (194), " /3-ionone, retinals, and Schiff bases.The technique has been used extensively to study... 

Abbreviations 77DH - 7,7-dihydro-/S-carotene (7,8-Dihydro-8, 7-i 1i o-/3,/3-carotene) ARMD - age-related macular degeneration AscHj - ascorbic acid ASTA - astaxantiiin CAR -carotenoid /J-CAR - /3-carotene ENDOR - electron nuclear double resonance epp - erythropoietic protoporphyria EPR -electron paramagnetic resonance EUR - Eourier transform infrared LUT - lutein LYC - lycopene MO/Cl - molecular orbital/charge interaction TOH-vitamin E TX-lOO-Triton X-100 ZEA - zeaxanthin... 

There is much current debate about the relevance of such carotenoid repair processes to hydrocarbon carotenoids such as 8-carotene and lycopene in vivo where the parent carotenoid is unhkely to encounter the polar ascorbic acid. However, the cation radical, with a positive charge, maybe sufficiently polar and long-lived for such interactions to be possible. For the carotenoids found in the macula, where an efficient anti-oxidant process is crucial, the hydroxy carotenoids zeaxanthin, meso zeaxanthin and lutein are likely to be in a membrane orientation such that the corresponding cation radicals are efficiently repaired by the vitamin C (cf. vitamin E, below). 

Chemical synthesis has a major part to play in the sophisticated interdisciplinary studies that are now needed to study the biological functions and actions of carotenoids, and the interactions of carotenoids with other molecules such as proteins. Essential roles in photosynthesis have been discovered for several different carotenoids, including specific geometrical isomers. Synthesis is able to provide the pure and, when appropriate, isotopically labelled carotenoids that are required for reconstitution studies, investigation of photochemistry, etc. In the field of medicine it is now clear that the provitamin A activity of p,p-carotene (3) may not be the only beneficial effect of carotenoids. Several carotenoids found in the human diet, especially lycopene (31), lutein (133) and zeaxanthin (119), could also be important in giving protection against serious disorders such as cancer, heart disease, and degenerative eye diseases. Characterization of these effects and elucidation of the mechanisms involved require substantial quantities (g to kg) of pure carotenoids these materials can only be produced by chemical synthesis. 

Human blood plasma contains mainly all-tram forms of the common dietary carotenoids but 5-cis-lycopene (up to 50% of the total plasma lycopene) and 9-cis- and 9 -cis-lutein and 9-cis-P-carotene (Khachik etal. 1992) are also commonly found. In some cases 5-cis-lycopene appears in plasma in a much greater proportion than in the food (Schierle et al. 1997). This could suggest that the 5-cis-lycopene is preferentially absorbed, or less rapidly cleared from the plasma, or that all-tram-lycopene undergoes isomerization as a result of some biochemical interaction. Simulated digestion in vitro does not cause significant acid-catalysed isomerization. 

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