Xanthophyll esters

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. 

Chitchumroonchokchai, C. and Failla, M.L., Hydrolysis of zeaxanthin esters by carboxyl ester lipase during digestion facilitates micellarization and uptake of the xanthophylls by Caco-2 human intestinal cells, J. Nutr., 136, 588, 2006. 

Conversion of xanthophyll esters to free xanthophylls in marigold using methanol... 

Extraction of total xanthophyll esters from marigold in hydrocarbon solvent, removal of impurities and cis-isomers by alcohol washing and concentration of trans-esters... 

Marigold petals are rich sources of xanthophyUs, mainly lutein esters. To increase the coloring power, chemical extraction of the colorant from flower meal is performed or a new enzymatic procedure is applied. It was shown that treatment with cellulases or mixed saprophyte microorganisms or solid state fermentation improved the xanthophyll extraction yield. ... 

Alkaline hydrolysis (saponification) has been used to remove contaminating lipids from fat-rich samples (e.g., pahn oil) and hydrolyze chlorophyll (e.g., green vegetables) and carotenoid esters (e.g., fruits). Xanthophylls, both free and with different degrees of esterification with a mixture of different fatty acids, are typically found in fruits, and saponification allows easier chromatographic separation, identification, and quantification. For this reason, most methods for quantitative carotenoid analysis include a saponification step. 

However, complete hydrolysis of carotenoid esters sometimes is not achieved in 1 to 3 hr. The saponification degree can be verified easily by the presence of carotenol ester peaks eluting later than the peaks of P-carotene on reversed phase columns. Retinol palmitate, added as an internal standard to orange juice, also serves to indicate whether saponification is complete, since it is converted to retinol which elutes at lower retention time. The mixture is subsequently washed with water until free of alkali in a separatory funnel. Other more polar solvents such as CH2CI2 or EtOAc, and diethyl ether alone or mixtured with petroleum ether can be used to increase the recovery of polar xanthophylls from the water phase. 

Gregory, G.K. et ah. Quantitative analysis of lutein esters in marigold flowers (Tagetes erecta) by high performance liquid chromatography, J. Food ScL, 51, 1093, 1986. Livingston, A.L., Rapid analysis of xanthophyll and carotene in dried plant materials, J. AOAC, 69, 1017, 1986. 

Gau, W. et ah. Mass spectrometric identification of xanthophyll fatty acid esters from marigold flowers (Tagetes erecta) obtained by high performance liquid chromatography and Craig countercurrent distribution, J. Chromatogr., 262, 277, 1983. 

Ornelas-Paz JJ, Yahia EM and Gardea A. 2007. Identification and quantification of xanthophyll esters, carotenes and tocopherols in the fruit of seven Mexican mango cultivars by liquid chromatography-APcI+-time of flight mass spectrometry. J Agric Food Chem 55 6628-6635. 

Yellow or orange fruits, including pumpkins, oranges, and peaches, which primarily contain xanthophyll esters... 

In the enterocyte, provitamin A carotenoids are immediately converted to vitamin A esters. Carotenoids, vitamin A esters, and other lipophilic compounds are packaged into chylomicrons, which are secreted into lymph and then into the bloodstream. Chylomicrons are attacked by endothelial lipoprotein lipases in the bloodstream, leading to chylomicron remnants, which are taken up by the liver (van den Berg and others 2000). Carotenoids are exported from liver to various tissues by lipoproteins. Carotenes (such as (3-carotene and lycopene) are transported by low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL), whereas xanthophylls (such as lutein, zeax-anthin, and (3-cryptoxanthin) are transported by high-density lipoproteins (HDL) and LDL (Furr and Clark 1997). 

Xanthophyll esters are common in fruits and vegetables. Few data exist regarding the effect of carotenoid esterification on carotenoid bioavailability. Xanthophyll esters are readily broken in the human intestine (West and Castenmiller 1998 Breithaupt and others 2003 Faulks and Southon 2005). Chitchumroonchokchai and Failla (2006) demonstrated that hydrolysis of zeaxanthin esters increases zeaxanthin bioavailability. Wingerath and others (1995) did not find (3-cryptoxanthin esters in chylomicrons from humans fed with tangerine juice. Herbst and others (1997) demonstrated that lutein diesters are more bioavailable than free lutein. However, the question of whether the free or the esterified form is more bioavailable to humans is still an ongoing discussion. 

For direct extraction of food samples that do not contain xanthophyll esters, chlorophylls, or have a low lipid and high carotenoid content (e.g., carrots) lb. Homogenize 5 g of ground sample with 10% (w/w) magnesium carbonate and 25 ml of 50 50 methanol/THF. 

Lyophilized and dry samples should be reconstituted with water prior to extraction. They may require saponification if the samples contain chlorophylls or xanthophyll esters. Beadlet materials should be suspended in hot water, saponified, or enzymatically hydrolyzed before extraction. Follow the manufacturer s recommendations before analyzing by HPLC. 

For saponification of food samples containing xanthophyll esters, chlorophylls, or high... 

Under these conditions, chlorophylls a and b, carotenoids, and xanthophyll esters are transferred to the epiphase (upper phase), as described in German in Lichtenthaler and Pfister (1978) and briefly in English in Lichtenthaler (1987). 

Water-containing plant materials need to be extracted with polar solvents such as acetone, methanol, or ethanol that can take up water. Freeze-dried plant tissues and freeze-dried juices can be directly extracted with diethyl ether, which contains traces of water and is more polar than light petrol or hexane. Pure light petrol or hexane are less suitable, because more polar pigments, such as Chi b or xantho-phylls, are only partially extracted from freeze-dried plant samples. A few drops of acetone or ethanol added to light petrol or hexane will, however, guarantee a complete extraction. This mixture will extract Chi a, Chi b, and all carotenoids—including xanthophyll esters and secondary carotenoids that are present in many fruits and juices—from the freeze-dried plant material. 

Saponification causes a significant loss of xanthophylls, even when carried out under relatively mild conditions (ambient temperature for 3 h) (21). In addition, several different saponification procedures have been shown to promote the formation of cis isomers of /3-carotene (74). Since saponification prolongs the analysis and is error prone, it should be carried out only when needed, as in high-fat samples or those containing carotenol esters. 

Kimura et al. (74) recommended a procedure in which the carotenoids are dissolved in petroleum ether, an equal volume of 10% methanolic KOH is added, and the mixture is left standing overnight (about 16 h) in the dark at room temperature. This treatment caused no loss or isomerization of /3-carotene, while completely hydrolyzing /3-cryptoxanthin ester. Losses of xanthophylls could be reduced to insignificant levels by using an atmosphere of nitrogen or an antioxidant. 

In general, RP-HPLC has been applied successfully to the qualitative and quantitative estimation of carotenes (64), xanthophylls, cis- and trans-carotenoids (54,60), and carotenoid fatty acid esters (53,65). Figure 5 shows an HPLC separation of (A) paprika extract, containing carotenoid esters, and (B) saponified paprika extract, containing the corresponding carotenoids (74a). 

Lutein (a-carotene-3,3 -dioI, xanthophyll) [127-40-2] M 568.9, m 196 , 1750 (423nm), 2560 (446nm), 2340 (477.5nm) in EtOH . ax > > 2 446, 479 and 511nm. Crystd from MeOH (copper-coloured prisms) or from diethyl ether by adding MeOH. Also purified by chromatography on columns of magnesia or calcium hydroxide, and crystd from CS2/EtOH. May be purified via the dipalmitate ester. Stored in the dark, in an inert atmosphere. 

Paprika oleoresin (E 160(c)) is an orange-red oil-soluble extract from sweet red peppers Capsicum annum. The major coloring compounds are xanthophylls cap-santhin (Formula 9.8), capsorubin as their dilaurate esters, and P-carotene. The presence of characteristic flavoring and spicy pungency components limits application of this extract in foodstuffs. 

Distributions of carotenoids can be characteristic for various groups of photosynthetic organisms. Fucoxan-thin is characteristic of diatoms (BaciUariophyceae) and peridinin is found in many dinoflagellates (Dinophyceae Fig. 2.23). In contrast, diatoxanthin and diadinoxanthin occur in many phytoplanktonic classes due to their xanthophyll cycle role (Fig. 2.25).Although it is a less specific marker compound, (3-carotene is abundant in cyanobacteria. Photosynthetic bacteria produce acyclic and aromatic carotenoids (e.g. lycopene and okenone, respectively Fig. 2.23). Astaxanthin and its esters are major constituents of marine zooplankton (Fig. 2.23). 

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