Zeaxanthin

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Zeaxanthin
Structural formula of zeaxanthin
Space-filling model of the zeaxanthin molecule
Names
IUPAC name
(3R,3′R)-β,β-Carotene-3,3′-diol
Systematic IUPAC name
(1R,1′R)-4,4′-[(1E,3E,5E,7E,9E,11E,13E,15E,17E)-3,7,12,16-Tetramethyloctadeca-1,3,5,7,9,11,13,15,17-nonaene-1,18-diyl]bis(3,5,5-trimethylcyclohex-3-en-1-ol)
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
ECHA InfoCard
 100.005.125 Edit this at Wikidata
E number E161h (colours)
UNII
  • InChI=1S/C40H56O2/c1-29(17-13-19-31(3)21-23-37-33(5)25-35(41)27-39(37,7)8)15-11-12-16-30(2)18-14-20-32(4)22-24-38-34(6)26-36(42)28-40(38,9)10/h11-24,35-36,41-42H,25-28H2,1-10H3/b12-11+,17-13+,18-14+,23-21+,24-22+,29-15+,30-16+,31-19+,32-20+/t35-,36-/m1/s1 checkY
    Key: JKQXZKUSFCKOGQ-QAYBQHTQSA-N checkY
  • InChI=1/C40H56O2/c1-29(17-13-19-31(3)21-23-37-33(5)25-35(41)27-39(37,7)8)15-11-12-16-30(2)18-14-20-32(4)22-24-38-34(6)26-36(42)28-40(38,9)10/h11-24,35-36,41-42H,25-28H2,1-10H3/b12-11+,17-13+,18-14+,23-21+,24-22+,29-15+,30-16+,31-19+,32-20+/t35-,36-/m1/s1
    Key: JKQXZKUSFCKOGQ-QAYBQHTQBL
  • CC1=C(C(C[C@@H](C1)O)(C)C)/C=C/C(=C/C=C/C(=C/C=C/C=C(/C=C/C=C(/C=C/C2=C(C[C@H](CC2(C)C)O)C)\C)\C)/C)/C
Properties
C40H56O2
Molar mass 568.88 g/mol
Appearance orange-red
Melting point 215.5 °C (419.9 °F; 488.6 K)
insol.
Related compounds
Related compounds
 lutein
xanthophyll
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Zeaxanthin is one of the most common

xanthophyll cycle. Synthesized in plants and some micro-organisms, it is the pigment that gives paprika (made from bell peppers), corn, saffron, goji (wolfberries), and many other plants and microbes their characteristic color.[1][2]

The name (pronounced zee-uh-zan'-thin) is derived from

Zea mays (common yellow maize corn, in which zeaxanthin provides the primary yellow pigment), plus xanthos, the Greek word for "yellow" (see xanthophyll
).

Xanthophylls such as zeaxanthin are found in highest quantity in the

plants, where they act to modulate light energy and perhaps serve as a non-photochemical quenching agent to deal with triplet chlorophyll (an excited form of chlorophyll) which is overproduced at high light levels during photosynthesis.[3] Zeaxanthin in guard cells acts as a blue light photoreceptor which mediates the stomatal opening.[4]

Animals derive zeaxanthin from a plant diet.[2] Zeaxanthin is one of the two primary xanthophyll carotenoids contained within the retina of the eye. Zeaxanthin supplements are typically taken on the supposition of supporting eye health. Although there are no reported side effects from taking zeaxanthin supplements, the actual health effects of zeaxanthin and lutein are not proven,[5][6][7] and, as of 2018, there is no regulatory approval in the European Union or the United States for health claims about products that contain zeaxanthin.

As a

food dye with E number
E161h.

Isomers and macular uptake

meso-zeaxanthin
.

The principal natural form of zeaxanthin is (3R,3′R)-zeaxanthin. The

macula mainly contains the (3R,3′R)- and meso-zeaxanthin forms, but it also contains much smaller amounts of the third (3S,3′S) form.[8] Evidence exists that a specific zeaxanthin-binding protein recruits circulating zeaxanthin and lutein for uptake within the macula.[9]

Due to the commercial value of carotenoids, their biosynthesis has been studied extensively in both natural products and non-natural (heterologous) systems such as the bacteria Escherichia coli and yeast Saccharomyces cerevisiae. Zeaxanthin biosynthesis proceeds from beta-carotene via the action of a single protein, known as a beta-carotene hydroxylase, that is able to add a hydroxyl group (-OH) to carbon 3 and 3′ of the beta-carotene molecule. Zeaxanthin biosynthesis therefore proceeds from beta-carotene to zeaxanthin (a di-hydroxylated product) via beta-cryptoxanthin (the mono hydroxylated intermediate). Although functionally identical, several distinct beta-carotene hydroxylase proteins are known.

Due to the nature of zeaxanthin, relative to astaxanthin (a carotenoid of significant commercial value) beta-carotene hydroxylase proteins have been studied extensively.[10]

Relationship with diseases of the eye

Several

age-related macular degeneration (AMD), most notably the Age-Related Eye Disease Study (AREDS2).[11][12] Because foods high in one of these carotenoids tend to be high in the other, research does not separate effects of one from the other.[13][14]

As for cataracts, two meta-analyses confirm a correlation between high serum concentrations of lutein and zeaxanthin and a decrease in the risk of nuclear cataract, but not cortical or subcapsular cataract. The reports did not separate a zeaxanthin effect from a lutein effect.[19][20] The AREDS2 trial enrolled subjects at risk for progression to advanced age-related macular degeneration. Overall, the group getting lutein (10 mg) and zeaxanthin (2 mg) did not reduce the need for cataract surgery.[21] Any benefit is more likely to be apparent in subpopulations of individuals exposed to high oxidative stress, such as heavy smokers, alcoholics or those with low dietary intake of carotenoid-rich foods.[22]

In 2005, the US Food and Drug Administration rejected a Qualified Health Claims application by Xangold, citing insufficient evidence supporting the use of a lutein- and zeaxanthin-containing supplement in prevention of AMD.[23] Dietary supplement companies in the U.S. are allowed to sell lutein and lutein plus zeaxanthin products using dietary supplement, such as "Helps maintain eye health", as long as the FDA disclaimer statement ("These statements have not been evaluated...") is on the label. In Europe, as recently as 2014, the European Food Safety Authority reviewed and rejected claims that lutein or lutein plus zeaxanthin improved vision.[24]

Natural occurrence

Zeaxanthin is the pigment that gives

wolfberries (goji), and many other plants their characteristic colors of red, orange or yellow.[2][18] Spirulina is also a rich source and can serve as a dietary supplement.[25] Zeaxanthin breaks down to form picrocrocin and safranal, which are responsible for the taste and aroma of saffron.[26]

Dark green

mustard greens are rich in lutein[2][27] but contain little to no zeaxanthin, with the exception of scallions cooked in oil.[28] Orange bell peppers (but not green, red, or yellow) are rich in zeaxanthin.[28]

Lutein and zeaxanthin concentrations in fruits and vegetables (µg / 100 g)[28]
Food (100 g) Lutein trans (µg) Zeaxanthin trans (µg)
Spinach, cooked 12,640 0
Spinach, raw 6,603 0
Kale, cooked 8,884 0
Cilantro 7,703 0
Scallions, cooked in oil 2,488
Scallions, raw 782 0
Bell pepper, green 173 0
Bell pepper, orange 208 1,665
Bell pepper, red 0 22
Bell pepper, yellow 139 18
Cornmeal, yellow 1 531
Cornmeal, white 13 13
Corn, cooked from frozen 202 202
Tortilla, corn 276 255

Safety

An

adverse effects.[29]
As of 2016, neither the U.S. Food and Drug Administration nor the European Food Safety Authority had set a Tolerable Upper Intake Level (UL) for lutein or zeaxanthin.

References

  1. ^ Encyclopedia.com. "Carotenoids". Retrieved 6 May 2012.
  2. ^ a b c d e "Lutein + Zeaxanthin Content of Selected Foods". Linus Pauling Institute, Oregon State University, Corvallis. 2014. Retrieved 20 May 2014.
  3. S2CID 235480018
    .
  4. ISBN 978-1-108-48639-2
    .
  5. PMID 23644932.{{cite journal}}: CS1 maint: numeric names: authors list (link
    )
  6. PMID 24672708
    .
  7. PMID 24829491
    .
  8. PMID 23703634
    .
  9. PMID 20820671
    .
  10. PMID 22616944
    .
  11. ^ "NIH study provides clarity on supplements for protection against blinding eye disease". US National Eye Institute, National Institutes of Health, Bethesda, MD. 5 May 2013. Archived from the original on 15 August 2019. Retrieved 10 August 2017.
  12. PMID 26541886
    .
  13. ^
    PMID 20216418
    .
  14. PMID 17846363
    .
  15. PMID 25515572
    .
  16. S2CID 5055854
    .
  17. PMID 21899805
    .
  18. ^
    PMID 37702300
    .
  19. PMID 24451312
    .
  20. S2CID 13634941
    .
  21. PMID 23645227
    .
  22. S2CID 25735519
    .
  23. ^ "Letter of Denial - Xangold Lutein Esters, Lutein, or Zeaxanthin and Reduced Risk of Age-related Macular Degeneration or Cataract Formation (Docket No. 2004Q-0180". US FDA, Qualified Health Claims. 19 December 2005.
  24. ISSN 1831-4732
    .
  25. PMID 22313576
    .
  26. PMID 25097262
    .
  27. ^ "Foods highest in lutein-zeaxanthin per 100 grams". Conde Nast for the USDA National Nutrient Database, release SR-21. 2014. Retrieved 23 December 2015.
  28. ^
    doi:10.1016/j.jfca.2008.07.006
    . Retrieved 4 February 2024.
  29. ^
    PMID 26885380
    .
    • In their evaluation of the safety of synthetic zeaxanthin as a Novel Food, the EFSA NDA Scientific Panel [37] applied a 200-fold safety factor to this NOAEL to define an ADI of 0.75 mg/kg bw/day, or 53 mg/day for a 70 kg adult.
    • Formulated zeaxanthin was not mutagenic or clastogenic in a series of in vitro and in vivo tests for genotoxicity.
    • Information from human intervention studies also supports that an intake higher than 2 mg/day is safe, and an intake level of 20 mg/day for up to 6 months was without adverse effect.
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