Zeaxanthin

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Zeaxanthin
Zeaxanthin
Identifiers
CAS number 144-68-3 YesY
PubChem 5280899
ChemSpider 4444421 YesY
UNII CV0IB81ORO YesY
ChEBI CHEBI:27547 YesY
Jmol-3D images Image 1
Properties
Molecular formula C40H56O2
Molar mass 568.88 g/mol
Appearance orange-red
Melting point 215.5 °C (419.9 °F; 488.6 K)
Solubility in water insol.
Related compounds
Related compounds lutein
xanthophyll
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Zeaxanthin is one of the most common carotenoid alcohols found in nature. It is important in the xanthophyll cycle. Synthesized in plants and some micro-organisms, it is the pigment that gives paprika (made from bell peppers), corn, saffron, wolfberries, and many other plants and microbes their characteristic color.[1]

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 leaves of most green 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 very high light levels, during photosynthesis.

Animals derive zeaxanthin from a plant diet. Zeaxanthin is one of the two primary xanthophyll carotenoids contained within the retina of the eye. Within the central macula, zeaxanthin is the dominant component, whereas in the peripheral retina, lutein predominates.

Zeaxanthin supplements are used to treat different disorders, mainly with affecting the eyes.[2] There are no reported side effects from taking zeaxanthin supplements. However, there is a decreased absorption rate when taken with Orlistat, mineral oil, and Chitosan.[3]

As a food additive, zeaxanthin is a food dye with E number E161h.

Isomers[edit]

Lutein and zeaxanthin have identical chemical formulas and are isomers, but they are not stereoisomers. The only difference between them is in the location of the double bond in one of the end rings. This difference gives lutein three chiral centers whereas zeaxanthin has two. Because of symmetry, the (3R,3'S) and (3S,3'R) stereoisomers of zeaxanthin are identical. Therefore, zeaxanthin has only three stereoisomeric forms. The (3R,3'S) stereoisomer is called 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.[4]

Due to the commercial value of carotenoids, their biosynthesis has been studied extensively in both natural producers, 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.[5]

Relationship with diseases of the eye[edit]

Several observational studies have connected high dietary intake of foods providing zeaxanthin with lower incidence of age-related macular degeneration (AMD), most notably the Age-Related Eye Disease study (AREDS).[6][7] There is currently insufficient evidence to assess the effectiveness of dietary or supplemental antioxidants in treatment or primary prevention of ARMD, or the formation or progression of cataracts.[6][8] Any benefit is more likely to be apparent in subpopulations of individuals exposed to high oxidative stress, such as heavy smokers or those with poor nutrition.[9] In 2005, the US Food and Drug Administration rejected a Qualified Health Claims application by Xangold, citing insufficient evidence supporting the use of a zeaxanthin-containing supplement in prevention of AMD.[10]

Natural occurrence[edit]

Zeaxanthin is one of the most common carotenoid alcohols found in nature. It is the pigment that gives paprika (made from bell peppers), corn, saffron, wolfberries, and many other plants their characteristic color.[11] Spirulina is also a rich source and can serve as a dietary supplement.[12] Zeaxanthin breaks down to form picrocrocin and safranal, which are responsible for the taste and aroma of saffron.

Foods considered good sources of lutein and zeaxanthin include eggs, spinach, goji berry (wolfberries), kale, turnip greens, collard greens, romaine lettuce, broccoli, zucchini, kiwifruit, corn, garden peas, Swiss chard and Brussels sprouts.[7]

References[edit]

  1. ^ Encyclopedia.com. "Carotenoids". Retrieved 6 May 2012. 
  2. ^ MD Support. "Study Demonstrates Essential Role of Zeaxanthin in Eye Health". Retrieved 6 May 2012. 
  3. ^ Meschino Health. "Comprehensive Guide to Lutein & Zeaxanthin". Retrieved 6 May 2012. 
  4. ^ See POLA Study
  5. ^ Scaife, Mark A.; Ma, Cynthia A.; Ninlayarn, Thanyanun; Wright, Phillip C.; Armenta, Roberto E. (22 May 2012). "Comparative Analysis of β-Carotene Hydroxylase Genes for Astaxanthin Biosynthesis". Journal of Natural Products 75 (6): 120522090507004. doi:10.1021/np300136t. PMID 22616944. 
  6. ^ a b Krishnadev N, Meleth AD, Chew EY (May 2010). "Nutritional supplements for age-related macular degeneration". Current Opinion in Ophthalmology 21 (3): 184–9. doi:10.1097/ICU.0b013e32833866ee. PMC 2909501. PMID 20216418. 
  7. ^ a b SanGiovanni JP, Chew EY, Clemons TE, et al. (September 2007). "The relationship of dietary carotenoid and vitamin A, E, and C intake with age-related macular degeneration in a case-control study: AREDS Report No. 22". Archives of Ophthalmology 125 (9): 1225–1232. doi:10.1001/archopht.125.9.1225. PMID 17846363. 
  8. ^ Chong EW, Wong TY, Kreis AJ, Simpson JA, Guymer RH (October 2007). "Dietary antioxidants and primary prevention of age related macular degeneration: systematic review and meta-analysis". BMJ (Clinical Research Ed.) 335 (7623): 755. doi:10.1136/bmj.39350.500428.47. PMC 2018774. PMID 17923720. 
  9. ^ Fernandez MM, Afshari NA (January 2008). "Nutrition and the prevention of cataracts". Current Opinion in Ophthalmology 19 (1): 66–70. doi:10.1097/ICU.0b013e3282f2d7b6. PMID 18090901. 
  10. ^ US FDA, Qualified Health Claims: Letter of Denial - Xangold Lutein Esters, Lutein, or Zeaxanthin and Reduced Risk of Age-related Macular Degeneration or Cataract Formation (Docket No. 2004Q-0180)
  11. ^ Spice Science and Technology, K. Hirasa, M. Takamasa, page 15
  12. ^ http://www.ncbi.nlm.nih.gov/pubmed/22313576

External links[edit]