Lutein

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Lutein
Luteine - Lutein.svg
Space-filling model of lutein
Names
IUPAC name
β,ε-carotene-3,3'-diol
Other names
Luteine; trans-lutein; 4-​[18-​(4-​Hydroxy-​2,6,6-​trimethyl-​1-​cyclohexenyl)-​3,7,12,16-​tetramethyloctadeca-​1,3,5,7,9,11,13,15,17-​nonaenyl]-​3,5,5-​trimethyl-​cyclohex-​2-​en-​1-​ol
Identifiers
127-40-2 YesY
ChEBI CHEBI:28838 YesY
ChEMBL ChEMBL173929 YesY
ChemSpider 4444655 YesY
Jmol 3D model Interactive image
PubChem 5281243
UNII X72A60C9MT YesY
  • 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/h11-25,35-37,41-42H,26-28H2,1-10H3/b12-11+,17-13+,18-14+,23-21+,24-22+,29-15+,30-16+,31-19+,32-20+/t35-,36+,37-/m0/s1 YesY
    Key: KBPHJBAIARWVSC-RGZFRNHPSA-N YesY
  • 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/h11-25,35-37,41-42H,26-28H2,1-10H3/b12-11+,17-13+,18-14+,23-21+,24-22+,29-15+,30-16+,31-19+,32-20+/t35-,36+,37-/m0/s1
    Key: KBPHJBAIARWVSC-RGZFRNHPBY
  • Key: KBPHJBAIARWVSC-RGZFRNHPSA-N
  • 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)/C=C/[C@H]2C(=C[C@@H](CC2(C)C)O)C)/C)/C
Properties
C40H56O2
Molar mass 568.871 g/mol
Appearance Red-orange crystalline solid
Melting point 190 °C (374 °F; 463 K)[1]
Insoluble
Solubility in fats Soluble
Vapor pressure {{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY verify (what is YesYN ?)
Infobox references

Lutein (/ˈluːtiː.ᵻn/ or /ˈluːtiːn/;[2] from Latin luteus meaning "yellow") is a xanthophyll and one of 600 known naturally occurring carotenoids. Lutein is synthesized only by plants and like other xanthophylls is found in high quantities in green leafy vegetables such as spinach, kale and yellow carrots. In green plants, xanthophylls act to modulate light energy and serve as non-photochemical quenching agents to deal with triplet chlorophyll (an excited form of chlorophyll), which is overproduced at very high light levels, during photosynthesis. See xanthophyll cycle for this topic.

Lutein is obtained by animals directly or indirectly, from plants. Lutein is apparently[citation needed] employed by animals as an antioxidant and for blue light absorption. Lutein is found in egg yolks and animal fats. In addition to coloring yolks, lutein causes the yellow color of chicken skin and fat, and is used in chicken feed for this purpose. The human retina accumulates lutein and zeaxanthin. The latter predominates at the macula lutea while lutein predominates elsewhere in the retina. There, it may serve as a photoprotectant for the retina from the damaging effects of free radicals produced by blue light. Lutein is isomeric with zeaxanthin, differing only in the placement of one double bond.

The principal natural stereoisomer of lutein is (3R,3′R,6′R)-beta,epsilon-carotene-3,3′-diol. Lutein is a lipophilic molecule and is generally insoluble in water. The presence of the long chromophore of conjugated double bonds (polyene chain) provides the distinctive light-absorbing properties. The polyene chain is susceptible to oxidative degradation by light or heat and is chemically unstable in acids.

Lutein is present in plants as fatty-acid esters, with one or two fatty acids bound to the two hydroxyl-groups. For this reason, saponification (de-esterfication) of lutein esters to yield free lutein may yield lutein in any ratio from 1:1 to 1:2 molar ratio with the saponifying fatty acid.

As a pigment

This xanthophyll, like its sister compound zeaxanthin, has primarily been used as a natural colorant due to its orange-red color. Lutein absorbs blue light and therefore appears yellow at low concentrations and orange-red at high concentrations. Lutein is also anti angiogenic. It inhibits vascular endothelial growth factor (VEGF).

Lutein was traditionally used in chicken feed to improve the color of broiler chicken skin. Polled consumers viewed yellow chicken skin more favorably than white chicken skin. Such lutein fortification also results in a darker yellow egg yolk. Today the coloring of the egg yolk has become the primary reason for feed fortification. Lutein is not used as a colorant in other foods due to its limited stability, especially in the presence of other dyes.

Role in human eyes

Lutein was found to be concentrated in the macula, a small area of the retina responsible for central vision. The hypothesis for the natural concentration is that lutein helps keep the eyes safe from oxidative stress and the high-energy photons of blue light. Various research studies have shown that a direct relationship exists between lutein intake and pigmentation in the eye.[3][4][5][6][7][8][9]

Lutein may play a role in Haidinger's brush, an entoptic phenomenon that allows humans to detect polarized light.

Macular degeneration

Several studies show that an increase in macula pigmentation decreases the risk for eye diseases such as age-related macular degeneration (AMD).[10][11][12] The only randomized clinical trial to demonstrate a benefit for lutein in macular degeneration was a small study, in which the authors concluded that visual function is improved with lutein alone or lutein together with other nutrients and also that more study was needed.[11]

There is epidemiological evidence of a relationship between low plasma concentrations of lutein and zeaxanthin, and an increased risk of developing age-related macular degeneration (AMD). Some studies support the view that supplemental lutein and/or zeaxanthin help protect against AMD.[13]

In 2007, in a six-year study, John Paul SanGiovanni of the National Eye Institute, Maryland, found that lutein and zeaxanthin protect against blindness (macular degeneration), affecting 1.2 million Americans, mostly after age 65. Lutein and zeaxanthin reduce the risk of AMD.[13]

In 2013, findings of the Age-related Eye Disease Study 2 were reported in JAMA; AREDS2 was a five-year study designed to test whether the original AREDS formulation that was shown to reduce progression of age-related macular degeneration by 25 percent would be improved by adding omega-3 fatty acids; adding lutein and zeaxanthin; removing beta-carotene; or reducing zinc.[14] In AREDS2, participants took one of four AREDS formulations: the original AREDS formulation, AREDS formulation with no beta-carotene, AREDS with low zinc, AREDS with no beta-carotene and low zinc.[14] In addition, they took one of four additional supplement or combinations including lutein and zeaxanthin (10 mg and 2 mg), omega-3 fatty acids (1,000 mg), lutein/zeaxanthin and omega-3 fatty acids, or placebo.[14] The study reported that there was no overall additional benefit from adding omega-3 fatty acids or lutein and zeaxanthin to the formulation.[14] However, the study did find benefits in two subgroups of participants: those not given beta-carotene, and those who had very little lutein and zeaxanthin in their diets.[14] Removing beta-carotene did not curb the formulation's protective effect against developing advanced AMD, which was important given that high doses of beta-carotene had been linked to higher risk of lung cancers in smokers.[14] It was recommended to replace beta-carotene with lutein and zeaxanthin in future formulations for these reasons.[14]

Cataracts

There is also epidemiological evidence that increasing lutein and zeaxanthin intake lowers the risk of cataract development.[13][15] Consumption of more than 2.4 mg of lutein/zeaxanthin daily from foods and supplements was significantly correlated with reduced incidence of nuclear lens opacities, as revealed from data collected during a 13- to 15-year period in the Nutrition and Vision Project (NVP).[16]

Photophobia (abnormal human optical light sensitivity)

A study by Stringham and Hammond, published in the January/February 2010 issue of Journal of Food Science, discusses the improvement in visual performance and decrease in light sensitivity (glare) in subjects taking 10 mg lutein and 2 mg zeaxanthin per day.[17]

In nutrition

Lutein is a natural part of human diet when fruits and vegetables are consumed. For individuals lacking sufficient lutein intake, lutein-fortified foods are available, or in the case of elderly people with a poorly absorbing digestive system, a sublingual spray is available. As early as 1996, lutein has been incorporated into dietary supplements. While no recommended daily allowance currently exists for lutein as for other nutrients, positive effects have been seen at dietary intake levels of 6–10 mg/day.[18] The only definitive side effect of excess lutein consumption is bronzing of the skin (carotenodermia).

The functional difference between lutein (free form) and lutein esters is not entirely known. It is suggested that the bioavailability is lower for lutein esters, but much debate continues.[19]

As a food additive, lutein has the E number E161b (INS number 161b) and is extracted from the petals of marigold (Tagetes erecta).[20] It is approved for use in the EU[21] and Australia and New Zealand[22] but is banned in the USA.[citation needed]

Some foods are considered good sources of the nutrients:[13][23][24][25]

Product Lutein/zeaxanthin (micrograms per hundred grams)
nasturtium (yellow flowers, lutein levels only) 45,000
kale (raw) 39,550
kale (cooked) 18,246
dandelion leaves (raw) 13,610
nasturtium (leaves, lutein levels only) 13,600
turnip greens (raw) 12,825
spinach (raw) 12,198
spinach (cooked) 11,308
swiss chard (raw or cooked) 11,000
turnip greens (cooked) 8440
collard greens (cooked) 7694
watercress (raw) 5767
garden peas (raw) 2593
romaine lettuce 2312
zucchini 2125
brussels sprouts 1590
pistachio nuts 1205
broccoli 1121
carrot (cooked) 687
Maize/corn 642
egg (hard boiled) 353
avocado (raw) 271
carrot (raw) 256
kiwifruit 122

Commercial value

The lutein market is segmented into pharmaceutical, nutraceutical, food, pet foods, and animal and fish feed.

  • The pharmaceutical market is estimated to be about US$190 million, nutraceutical and food is estimated to be about US$110 million.
  • Pet foods and other applications are estimated at US$175 million annually.

Apart from the customary age-related macular degeneration applications, newer applications are emerging in cosmetics, skin care area as an antioxidant. It is one of the fastest growing areas of the US$2 billion carotenoid market.[26]

See also

References

  1. ↑ MSDS at Carl Roth (Lutein Rotichrom, German).
  2. ↑ "lutein", Random House Webster's Unabridged Dictionary.
  3. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Landrum, J., et al. Serum and macular pigment response to 2.4 mg dosage of lutein. in ARVO. 2000.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ 11.0 11.1 Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ 13.0 13.1 13.2 13.3 Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 14.6 http://www.nei.nih.gov/news/pressreleases/050513.asp
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ WHO/FAO Codex Alimentarius General Standard for Food Additives
  21. ↑ UK Food Standards Agency: Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ Australia New Zealand Food Standards CodeLua error in package.lua at line 80: module 'strict' not found.
  23. ↑ Reuters, Study finds spinach, eggs ward off cause of blindness
  24. ↑ USDA National Nutrient Database for Standard Reference, Release 23 (2010)
  25. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  26. ↑ FOD025C The Global Market for Carotenoids, BCC Research

External links

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