Structure & Function
Structure & Function Of Zeaxanthin & Lutein
Zeaxanthin and lutein are key carotenoids in the prevention of Age-Related Macular
Degeneration (AMD). Chrysantis, Inc. is the only company producing a natural, highly
concentrated zeaxanthin-lutein compound, to help prevent the damaging effects of
AMD.
Zeaxanthin and lutein are localized at the very center of the macula (the fovea)
– the part of the eye rich in rod and cone photoreceptors that gives a person
optimal visual acuity. There is 1.5 times more zeaxanthin than lutein in the inner
retina.
Animal studies have shown zeaxanthin to be very effective in protecting both cone
and rod photoreceptors. Quail fed with normal dietary levels of zeaxanthin had significantly
less retinal damage than the zeaxanthin-deprived group .
Lutein is a natural pigment found in dark leafy vegetables and various fruits, including
spinach, corn and egg yolks. Lutein helps to filter harmful blue light from the
macula and acts as an antioxidant for the retinal cells. Lutein is more abundant
in the eye than zeaxanthin, where it serves as a protector for precious photoreceptors.
Recent studies have shown that variations from the common distribution of macular
pigments in the eye may be associated with early AMD while individuals with lesions
near the foveal region (where zeaxanthin and lutein predominates) may be at a higher
risk of developing late AMD. They also show that a reduced central macular pigment
and a low central/total ratio are associated with atrophic spots and geographic
atrophy in the unaffected eye..
Analyses of macular pigment concentrations in and around the center of the macula
in eyes with AMD versus normal control eyes have shown a direct link between macular
pigment concentration and AMD. It has been observed that there is a significant
drop in pigment concentration at the edges of the fovea in eyes with AMD .
The evidence points to the importance of maintaining a stable amount of zeaxanthin
and lutein predominantly in the fovea, but also in the macular periphery and the
lens, to maintain eye health throughout our senescent years.
Zeaxanthin is 5 to 10 times less abundant than lutein in human blood serum and 10
to 20 times less prevalent in the diet. In a 2001 study, ocular tissues of human
donor eyes were tested to determine the amount of carotenoids present. The level
of lutein was found to be 2-7-fold higher than other common carotenoids, including
ß-carotene, ∞carotene and lycopene.
Because of this, the body created a compromise molecule from the more abundant lutein
– meso zeaxanthin – to complement dietary zeaxanthin and reach the levels
needed in the fovea to protect the macula from damaging blue light.
We know today that this imperfect solution (the production of meso zeaxanthin) falters
as we age , resulting in lower levels of macular
pigment concentration.
A zeaxanthin-lutein supplement will definitively reduce the need for this ‘zeaxanthin-like’
molecule, thus ensuring long lasting eye protection.
Typical dietary zeaxanthin and lutein intake averages 2 milligrams per day. Various
epidemiological studies have found an association between supplemental intake of
zeaxanthin and lutein (around 6 milligrams per day) and a decreased risk in AMD
and cataracts, thus suggesting a dietary gap
of 4 milligrams per day. This dietary gap is greater for people age 50 and older
as their dietary carotenoid intake is significantly lower than the average adult.
Dietary supplements are an important way to compensate for the low levels of zeaxanthin
and lutein in food intake and provide the eye with the necessary amount to reduce
the risk and/or prevent AMD from developing.
Dietary supplements for eye health should contain at least equal amounts of zeaxanthin
and lutein per capsule, since zeaxanthin and its isomers represent 50 percent of
the carotenoids present in the human retina.
Zeaxanthin is a 40 carbon long molecule, with 11 conjugated double bonds. Its molecular
formula is CHO and has a molecular weight of 568.88 daltons. Zeaxanthin
exists in three stereoisomeric forms that result from the configurations at its
two chiral centers: the (3R,3’R), (3R,3’S) and (3S,3’S). The principal
natural form of zeaxanthin is the (3R, 3’R).
Chrysantis’ marigolds produce only 3R,3’R zeaxanthin.
A three-dimensional view of zeaxanthin shows it to be a straight molecule that is
able to transverse a biological cell membrane because of its hydrophilic end groups
and lipophilic central chain. It tends to span the bilipid layer occupying a site
that lies perpendicular to the membrane surface, while lutein apparently inserts
itself in a non-orthogonal manner. Thus, zeaxanthin is in position to act as a membrane
antioxidant.
Lutein’s molecular formula is CHO and has a molecular weight of 644 daltons. Both
substances have the same number of double bonds, however, the position of the double
bond in lutein forms a more chemically reactive allylic hydroxyl end group versus
the extra conjugated double bond in zeaxanthin. Zeaxanthin has a better protective
ability than lutein because of its greater conjugated, symmetrical structure.
Lutein and zeaxanthin are thought to orient themselves so they can span cell membranes
inside the lipid bi-layer in the eye, increasing membrane stability. It is because
of their antioxidant capacity and ability to filter out potentially phototoxic blue
light and near ultraviolet radiation that zeaxanthin and lutein are believed to
play an important role in protection against Age-Related Macular Degeneration (AMD)
and age-related cataract formation . Risks of
developing AMD have been found to be significantly higher in people with lower plasma
concentrations of zeaxanthin and lutein.
The body selectively places dietary zeaxanthin and lutein in the very center of
the macula – the most critical area for central vision with the greatest need
for protection. These substances also accumulate in the retinal pigmented epithelium
and the most vulnerable portions of photoreceptors, where its potent antioxidant
capacity can prevent oxidative damage. However, the overall distribution of zeaxanthin
in the eye suggests that it has a specific function, separate from lutein.
The human lens also accumulates zeaxanthin (although it is one of the most metabolically
inactive tissues in the body) where, along with lutein, may protect against aged-related
increases in lens density and cataract formation .
|