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 .
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