Zeaxanthin

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.

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 the Greek word for yellow (see xanthophyll).

Zeaxanthin is important in the xanthophyll cycle. It is one of the most common carotenoid alcohols found in nature. It is the pigment that gives paprika (made from bell peppers), corn, saffron, and many other plants their characteristic color.

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

Isomers

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 and 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.

Relationship with diseases of the eye

Several......
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