Lutein

Xanthophylls have antioxidant activity and react with active oxygen species, producing biologically active degradation products. They also can inhibit peroxidation of membrane phospholipids and reduce lipofuscin formation, both of which contribute to their antioxidant properties. Lutein is naturally present in the macula of the human retina. It filters out potentially phototoxic blue light and near-ultraviolet radiation from the macula. The protective effect is due in part, to the reactive oxygen species quenching ability of these carotenoids. Lutein is more stable to decomposition by pro-oxidants than are other carotenoids such as beta-carotene and lycopene. Lutein is abundant in the region surrounding the fovea, and lutein is the predominant pigment at the outermost periphery of the macula. Zeaxanthin, which is fully conjugated (lutein is not), may offer somewhat better protection than lutein against phototoxic damage caused by blue and near-ultraviolet light radiation. Lutein is one of only two carotenoids that have been identified in the human lens, may be protective against age-related increases in lens density and cataract formation. Again, the possible protection afforded by lutein may be accounted for, in part, by its reactive oxygen species scavenging abilities. Carotenoids also provide protection from cancer. One of the mechanisms of this is by increasing the expression of the protein connexin-43, thereby stimulating gap junctional communication and preventing unrestrained cell proliferation.