The retinal carotenoids zeaxanthin and lutein scavenge superoxideand hydroxyl radicals: A chemiluminescence and ESR study

[摘要] Purpose: Carotenoids are present in many biological systems, oftendecreasing the formation of products of oxidative damage to biologicalmolecules. In the macula their concentration is so high that it has beenbelieved that the yellow color filters out damaging blue light. Recentreports that dietary lutein reduces the risk of cataract in the eye lenssuggested that the antioxidant action of carotenoids, which has beeninferred from decreased oxidative damage, warranted further directinvestigation.Methods: Superoxide and hydroxyl radical scavenging by lutein andzeaxanthin (retinal carotenoids), β-carotene, lycopene, luteinesters (from marigolds), and a commercial mixture of soy carotenoidswere compared to scavenging by ascorbate and ascorbyl palmitate. Radicalscavenging was measured with a chemiluminescent assay (luminol) and byelectron spin resonance, ESR. Inhibitory concentrations, IC50,were determined with the luminescent assay.Results: All of the carotenoids scavenged both superoxide (in ESR30-50% at 16.7 μM) and hydroxyl radicals (in ESR 50-70% at 16.7 μM, in a luminescent assay 90-99%).Conclusions: While crocin may be unable to scavenge superoxide, someof the other carotenoids do so quite effectively. The mixtures of15,15'-cis and all-trans-carotenoids studied by ESR andluminescent assay scavenge both superoxide and hydroxyl radicals.Lycopene and β-carotene both scavenge superoxide more effectivelythan the xanthophylls of the retina, zeaxanthin and lutein. All of thecarotenoids examined scavenged the hydroxyl radicals more effectivelythan superoxide radicals. The predominant carotenoid in the fovea of theretina, zeaxanthin, scavenged hydroxyl radicals more effectively thanthe other retinal carotenoid, lutein. Possible mechanisms of radicalscavenging by the carotenoids are discussed.

[学科分类] 生物化学/生物物理