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J.S. Hurst, F.J. van Kuijk; Macular Pigment Stability after Exposure to Heat and Tobacco Smoke . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1789.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare the stability and susceptibility to autoxidation of the macular pigment carotenoids, lutein and zeaxanthin, to the non polar carotenoids, lycopene and ß-carotene, after exposure to heat and whole tobacco smoke. Smoking has been recognized as a major risk factor for age-related ocular diseases such as cataract and age-related macular degeneration. Lower carotenoid plasma levels in smokers have been associated with degenerative ocular and non-ocular pathologies. Methods: Carotenoids (2-6 µM) dissolved in methanol, dichloromethane (DCM), and tetrahydrofuran (THF) were incubated at 37 and 80o C for different times. The concentrations of the carotenoids were determined spectrophotometrically from their maximum optical densities. In addition, human plasma samples were subjected to the same conditions and the carotenoids were extracted in hexane and quantitated using high performance liquid chromatography. Methanolic carotenoid solutions were exposed to whole tobacco smoke from 1-5 unfiltered cigarettes. The carotenoid concentrations after exposure to each cigarette were determined from their optical densities. Results: Carotenoids were generally stable at 37o C. In methanol and THF only lycopene was significantly depleted (15%) after 4h exposure. Lutein and zeaxanthin in methanol and DCM heated to 80o C resisted thermal degradation, and were decreased by 10%, compared to lycopene and ß-carotene, which were 70% degraded. Levels of lutein and zeaxanthin extracted from heated plasma were 50% higher than those of ß-carotene and lycopene. Lutein and zeaxanthin resisted tobacco-smoke induced autoxidation compared to lycopene and ß-carotene, which were respectively 25 and 15% degraded Conclusions: The macular pigments, lutein and zeaxanthin, were more resistant to heat and tobacco-smoke induced oxidative stress than lycopene and ß-carotene. Previous experiments also showed the resistance of the macular pigment to autoxidation in response to hypochlorite and photoirradiation and supports a role for these carotenoids as a stable shield to protect the retina from oxidative insult and resulting injury.
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