How Do Xanthophylls Protect Lipid Membranes from Oxidative Damage?

Here, we address the problem of the antioxidant activityof carotenoidsin biomembranes. The activity of lutein and zeaxanthin in the quenchingof singlet oxygen generated by photosensitization was monitored inlipid vesicles using a singlet oxygen-sensitive fluorescent probeand with the application of fluorescence lifetime imaging microscopy.The antioxidant activity of xanthophylls was interpreted on the basisof electron paramagnetic resonance oximetry results showing that xanthophyllsconstitute a barrier to the penetration of molecular oxygen into lipidmembranes: to a greater extent in the 13-cis configurationthan in all-trans. These results are discussed inrelation to the trans-cis photoisomerization of xanthophylls observed in the human retina.It can be concluded that photoisomerization of xanthophylls is a regulatorymechanism that is important for both the modulation of light filtrationthrough the macula and photoprotection by quenching singlet oxygenand creating a barrier to oxygen permeation to membranes.

Automated summary

In this study, the antioxidant activity of carotenoids in biomembranes was investigated. The quenching activity of lutein and zeaxanthin in singlet oxygen generation was measured in lipid vesicles using a fluorescent probe and fluorescence lifetime imaging microscopy. The results showed that xanthophylls act as a barrier to the penetration of molecular oxygen into lipid membranes, especially in the 13-cis configuration. This photoisomerization of xanthophylls is a regulatory mechanism important for light filtration and photoprotection.