Anthocyanidins regenerating xanthophylls: a quantum mechanical approach to eye health

The xanthophylls lutein and zeaxanthin accumulate in human retina and protect vision functions against blue light, singlet oxygen and triplet photosensitizers, but are easily degraded by free radicals involved in lipid oxidation in eye tissue. Polyphenols may regenerate xanthophylls from their initial oxidation products, the carotenoid radical cations, by electron transfer protecting the 'yellow spot.' The reorganization energy of the donor/acceptor transition state should equal reaction free energy for optimal diffusion-controlled regeneration of the xanthophylls by polyphenols according to Marcus theory for electron transfer. Anthocyanidins match the reduction potential of xanthophyll radicals in contrast to the more reducing catechins and tocopherols, which overshoot energetically. Quantum mechanics may provide the explanation for the protective effect of blueberry on vision.