Editing Xanthophyll (section)

==Example compounds==
The group of xanthophylls includes (among many other compounds) [[lutein]], [[zeaxanthin]], [[neoxanthin]], [[violaxanthin]], [[flavoxanthin]], and α- and β-[[cryptoxanthin]]. The latter compound is the only known xanthophyll to contain a beta-ionone ring, and thus β-[[cryptoxanthin]] is the only xanthophyll that is known to possess pro-vitamin A activity for mammals. Even then, it is a vitamin only for plant-eating mammals that possess the enzyme to make retinal from carotenoids that contain beta-ionone (some carnivores lack this enzyme). In species other than mammals, certain xanthophylls may be converted to hydroxylated retinal-analogues that function directly in vision. For example, with the exception of certain flies, most insects use the xanthophyll derived R-isomer of 3-hydroxyretinal for visual activities, which means that β-[[cryptoxanthin]] and other xanthophylls (such as lutein and zeaxanthin) may function as forms of visual "vitamin A" for them, while carotenes (such as beta carotene) do not.