Xanthophyll

Xanthophylls are a class of carotenoids that contain oxygen, making them more polar than purely hydrocarbon carotene molecules. They occur widely in plants, algae, and some bacteria, contributing yellow to orange hues to leaves and fruits. Unlike carotenes, which are purely hydrocarbon, xanthophylls feature oxygen-containing functional groups such as hydroxyl, carbonyl, or epoxide groups. Common examples include lutein and zeaxanthin, the dihydroxy carotenoids that accumulate in the human retina, as well as violaxanthin, neoxanthin, and astaxanthin.

Biological roles include participation in light harvesting and photoprotection during photosynthesis. They help dissipate excess absorbed light energy as heat through the xanthophyll cycle, which interconverts violaxanthin, antheraxanthin, and zeaxanthin to prevent photooxidative damage and support non-photochemical quenching.

Human health and diet: Lutein and zeaxanthin accumulate in the macula of the eye and are studied for potential protective effects against age-related macular degeneration. They are obtained from leafy greens, corn, eggs, and certain fruits, with intestinal absorption facilitated by dietary fats.

Industrial and regulatory aspects: Xanthophylls are used as natural colorants in foods and feeds. Marigold extracts provide lutein; astaxanthin is used to color farmed salmon and other seafood, and is available as a supplement. Regulatory status varies by compound and country, but xanthophylls are generally recognized as safe when used as directed in foods and feeds.

Biochemistry and biosynthesis: In plants, xanthophylls arise from carotenoid biosynthesis with oxygenation steps catalyzed by specific enzymes, yielding polycyclic pigments that are lipophilic but more polar than carotenes due to their oxygen-containing groups.