Xanthophyll

Xanthophylls are yellow colors found all around nature. They are part of a group of compounds called carotenoids, which also includes carotenes. The name xanthophyll comes from Greek words meaning "yellow" and "leaf," because these pigments create a yellow band when scientists study leaf colors.

These pigments help give many leaves and flowers their bright yellow colors. They also protect plants from too much sunlight. Xanthophylls are found in many foods we eat, like corn, peas, and eggs, which makes these foods yellow.

Xanthophylls are interesting to scientists because they were one of the first plant pigments studied using a method called chromatography. This helped researchers learn more about how plants make and use colors.

Molecular structure

Xanthophylls and carotenes are both types of carotenoids, which means they have similar structures. Xanthophylls contain oxygen atoms, but carotenes are made only of hydrocarbons and have no oxygen. This makes xanthophylls more polar than carotenes. Xanthophylls can have oxygen as hydroxyl groups or as oxygen atoms forming epoxides.

Occurrence

Xanthophylls are found in the leaves of green plants. They help manage light energy and protect chlorophyll when there is too much light.

Animals, including humans, get xanthophylls from the plants they eat. The yellow color in chicken egg yolks comes from xanthophylls in their food, mainly lutein.

In our eyes, the yellow spot called the macula lutea gets its color from lutein and zeaxanthin, which we get from eating certain foods. These help protect our eyes by blocking blue and ultraviolet light. They do not help us see directly, but they play a role in how we sense certain kinds of light.

Example compounds

Xanthophylls include important compounds such as lutein, zeaxanthin, neoxanthin, violaxanthin, flavoxanthin, and α- and β-cryptoxanthin. Among these, β-cryptoxanthin is special because it has a beta-ionone ring and can act like a vitamin for some animals that eat plants. This only works for animals that have a certain enzyme. In some insects, certain xanthophylls might help with vision.

Xanthophyll cycle

The xanthophyll cycle is a way that plants protect themselves from too much sunlight. It changes yellow pigments, called xanthophylls, from one form to another.

When there is too much light, plants change a pigment called violaxanthin into another pigment called zeaxanthin. This helps the plant keep its energy safe and protect its leaves. Tiny water organisms, like diatoms and dinoflagellates, also use this cycle to shield themselves from bright light.

Food sources

Xanthophylls are found in young leaves and special leaves called etiolated leaves. They are also in many foods such as papaya, peaches, prunes, and squash. Some vegetables like kale have these pigments. Spinach has some, as do parsley, peas, squash, and pistachios.