What is the Difference Between Carotene and Xanthophyll

The main difference between carotene and xanthophyll is that carotene gives an orange color whereas xanthophyll gives a yellow color. Furthermore, carotene is a hydrocarbon that does not contain an oxygen atom in its structure while xanthophyll is a hydrocarbon that contains an oxygen atom in its structure.

Carotene and xanthophyll are the two classes of carotenoids, which are tetraterpene plant pigments, serving as accessory pigments in photosynthesis. They are responsible for giving red-orange to yellow color, especially to fruits and vegetables.

Key Areas Covered

1. What is Carotene
     – Definition, Structure, Function
2. What is Xanthophyll
     – Definition, Structure, Function
3. What are the Similarities Between Carotene and Xanthophyll
     – Outline of Common Features
4. What is the Difference Between Carotene and Xanthophyll
     – Comparison of Key Differences

Key Terms

Accessory Pigments, Carotene, Carotenoids, Xanthophyll

What is Carotene

Carotene is one of the two types of carotenoids present in plants responsible for the orange color of the plant. Generally, carotenoids are organic pigment only produced by photosynthetic organisms including plants, algae, and bacteria. The main function of carotenoids is to serve as accessory pigments in photosynthesis. Although animals cannot synthesize carotenoids inside their body, these compounds play a key role as antioxidants and anti-inflammatory molecules.

Figure 1: Orange Color in Carrots

Furthermore, the main structural feature of carotenes used to distinguish them from xanthophyll is the absence of any oxygen atoms in the molecule. Also, there are four main types of carotenes as β-carotene, α-carotene, and lycopene. Mainly, β-carotene and, to a certain extent, α-carotene are responsible for the synthesis of vitamin A inside the animal body. Looking at the sources, β-carotene occurs in cantaloupe, mangoes, papaya, carrots, sweet potatoes, spinach, kale, and pumpkin while α-carotene occurs in pumpkin, carrots, tomatoes, collards, tangerines, winter squash, and peas. Whereas, lycopene occurs in watermelons, tomatoes, guavas, and grapefruit.

What is Xanthophyll

Xanthophyll is the second type of carotenoids found in plants, giving a yellow color to the plant. However, the structure of xanthophyll contains a single oxygen atom in contrast to carotene. However, same as carotene, xanthophyll occurs in leaves of plants in high quantities. In addition, animal bodies contain xanthophyll, which is plant-based. As examples, the egg yolk, fat tissue, and the skin contain xanthophyll derived from plants. Primarily, lutein is the form of xanthophylls found in the egg yolk of chickens. 

Figure 2: Examples of Carotenoids

Also, two types of xanthophylls known as lutein and zeaxanthin occur in the macula lutea or the yellow spot in the retina of the human eye. They are responsible for the central vision of the eye. Moreover, they protect the eye from the blue light. Therefore, kale, spinach, turnip greens, summer squash, pumpkin, paprika, yellow-fleshed fruits, avocado, and egg yolk are good sources of lutein and zeaxanthin. In general, these two xanthophylls are effective in age-related macular degeneration (AMD), which leads to blindness. Furthermore, lutein is known to prevent the atherosclerosis formation due to its antioxidant effect on cholesterol, which in turn prevents the building up of cholesterol in arteries.

Similarities Between Carotene and Xanthophyll

• Carotene and xanthophyll are the two classes of carotenoids.
• They are tetraterpenes-related unsaturated hydrocarbon substances having the same formula C₄₀H_x.
• Also, both give a red-orange to yellow color to parts of plants.
• And, both of them occur in the chloroplasts.
• Animals are unable to produce them.
• Furthermore, they serve as accessory pigments in photosynthesis, capturing the sunlight and passing onto chlorophyll a.
• However, the wavelengths absorbed by them are different from the wavelengths absorbed by chlorophylls. Also, they absorb light in the UV range.
• Moreover, these pigments serve as antioxidants, deactivating free radicals.
• They have anti-inflammatory effects; hence, they perform an immune function in the body.
• Additionally, both types of carotenoids are known to reduce the risk of cardiovascular disease and cancer.

Difference Between Carotene and Xanthophyll

Definition

Carotene refers to an orange or red plant pigment, including beta-carotene found in carrots and many other plant structures while xanthophyll refers to a yellow or brown carotenoid plant pigment which causes the autumn colors of leaves. Thus, this is the main difference between carotene and xanthophyll. 

Absorption Wavelength

Βeta-carotene, which is a carotene, absorbs 450 nm wavelength, while lutein and vioxanthan, which are xanthophylls, absorb 435 nm. Hence, this is another difference between carotene and xanthophyll.

Color

Also, the color produced by each is another  difference between carotene and xanthophyll. While carotene gives an orange color, xanthophyll gives a yellow color.

Oxygen Atoms

Moreover, one other difference between carotene and xanthophyll is the presence of oxygen atoms in their structure. Carotene does not contain an oxygen atom in its structure while xanthophyll contains an oxygen atom in its structure.

Occurrence

Carotene mainly occurs in cantaloupe, mangoes, papaya, carrots, sweet potatoes, spinach, kale, and pumpkin while xanthophyll occurs in kale, spinach, turnip greens, summer squash, pumpkin, paprika, yellow-fleshed fruits, avocado, and egg yolk. This is also a difference between carotene and xanthophyll.

Conclusion

Carotene is one of the two types of carotenoids that mainly occur in plant parts including fruits and vegetables. It is responsible for giving an orange color to the plant. Additionally, it does not contain any oxygen atoms in its structure. In contrast, xanthophyll is the other type of carotenoid responsible for giving a yellow color to the plant. Significantly, it contains a single oxygen atom in its structure. Both carotene and xanthophyll serve as accessory pigments which capture and pass sunlight to chlorophyll a. However, the main difference between carotene and xanthophyll is the color they give to the plant.

References:

1. Szalay, Jessie. “What Are Carotenoids?” LiveScience, Purch, 15 Oct. 2015, Available Here.

Image Courtesy:

1. “carrots-lying-carrot-yellow-beet-2667337” By anaterate (Pixabay License) via Pixabay
2. “Beta-carotene-2D-skeletal” (Public Domain) via Commons Wikimedia  
3. “Zeaxanthin” (Public Domain) via Commons Wikimedia