Carotene
Carotene (also known as carotin), derived from the Latin carota (referring to the carrot),[1][2] encompasses a group of unsaturated hydrocarbon substances characterized by the formula C40Hx. These compounds, which exhibit vibrant hues perceptible to the human eye, play a crucial role in the photosynthetic processes of plants. Interestingly, while plants can synthesize these compounds, animals cannot.
Molecular Structure[edit | edit source]
Chemically, carotenes are polyunsaturated hydrocarbons made up of 40 carbon atoms, a varying number of hydrogen atoms, and no other elements. They may be terminated by hydrocarbon rings at one or both ends. All carotenes display colors to the human eye, a result of their extensive systems of conjugated double bonds. In essence, carotenes are tetraterpenes, derived biochemically from four 10-carbon terpene units, which are themselves formed from eight 5-carbon isoprene units.[3]
These carotenoids are found in two primary forms: alpha-carotene (α-carotene) and beta-carotene (β-carotene). Other variants such as gamma-, delta-, epsilon-, and zeta-carotene (γ, δ, ε, and ζ-carotene) also exist. Notably, since they're hydrocarbons and devoid of oxygen, carotenes are fat-soluble and insoluble in water. This distinguishes them from other carotenoids like xanthophylls, which do contain oxygen.
Dietary Sources[edit | edit source]
A variety of foods are rich in carotenes.[4] They include:
Sweet potatoes[5] Carrots[6][7] Wolfberries or goji[8] Cantaloupe melon[9] Mangoes[10] Apricots[11] Persimmon[12] ... [shortened for brevity] Notably, the absorption of carotenes from these foods is enhanced when consumed with fats due to their fat-solubility. Cooking these foods until their cell walls break and release their color also facilitates better absorption. Each 6 μg of dietary β-carotene provides an equivalent of 1 μg of retinol, or 1 RE (Retinol Equivalent). This is tantamount to 3⅓ IU of vitamin A.
Role in Photosynthesis[edit | edit source]
Carotenes contribute indispensably to photosynthesis by transmitting the light energy they capture to chlorophyll. They also play a protective role in plant tissues, absorbing energy from singlet oxygen – a high-energy form of the O2 molecule – that emerges during photosynthesis.
Carotene and Vitamin A[edit | edit source]
β-Carotene stands out as it is made up of two retinyl groups. In the human small intestine's mucosa, it is cleaved by β-carotene 15,15'-monooxygenase to produce retinal, a form of vitamin A. Given that β-Carotene can be stored in body fat and the liver, and later be converted to retinal as required, it functions as a form of vitamin A for humans and certain mammals. Other carotenes, including α-carotene and γ-carotene, possess some vitamin A activity due to their single retinyl group (β-ionone ring). However, not all carotenoids confer vitamin A activity. For instance, lycopene doesn't have any β-ring, thus lacking vitamin A activity, though it may possess antioxidant capabilities.
Variability Among Animal Species[edit | edit source]
Animal species exhibit significant variations in their ability to convert retinyl (beta-ionone) containing carotenoids to retinals. While carnivores are generally inefficient converters of dietary ionone-containing carotenoids, pure carnivores like ferrets entirely lack the β-carotene 15,15'-monooxygenase enzyme, making them unable to convert any carotenoids to retinals. In contrast, cats can convert a minuscule amount of β-carotene to retinol, but this is woefully inadequate for their daily retinol requirements.[13]
See also[edit | edit source]
Carotene Resources | ||
---|---|---|
|
|
Translate to: East Asian
中文,
日本,
한국어,
South Asian
हिन्दी,
Urdu,
বাংলা,
తెలుగు,
தமிழ்,
ಕನ್ನಡ,
Southeast Asian
Indonesian,
Vietnamese,
Thai,
မြန်မာဘာသာ,
European
español,
Deutsch,
français,
русский,
português do Brasil,
Italian,
polski
Navigation: Wellness - Encyclopedia - Health topics - Disease Index - Drugs - World Directory - Gray's Anatomy - Keto diet - Recipes
Search WikiMD
Ad.Tired of being Overweight? Try W8MD's physician weight loss program.
Semaglutide (Ozempic / Wegovy and Tirzepatide (Mounjaro) available.
Advertise on WikiMD
WikiMD is not a substitute for professional medical advice. See full disclaimer.
Credits:Most images are courtesy of Wikimedia commons, and templates Wikipedia, licensed under CC BY SA or similar.
Contributors: Prab R. Tumpati, MD