What is "carotene"

hydrocarbon found in carrots and other plants, 1861, from German carotin, coined 1831 by German chemist H.W.F. Wackenroder (1789-1854) from Latin carota "carrot" (see carrot) + German form of chemical suffix -ine (2), denoting a hydrocarbon.

n. 1 (context organic chemistry English) A class of tetraterpene plant pigments; they vary in colour from yellow, through orange to red, this colour originating in a chain of alternating single bond and double bonds. 2 (context organic chemistry English) Specifically, a number of isomers of tetraterpene hydrocarbons, C₄₀H₅₆, (especially ''beta-carotene''), present in carrots etc, which are converted into vitamin A in the liver.

1. n. an orange isomer of an unsaturated hydrocarbon found in many plants; is converted into vitamin A in the liver [syn: provitamin A, carotin]

2. yellow or orange-red fat-soluble pigments in plants

The term carotene (also carotin, from the Latin carota, "carrot") is used for many related unsaturated hydrocarbon substances having the formula CH, which are synthesized by plants but in general cannot be made by animals (with the sole known exception of some aphids and spider mites which acquired the synthetic genes from fungi). Carotenes are photosynthetic pigments important for photosynthesis. Carotenes contain no oxygen atoms. They absorb ultraviolet, violet, and blue light and scatter orange or red light, and (in low concentrations) yellow light.

Carotenes are responsible for the orange colour of the carrot, for which this class of chemicals is named, and for the colours of many other fruits, vegetables and fungi (for example, sweet potatoes, chanterelle and orange cantaloupe melon). Carotenes are also responsible for the orange (but not all of the yellow) colours in dry foliage. They also (in lower concentrations) impart the yellow coloration to milk-fat and butter. Omnivorous animal species which are relatively poor converters of coloured dietary carotenoids to colourless retinoids have yellowed-coloured body fat, as a result of the carotenoid retention from the vegetable portion of their diet. The typical yellow-coloured fat of humans and chickens is a result of fat storage of carotenes from their diets.

Carotenes contribute to photosynthesis by transmitting the light energy they absorb to chlorophyll. They also protect plant tissues by helping to absorb the energy from singlet oxygen, an excited form of the oxygen molecule O which is formed during photosynthesis.

β-Carotene is composed of two retinyl groups, and is broken down in the mucosa of the human small intestine by β-carotene 15,15'-monooxygenase to retinal, a form of vitamin A. β-Carotene can be stored in the liver and body fat and converted to retinal as needed, thus making it a form of vitamin A for humans and some other mammals. The carotenes α-carotene and γ-carotene, due to their single retinyl group (β- ionone ring), also have some vitamin A activity (though less than β-carotene), as does the xanthophyll carotenoid β- cryptoxanthin. All other carotenoids, including lycopene, have no beta-ring and thus no vitamin A activity (although they may have antioxidant activity and thus biological activity in other ways).

Animal species differ greatly in their ability to convert retinyl (beta- ionone) containing carotenoids to retinals. Carnivores in general are poor converters of dietary ionone-containing carotenoids. Pure carnivores such as ferrets lack β-carotene 15,15'-monooxygenase and cannot convert any carotenoids to retinals at all (resulting in carotenes not being a form of vitamin A for this species); while cats can convert a trace of β-carotene to retinol, although the amount is totally insufficient for meeting their daily retinol needs.

Carotene (foaled 1983 in Ontario) is a Canadian Thoroughbred Hall of Fame racehorse who holds the filly or mare record for winning the most Sovereign Awards. Bred by David Willmot's Kinghaven Farms, she was a daughter of the British sire Great Nephew, who also sired Epsom Derby winners Grundy and Shergar. Carotene's dam was Carrot Top, a mare David Willmot purchased in foal from the Whitney family at the 1982 dispersal sale of their bloodstock in the United Kingdom.