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Generic term for a class of carotenes and their oxygenated derivatives (xanthophylls) consisting of 8 isoprenoid units (thus, tetraterpenes) joined so that the orientation of these units is reversed at the center, placing the two central methyl groups in a 1,6 relationship in contrast to the 1,5 of the others. All carotenoids may be formally derived from the acyclic C40H56 structure known as lycopene, with its long central chain of conjugated double bonds by hydrogenation, dehydrogenation, oxidation, cyclization, or combinations of these. Included as carotenoids are some compounds arising from certain rearrangements or degradations of the carbon skeleton, but not retinol and related C20 compounds. The nine-carbon end groups may be acyclic with 1,2 and 5,6 double bonds or cyclohexanes with a single double bond at 5,6 or 5,4 or cyclopentanes or aryl groups; these are now designated by Greek letter prefixes preceding "carotene" (α and δ, which are used in the trivial names α-carotene and δ-carotene, are not used for that reason). Suffixes (for example, -oic acid, -oate, -al, -one, -ol) indicate certain oxygen-containing groups (for example, acid, ester, aldehyde, ketone, alcohol); all other substitutions appear as prefixes (for example, alkoxy-, epoxy-, hydro-). ). The configuration about all double bonds is trans unless cis and locant numbers appear. The prefix retro- is used to indicate a shift of one position of all single and double bonds; apo- indicates shortening of the molecule. Many carotenoids have anticancer activities.
Farlex Partner Medical Dictionary © Farlex 2012
Generic term for a class of carotenes and their oxygenated derivatives (xanthophylls).
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
carotenoidsA large group of yellow or orange pigments occurring in plants some of which have antioxidant properties. Some of the carotenoids are carotenes.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
carotenoidsa group of yellow/orange pigments found in plants, animals and microorganisms, which includes CAROTENES (orange) and xanthophylls (yellow).
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
Carotenoids are yellow to deep-red pigments.
Mentioned in: Vitamin A Deficiency
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.