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β-Carotene (beta-carotene) is an organic, strongly colored red-orange pigment abundant in fungi, [7] plants, and fruits. It is a member of the carotenes , which are terpenoids (isoprenoids), synthesized biochemically from eight isoprene units and thus having 40 carbons .
α-Carotene is produced when the all-trans lycopene first undergoes reaction with epsilon-LCY then a second reaction with beta-LCY; whereas β-carotene is produced by two reactions with beta-LCY. α- and β-Carotene are the most common carotenoids in the plant photosystems but they can still be further converted into xanthophylls by using beta ...
Also downregulated is the enzyme beta-carotene 15,15'-dioxygenase (formerly known as beta-carotene 15,15'-monooxygenase) coded for by the BCMO1 gene, responsible for symmetrically cleaving β-carotene into retinal. [8] Absorbed β-carotene is either incorporated as such into chylomicrons or first converted to retinal and then retinol, bound to ...
Distribution of macular pigment constituent carotenoids presented in scale onto a photograph of a healthy human retina. Meso-zeaxanthin, lutein, and 3R,3′R-zeaxanthin are the main carotenoids in the macula lutea, found in a ratio of 1:1:1, and are collectively referred to as macular pigment (MP). [3]
The two primary isomers of carotene, α-carotene and β-carotene, differ in the position of a double bond (and thus a hydrogen) in the cyclic group at one end (the right end in the diagram at right). β-Carotene is the more common form and can be found in yellow, orange, and green leafy fruits and vegetables.
Overconsumption of beta-carotene can only cause carotenosis, a harmless and reversible cosmetic condition in which the skin turns orange. Preformed vitamin A absorption and storage in the liver occur very efficiently until a pathologic condition develops. [21] When ingested, 70–90% of preformed vitamin A is absorbed and used. [21]
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[2] [3] They generally have biological activity in the plant host and play a role in plant growth or defense against competitors, pathogens, or predators. [ 2 ] Phytochemicals are generally regarded as research compounds rather than essential nutrients because proof of their possible health effects has not been established yet.