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Retinal

All-trans-retinal
Skeletal formula of retinal
Ball-and-stick model of the retinal molecule
Names
IUPAC name
(2E,4E,6E,8E)-3,7-Dimethyl-9-(2,6,6-trimethylcyclohexen-1-yl)nona-2,4,6,8-tetraenal
Other names
retinene; retinaldehyde; vitamin A aldehyde; RAL
Identifiers
116-31-4 YesY
3D model (Jmol) Interactive image
ECHA InfoCard 100.003.760
PubChem 1070
UNII RR725D715M YesY
Properties
C20H28O
Molar mass 284.44 g·mol−1
Appearance Orange crystals from petroleum ether
Melting point 61 to 64 °C (142 to 147 °F; 334 to 337 K)
Nearly insoluble
Solubility in fat Soluble
Related compounds
Related compounds
retinol; retinoic acid; beta-carotene; dehydroretinal; 3-hydroxyretinal; 4-hydroxyretinal
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY  (what is YesYN ?)
Infobox references

Retinal is also known as retinaldehyde. It was originally called retinene, and renamed after it was discovered to be vitamin A aldehyde. Retinal is one of the many forms of vitamin A (the number of which varies from species to species). Retinal is a polyene chromophore, bound to proteins called opsins, and is the chemical basis of animal vision. Retinal allows certain microorganisms to convert light into metabolic energy.

Vertebrate animals ingest retinal directly from meat, or they produce retinal from carotenoids, either from one of two carotenes (α-carotene, β-carotene) or from β-cryptoxanthin, a type of xanthophyll. These carotenoids must be obtained from plants or other photosynthetic organisms. No other carotenoids can be converted by animals to retinal, and some carnivores cannot convert any carotenoids at all. The other main forms of vitamin A, retinol, and a partially active form, retinoic acid, may both be produced from retinal.

Invertebrates such as insects and squid use hydroxylated forms of retinal in their visual systems, which derive from conversion from other xanthophylls.

Living organisms produce retinal (RAL) by irreversible oxidative cleavage of carotenoids. For example,

catalyzed by a beta-carotene 15,15'-monooxygenase or a beta-carotene 15,15'-dioxygenase. Just as carotenoids are the precursors of retinal, retinal is the precursor of the other forms of vitamin A. Retinal is interconvertible with retinol (ROL), the transport and storage form of vitamin A

catalyzed by retinol dehydrogenases (RDHs) and alcohol dehydrogenases (ADHs). Retinol is called vitamin A alcohol, or more often, simply vitamin A. Retinal can also be oxidized to retinoic acid (RA)


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