Vitamin A₂

Vitamin A₂ alcohol
Names
	IUPAC name 3,4-Didehydroretinol
	Preferred IUPAC name (2E,4E,6E,8E)-3,7-Dimethyl-9-(2,6,6-trimethylcyclohexa-1,3-dien-1-yl)nona-2,4,6,8-tetraen-1-ol
	Other names Retinol 2; 3,4-Dehydroretinol
Identifiers
CAS Number	79-80-1;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:132246;
ChEMBL	ChEMBL1797132;
ChemSpider	4940721;
ECHA InfoCard	100.001.116
EC Number	201-226-4;
KEGG	C21797;
PubChem CID	6436043;
UNII	104621892X;
CompTox Dashboard (EPA)	DTXSID401018959 ;
	InChI InChI=1S/C20H28O/c1-16(8-6-9-17(2)13-15-21)11-12-19-18(3)10-7-14-20(19,4)5/h6-13,21H,14-15H2,1-5H3/b9-6+,12-11+,16-8+,17-13+ Key: XWCYDHJOKKGVHC-OVSJKPMPSA-N;
	SMILES CC1=C(C(CC=C1)(C)C)/C=C/C(=C/C=C/C(=C/CO)/C)/C;
Properties
Chemical formula	C20H28O
Molar mass	284.443 g·mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Vitamin A₂ is a subcategory of vitamin A.^[1]

As with all vitamin A forms, A₂ can exist as an aldehyde, Dehydroretinal (3,4-dehydroretinal), an alcohol, 3,4-dehydroretinol (vitamin A₂ alcohol) or an acid, 3,4-dehydroretinoic acid (vitamin A₂ acid). Many cold-blooded vertebrates use the aldehyde for their visual system to obtain a red-shifted sensitive spectrum.^[2]

Human skin naturally contains the alcohol form.^[3]^[4] In humans, CYP27C1 converts ordinary A₁ (all-trans retinoids) to A₂. The enzyme also converts 11-cis-retinal.^[2]

Vitamin A₂ was first identified by Richard Alan Morton using newly-developed absorption spectroscopy in 1941.^[5]

References

^ Babino D, Golczak M, Kiser PD, Wyss A, Placzewski K, von Lintig J (2016). "The Biochemical Basis of Vitamin A3 Production in Arthropod Vision". ACS Chem Biol. 11 (4): 1049–1057. doi:10.1021/acschembio.5b00967. PMC 4841470. PMID 26811964.
^ ^a ^b Kramlinger, VM; Nagy, LD; Fujiwara, R; Johnson, KM; Phan, TT; Xiao, Y; Enright, JM; Toomey, MB; Corbo, JC; Guengerich, FP (May 2016). "Human cytochrome P450 27C1 catalyzes 3,4-desaturation of retinoids". FEBS Letters. 590 (9): 1304–12. doi:10.1002/1873-3468.12167. PMC 4864060. PMID 27059013.
^ Törmä H, Vahlquist A (1985). "Biosynthesis of 3-dehydroretinol (vitamin A2) from all-trans-retinol (vitamin A1) in human epidermis". J Invest Dermatol. 85 (6): 498–500. doi:10.1111/1523-1747.ep12277290. PMID 4067325.
^ Vahlquist A (1980). "The identification of dehydroretinol (vitamin A2) in human skin". Experientia. 36 (3): 317–318. doi:10.1007/bf01952299. PMID 7371787. S2CID 31357743.
^ Goodwin, T W (1977). "R. A. Morton". Nature. 266 (5600): 394. Bibcode:1977Natur.266..394G. doi:10.1038/266394a0. S2CID 31211784.

[Babino_et_al._2016-1] Babino D, Golczak M, Kiser PD, Wyss A, Placzewski K, von Lintig J (2016). "The Biochemical Basis of Vitamin A3 Production in Arthropod Vision". ACS Chem Biol. 11 (4): 1049–1057. doi:10.1021/acschembio.5b00967. PMC 4841470. PMID 26811964.

[27c1-2] Kramlinger, VM; Nagy, LD; Fujiwara, R; Johnson, KM; Phan, TT; Xiao, Y; Enright, JM; Toomey, MB; Corbo, JC; Guengerich, FP (May 2016). "Human cytochrome P450 27C1 catalyzes 3,4-desaturation of retinoids". FEBS Letters. 590 (9): 1304–12. doi:10.1002/1873-3468.12167. PMC 4864060. PMID 27059013.

[Törmä_H_and_Vahlquist_A,_1985-3] Törmä H, Vahlquist A (1985). "Biosynthesis of 3-dehydroretinol (vitamin A2) from all-trans-retinol (vitamin A1) in human epidermis". J Invest Dermatol. 85 (6): 498–500. doi:10.1111/1523-1747.ep12277290. PMID 4067325.

[Vahlquist_A,_1980-4] Vahlquist A (1980). "The identification of dehydroretinol (vitamin A2) in human skin". Experientia. 36 (3): 317–318. doi:10.1007/bf01952299. PMID 7371787. S2CID 31357743.

[Goodwin_1977-5] Goodwin, T W (1977). "R. A. Morton". Nature. 266 (5600): 394. Bibcode:1977Natur.266..394G. doi:10.1038/266394a0. S2CID 31211784.

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