Vitamin A2
{{DISPLAYTITLE:Vitamin A2}}
{{Chembox
| Name = Vitamin A2 alcohol
| ImageFile = Vitamin A2.svg
| ImageSize = 200px
| IUPACName = 3,4-Didehydroretinol
| PIN = (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
| OtherNames = Retinol 2; 3,4-Dehydroretinol
|Section1={{Chembox Identifiers
| PubChem=6436043
| ChemSpiderID = 4940721
| CASNo = 79-80-1
| EC_number = 201-226-4
| UNII = 104621892X
| ChEMBL = 1797132
| ChEBI = 132246
| KEGG = C21797
| StdInChI=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+
| StdInChIKey = XWCYDHJOKKGVHC-OVSJKPMPSA-N
| SMILES = CC1=C(C(CC=C1)(C)C)/C=C/C(=C/C=C/C(=C/CO)/C)/C
}}
|Section2={{Chembox Properties
|C=20|H=28|O=1
}}
}}
Vitamin A2 is a subcategory of vitamin A.{{cite journal |vauthors=Babino D, Golczak M, Kiser PD, Wyss A, Placzewski K, von Lintig J |title=The Biochemical Basis of Vitamin A3 Production in Arthropod Vision |journal= ACS Chem Biol |volume= 11 |issue= 4 |pages=1049–1057 |year= 2016| pmid= 26811964 |doi=10.1021/acschembio.5b00967|pmc= 4841470 }}
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.
Human skin naturally contains the alcohol form.{{cite journal |vauthors=Törmä H, Vahlquist A |title=Biosynthesis of 3-dehydroretinol (vitamin A2) from all-trans-retinol (vitamin A1) in human epidermis |journal= J Invest Dermatol |volume= 85 |issue= 6 |pages=498–500 |year= 1985| pmid= 4067325 |doi=10.1111/1523-1747.ep12277290|doi-access= free }}{{cite journal |vauthors=Vahlquist A |title=The identification of dehydroretinol (vitamin A2) in human skin |journal= Experientia |volume= 36 |issue= 3 |pages=317–318 |year= 1980 |pmid=7371787 |doi=10.1007/bf01952299|s2cid=31357743 }} In humans, CYP27C1 converts ordinary A1 (all-trans retinoids) to A2. The enzyme also converts 11-cis-retinal.{{cite journal |last1=Kramlinger |first1=VM |last2=Nagy |first2=LD |last3=Fujiwara |first3=R |last4=Johnson |first4=KM |last5=Phan |first5=TT |last6=Xiao |first6=Y |last7=Enright |first7=JM |last8=Toomey |first8=MB |last9=Corbo |first9=JC |last10=Guengerich |first10=FP |title=Human cytochrome P450 27C1 catalyzes 3,4-desaturation of retinoids. |journal=FEBS Letters |date=May 2016 |volume=590 |issue=9 |pages=1304–12 |doi=10.1002/1873-3468.12167 |pmid=27059013|pmc=4864060 |doi-access=free }}
Vitamin A2 was first identified by Richard Alan Morton using newly-developed absorption spectroscopy in 1941.{{cite journal |last1=Goodwin |first1=T W |title=R. A. Morton |journal=Nature |date=1977 |volume=266 |issue=5600 |page=394 |doi=10.1038/266394a0 |bibcode=1977Natur.266..394G |s2cid=31211784 |doi-access=free }}