Isohumulone
{{chembox
| Watchedfields = changed
| verifiedrevid = 435318755
| ImageFile=Isohumulone v2.svg
| ImageSize=200px
| IUPACName=3,4-Dihydroxy-5-(3-methylbut- 2-enyl)-2-(3-methyl-1-oxobutyl)-4-(4- methyl-1-oxopent-3-enyl)-1- cyclopent-2-enone{{cite journal | year = 2013 | last1 = Urban | first1 = Jan | last2 = Dahlberg | first2 = Clinton | last3 = Carroll | first3 = Brian | last4 = Kaminsky | first4 = Werner | title = Absolute Configuration of Beer′s Bitter Compounds | volume = 52 | issue = 5 | pages = 1553–1555 | doi = 10.1002/anie.201208450 | journal = Angew. Chem. Int. Ed.| pmc = 3563212 | pmid=23239507}}
| OtherNames=
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 84039
| InChI = 1/C21H30O5/c1-12(2)7-9-15-19(24)18(16(22)11-14(5)6)20(25)21(15,26)17(23)10-8-13(3)4/h7-8,14-15,25-26H,9-11H2,1-6H3
| InChIKey = QARXXMMQVDCYGZ-UHFFFAOYAV
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C21H30O5/c1-12(2)7-9-15-19(24)18(16(22)11-14(5)6)20(25)21(15,26)17(23)10-8-13(3)4/h7-8,14-15,25-26H,9-11H2,1-6H3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = QARXXMMQVDCYGZ-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|??}}
| CASNo=25522-96-7
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = E2S413495Y
| PubChem=93090
| SMILES = O=C(C1(O)C(/O)=C(\C(=O)C1C/C=C(/C)C)C(=O)CC(C)C)C\C=C(/C)C
}}
|Section2={{Chembox Properties
| C=21 | H=30 | O=5
| Appearance=
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|Section3={{Chembox Hazards
| MainHazards=
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Isohumulones are chemical compounds that contribute to the bitter taste of beer and are in the class of compounds known as iso-alpha acids. They are found in hops.
Beer
The bitterness of beer is measured according to the International Bitterness Units scale, with one IBU corresponding to one part-per-million of isohumulone. When beer is exposed to light, these compounds can decompose in a reaction catalyzed by riboflavin to generate free-radical species by the homolytic cleavage of the exocyclic carbon-carbon bond. The cleaved acyl side-chain radical then decomposes further, expelling carbon monoxide and generating 1,1-dimethylallyl radical. This radical can finally react with sulfur-containing amino acids, such as cysteine, to create 3-methylbut-2-ene-1-thiol, a thiol which causes beer to develop a "skunky" flavor.{{cite web|url=http://www.eurekalert.org/pub_releases/2001-10/uonc-ucf101701.php| title=UNC chemists figure out what causes 'skunky beer'|publisher=eurekalert.org}}
= Formation =
Isohumulones are generated by the isomerization of humulone.{{Cite journal | doi = 10.1016/j.tifs.2005.11.012 | title = A better control of beer properties by predicting acidity of hop iso-α-acids | year = 2006 | last1 = Blanco | first1 = Carlos A. | last2 = Rojas | first2 = Antonio | last3 = Caballero | first3 = Pedro A. | last4 = Ronda | first4 = Felicidad | last5 = Gomez | first5 = Manuel | last6 = Caballero | first6 = Isabel | journal = Trends in Food Science & Technology | volume = 17 | issue = 7 | pages = 373}}Esslinger, H. M. and Narziss, L. 2003. “Beer.” in Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co. KGaA, 2009 {{doi|10.1002/14356007.a03_421}}
File:S-Humulone Isomerization.svg{{Clearleft}}
