{{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<ref name="ReferenceA">{{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}}</ref> | 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= | Density= | MeltingPt= | BoilingPt= | Solubility= }} |Section3={{Chembox Hazards | MainHazards= | FlashPt= | AutoignitionPt = }} }}
'''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.<ref>{{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}}</ref>
=== Formation === Isohumulones are generated by the isomerization of humulone.<ref name="ReferenceA"/><ref>{{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}}</ref><ref>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}}</ref> thumb|left|400px|Isomerization of humulone to ''cis''- and ''trans''-isohumulone{{Clearleft}}
==See also== *Beer chemistry
== References == {{reflist}}
Category:Bitter compounds Category:Cyclopentenes Category:3-Hydroxypropenals Category:Humulus