Humulone
Encyclopedia
Humulone is a bitter-tasting chemical compound
found in the resin of mature hops
(Humulus lupulus
). Humulone is a prevalent member of the class of compounds known as alpha acid
s, which collectively give beer its characteristic bitter flavor.
derivative
with three isoprenoid side-chains. Two side-chains are prenyl groups and one is an isovaleryl group.
. These “alpha acids” survive the boiling process, although numerous oxidized derivatives are produced. The iso-alpha acids are significantly more soluble than humulone at the pH levels typically present in the brewing process.
C6H2(OH)4 + (CH3)2CHCH2COCl → C6H(OH)4COCH2CH(CH3)2
C6H(OH)4COCH2CH(CH3)2 + 2 CH2BrC4H7 → C21H30O5
isovaleryl-CoA + 3 malonyl-CoA 4 CoASH + 3 CO2 + 3-methyl-1-(2,4,6-trihydroxyphenyl)butan-1-one
3-methyl-1-(2,4,6-trihydroxyphenyl)butan-1-one + 2 DMAPP →C21H30O5
including anti-bacterial, antioxidant, and cyclooxygenase-2 inhibitory activities.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
found in the resin of mature hops
Hops
Hops are the female flower clusters , of a hop species, Humulus lupulus. They are used primarily as a flavoring and stability agent in beer, to which they impart a bitter, tangy flavor, though hops are also used for various purposes in other beverages and herbal medicine...
(Humulus lupulus
Humulus lupulus
Humulus lupulus is a species of Humulus in the Cannabaceae family.Common hop is a dioecious, perennial herbaceous climbing plant which sends up new shoots in early spring and dies back to the cold-hardy rhizome in autumn...
). Humulone is a prevalent member of the class of compounds known as alpha acid
Alpha acid
Alpha acids are a class of compounds primarily of importance to the production of beer. They are found in the resin glands of the flowers of the hop plant and are the source of hop bitterness. Alpha acids may be isomerized to form iso-alpha acids by the application of heat in solution...
s, which collectively give beer its characteristic bitter flavor.
Chemistry
In terms of structure, humulone is a phloroglucinolPhloroglucinol
Phloroglucinol is a benzenetriol. It is an organic compound that is used in the synthesis of pharmaceuticals and explosives. This molecule exists in two forms, or tautomers, 1,3,5-trihydroxybenzene, which has phenol-like, and 1,3,5-cyclohexanetrione , which has ketone-like character. These two...
derivative
Derivative (chemistry)
In chemistry, a derivative is a compound that is derived from a similar compound by some chemical or physical process. In the past it was also used to mean a compound that can be imagined to arise from another compound, if one atom is replaced with another atom or group of atoms, but modern...
with three isoprenoid side-chains. Two side-chains are prenyl groups and one is an isovaleryl group.
Isohumulone
During the brewing process, humulone degrades to cis- and trans-isohumuloneIsohumulone
Isohumulones are compounds that contribute to the bitter taste of beer. They are in the class of compounds known as iso-alpha acids. The bitterness of beer is measured according to the International Bitterness Units scale, with one IBU corresponding to 1 part per million of isohumulone...
. These “alpha acids” survive the boiling process, although numerous oxidized derivatives are produced. The iso-alpha acids are significantly more soluble than humulone at the pH levels typically present in the brewing process.
Synthesis
Humulone can be synthesized by the acylation of 1,2,3,5-benzenetetrol with isovaleryl chloride followed to give 2,3,4,6-tetrahydroxyisovalerophenone. This step is followed by prenylation with 1-bromo-3-methyl-2-butene to give humulone.C6H2(OH)4 + (CH3)2CHCH2COCl → C6H(OH)4COCH2CH(CH3)2
C6H(OH)4COCH2CH(CH3)2 + 2 CH2BrC4H7 → C21H30O5
Biosynthesis
The biosynthesis of humulone in Humulus lupulus starts with an isovaleryl-CoA unit and 3 malonyl-CoA units catalyzed by phlorovalerophenone synthase. This conversion yields the benzenoid 3-methyl-1-(2,4,6-trihydroxyphenyl)butan-1-one. Dimethylallyl pyrophospate is then obtained from the deoxyxylulose pathway, where prenylation of the benzenoid occurs, yielding humulone.isovaleryl-CoA + 3 malonyl-CoA 4 CoASH + 3 CO2 + 3-methyl-1-(2,4,6-trihydroxyphenyl)butan-1-one
3-methyl-1-(2,4,6-trihydroxyphenyl)butan-1-one + 2 DMAPP →C21H30O5
Biological properties
Studies of humulone have determined that it possesses a variety of biological activities in vitroIn vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
including anti-bacterial, antioxidant, and cyclooxygenase-2 inhibitory activities.