View source for Humulus

{{Short description|Genus of flowering plants belonging to the hemp and hackberry family}}
{{distinguish|hamulus}}
{{Automatic taxobox
|image = humulus.jpg
|image_caption = Common hop plant (''[[Humulus lupulus]]'')
|taxon = Humulus
|authority = [[Carl Linnaeus|L.]]
|subdivision_ranks=Species
|subdivision=[[#Species|See text]].
|synonyms_ref =<ref name = "30027247-2" />
|synonyms =
*''Lupulus'' Mill.
*''Waldensia'' Lavy
}}

'''''Humulus''''', or '''hop''', is a small [[genus]] of [[flowering plant]]s in the [[family (biology)|family]] [[Cannabaceae]]. The hop is [[native plant|native]] to [[temperateness|temperate]] regions of the Northern Hemisphere. [[Hops]] are the female flowers (seed cones, strobiles) of the hop [[species]] ''[[Humulus lupulus|H. lupulus]]''; as a main flavor and aroma ingredient in many [[beer]] styles, ''H. lupulus'' is widely cultivated for use by the brewing industry.

==Description==
Although frequently referred to in American literature as the hops "vine", it is technically a [[bine (botany)|bine]]; unlike [[vine]]s, which use [[tendril]]s, suckers, and other appendages for attaching themselves, bines have stout stems with stiff hairs to aid in climbing. In British literature the term "vine" is generally reserved for the grape genus ''[[Vitis]]''. ''Humulus'' is described as a twining [[perennial plant|perennial]] [[herbaceous plant]] which sends up new shoots in early spring and dies back to the cold-hardy [[rhizome]] in autumn. Hop shoots grow very rapidly, and at the peak of growth can grow {{convert|20|to|50|cm|abbr=off|in|sigfig=1}} per week. Hop bines climb by wrapping clockwise (except for ''[[Humulus japonicus]]'') around anything within reach, and individual bines typically grow between {{convert|2|and|15|m|abbr=off|ft|sigfig=1}} depending on what is available to grow on. The [[leaves]] are opposite, with a {{convert|7|to|12|cm|in|abbr=on|frac=4}} leafstalk and a heart-shaped, fan-lobed blade {{convert|12|to|25|cm|in|abbr=on|frac=4}} long and broad; the edges are coarsely toothed. When the hop bines run out of material to climb, horizontal shoots sprout between the leaves of the main stem to form a network of stems wound round each other.<ref name=RHSAZ>{{cite book | editor-last = Brickell | editor-first = Christopher | title = The Royal Horticultural Society A-Z Encyclopedia of Garden Plants | year = 2008 | page = 550 | publisher = Dorling Kindersley | location = United Kingdom | isbn = 9781405332965}}</ref>

Male and female flowers of the hop plant are [[dioecious]], developing on separate plants. Female plants, which produce the hop flowers used in brewing beer, are often propagated [[vegetative reproduction|vegetatively]] and grown in the absence of male plants. This prevents pollination and the development of viable [[seed]]s, which are sometimes considered undesirable for brewing beer owing to the potential for off-flavors arising from the introduction of fatty acids from the seeds.<ref>[http://www.agroatlas.ru/cultural/Humulus_lupulus_K_en.htm Interactive Agricultural Ecological Atlas of Russia and Neighboring Countries. Economic Plants and their Diseases, Pests and Weeds. ''Humulus lupulus''.] {{webarchive|url=https://web.archive.org/web/20120310182625/http://www.agroatlas.ru/cultural/Humulus_lupulus_K_en.htm |date=2012-03-10 }}</ref>

The characteristic bitterness imparted by the addition of hops to the brewing process is mainly due to the presence of bitter acids, which are prenylated acylphloroglucinol derivatives.<ref>{{cite book |last1=Verzele |first1=M. |title=Chemistry and analysis of hop and beer bitter acids |last2=De Keukeleire |first2=D. |publisher=Elsevier |year=1991 |isbn=978-0-444-88165-6 |location=New York}}</ref> Bitter acids are divided into the alpha-acids, with humulone the major compound, and the beta-acids, with [[lupulone]] the major compound;<ref name="Almaguer et al 2014" /> the alpha-acids isomerize during the brewing process to form iso-alpha acids, which themselves have a bitter taste.<ref>{{cite journal |last1=Jaskula |first1=Barbara |last2=Kafarski |first2=Pawel |last3=Aerts |first3=Guido |last4=De Cooman |first4=Luc |date=August 2008 |title=A Kinetic Study on the Isomerization of Hop α-Acids |journal=Journal of Agricultural and Food Chemistry |volume=56 |issue=15 |pages=6408–6415 |doi=10.1021/jf8004965 |pmid=18598038}}</ref><ref name="Almaguer et al 2014" /> These hop acids are [[vinylogy|vinylogous acids]], with acidic ring enols in conjugation with ring and substituent carbonyl groups.<ref>{{cite journal |last1=Urban |first1=Jan |last2=Dahlberg |first2=Clinton J. |last3=Carroll |first3=Brian J. |last4=Kaminsky |first4=Werner |date=28 January 2013 |title=Absolute Configuration of Beer′s Bitter Compounds |journal=Angewandte Chemie International Edition |volume=52 |issue=5 |pages=1553–1555 |doi=10.1002/anie.201208450 |pmc=3563212 |pmid=23239507}}</ref><ref>{{cite journal |last1=De Keukeleire |first1=Denis |date=February 2000 |title=Fundamentals of beer and hop chemistry |journal=Química Nova |volume=23 |issue=1 |pages=108–112 |doi=10.1590/S0100-40422000000100019 |doi-access=free}}</ref> Plants in the genus ''Humulus'' produce [[terpenophenolic]] metabolites.<ref>{{cite book |last1=Page |first1=Jonathan E. |title=Recent Advances in Phytochemistry |last2=Nagel |first2=Jana |year=2006 |isbn=9780080451251 |volume=40 |pages=179–210 |chapter=Biosynthesis of terpenophenolic metabolites in hop and cannabis |doi=10.1016/S0079-9920(06)80042-0}}</ref> Hops also contain [[xanthohumol]], a [[prenylated]] [[chalcone]], and other compounds.<ref name=":0">{{cite journal |last1=Stevens |first1=Jan F |last2=Page |first2=Jonathan E |date=May 2004 |title=Xanthohumol and related prenylflavonoids from hops and beer: to your good health! |journal=Phytochemistry |volume=65 |issue=10 |pages=1317–1330 |doi=10.1016/j.phytochem.2004.04.025 |pmid=15231405|bibcode=2004PChem..65.1317S }}</ref>

==Taxonomy==
[[File:환삼덩굴 잎.JPG|thumb|''[[Humulus japonicus]]'' leaves]]
{{As of|2020|10}}, the following species were accepted:<ref name = "30027247-2" >{{cite web |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30027247-2 |title=''Humulus'' L. |author=<!--Not stated--> |date=2017 |website=Plants of the World Online |publisher=Board of Trustees of the Royal Botanic Gardens, Kew |access-date=14 October 2020 }}</ref>
{{div col|colwidth=24em}}
*''[[Humulus americanus]]'' <small>Nutt.</small>
*''[[Humulus cordifolius]]'' <small>Miq.</small>
*''[[Humulus lupulus]]'' <small>L.</small>
*''[[Humulus neomexicanus]]'' <small>(A.Nelson & Cockerell) Rydb.</small>
*''[[Humulus pubescens]]'' <small>(E.Small) Tembrock</small>
*''[[Humulus scandens]]'' <small>(Lour.) Merr.</small> (syn. ''[[Humulus japonicus]] <small>Siebold & Zucc.</small>)
*''[[Humulus yunnanensis]]'' <small>Hu</small>
{{div col end}}
For brewers' hops, which are specific cultivars, and propagated by [[asexual reproduction]], see the article, "[[List of hop varieties]]".

==Uses==
Hops are boiled with the [[wort]] in [[brewing]] beer and sometimes added post-ferment; they impart a bitterness, flavor, as well as aroma to the finished product.<ref name="Almaguer et al 2014">{{cite journal |last1=Almaguer |first1=Cynthia |last2=Schönberger |first2=Christina |last3=Gastl |first3=Martina |last4=Arendt |first4=Elke K. |last5=Becker |first5=Thomas |title=Humulus lupulus - a story that begs to be told. A review: Humulus lupulus - a story that begs to be told |journal=Journal of the Institute of Brewing |date=September 2014 |doi=10.1002/jib.160 |doi-access=free }}</ref>

In [[pharmacy]] ''lupulus'' is the designation of hop. The dried [[catkin]]s, commonly referred to as hop cones, of the female plant of ''H. lupulus'' are used to prepare [[infusion]] of hop, [[tincture]] of hop, and [[extract]] of hop.<ref name="colliers">{{Cite Collier's|wstitle=Hop}}</ref>

Some of the compounds hops contain are under preliminary research for their potential health properties.<ref name=":0" />

==References==
{{Reflist}}

==External links==
* [https://www.ars.usda.gov/pacific-west-area/corvallis-or/national-clonal-germplasm-repository/docs/ncgr-corvallis-humulus-germplasm/ Jeanine S. DeNoma: ''Humulus Genetic Resources'' (USDA ARS National Clonal Germplasm Repository)]
* [https://www.uvm.edu/~pass/perry/hops.html Hops varieties research]
* [https://pfaf.org/User/plant.aspx?LatinName=Humulus+lupulus Plants for a Future: ''Humulus lupulus'']

{{Taxonbar|from=Q158790}}
{{Authority control}}

[[Category:Humulus| ]]
[[Category:Medicinal plants]]
[[Category:Stem vegetables]]
[[Category:Dioecious plants]]
[[Category:Rosales genera]]
[[Category:Taxa named by Carl Linnaeus]]