Humulus lupulus is a perennialherbaceous plant up to 10 metres (33 feet) tall, living up to 20 years.[5] It has simpleleaves with 3–5 deep lobes that can be opposite or alternate.[6] The species is triggered by the longer summer days to flower,[7] usually around July or August in the Northern Hemisphere.[8] The plant isdioecious, with male and female flowers on separate plants. The fragrant flowers arewind-pollinated.[9] The staminate (male) flowers do not have petals, while the pistillate (female) flowers have petals enveloping the fruit. The female flower cones (orstrobili) are known ashops.[5] The fruit is anachene, meaning that it is dry and does not split open at maturity.[6] The achene is surrounded by tepals and lupulin-secreting glands are concentrated on the fruit.[10][11]
The species is sometimes described as abine rather than a vine because it has stiff downward facing hairs that provide stability and allow it to climb.[5]
Hops are unique for containingsecondary metabolites,flavonoids,oils, andpolyphenols that impact the flavor of the products they are common in, such asbeer.[13] The bitter flavors in hops can be accounted for by acids composed ofprenylatedpolyketides (a group of secondary metabolites), which highly impact the taste of hop-based products.[14] Multiple genes have been identified as factors in the expression of taste includingO-methyltransferase 1, geranyl diphosphatesynthase, andchalcone synthase.Genomic analyses have shown evidence that the intervention of humans in the selection process of the hop over the thousands of years it has been cultivated have provided noticeable enhancements in aroma and bitterness as well as selection of varieties with high yield rates.[15]
Humulus lupulus, in Kent, England. Taken in late August, showing light-green cones.
Predicted genes inhomologous primary contigs have been identified as accounting for various traitsexpressed via variation in the growth, flowering, and stress responses in the plant. These homologous primary contigs correspond to regions with large amounts ofsequence variation.Genes in the hop that contain higher rates ofsequence divergence in homologous primary contigs (overlappingDNA sequences inherited by a common ancestor) have been attributed to the expression of flowering, growth and responses to (bothabiotic andbiotic) stress in the plant. The responses to stress are thought to manifest in the distinct differences and difficulties in the cultivation processes between geographically popular varieties of the hop plant.[16] Outside environmental stress, such as changes in temperature and water availability has also been shown to significantly alter thetranscriptome and incite reductions in genes known to be involved in the synthesis ofsecondary metabolites (including bitter acids), which areorganic compounds produced that do not impact development or reproduction of hops. Environmental stress has also been shown to reduceexpression of thevalerophenonesynthasegene, which is known to be an essential genetic component in the regulation of bitter acid production. This shows that impacts of outside stress onH. lupulus likely has a direct implication of the expression of the bitter flavor that remains an essential component of the popularity of the plant.[13]
Humulus lupulus extract is antimicrobial, an activity which has been exploited in the manufacture of natural deodorant.[19]
SpentH. lupulus extract has also been shown to haveantimicrobial and anti-biofilm activities, raising the possibility this waste product of the brewing industry could be developed for medical applications.[20]
Extracts of the bitter alpha-acids present inH. lupulus have been shown to decrease nocturnal activity, acting as a sleep aide, in certain concentrations.[21]
Because of the growing understanding regarding the hop's overlap in gene structures withcannabidiolic acid synthase, the precursor structure tocannabidiol, there is a gap in general understanding about potential unknown compounds and benefits in hops. As the understanding of the health benefits available in cannabidiol increases, there is a growing demand to further investigate the overlap between cannabidiolic acid synthase andH. lupulus.[22]
Thegenome ofH. lupulus is relatively large and has been shown to be a similar size to thehuman genome. The complexity of the hop genome has made it difficult to understand and identify unknown genetic properties, however with the growing availability of accessiblesequencing, there is room for more advanced understanding of the plant.[22] Because of the growing concern ofclimate change, and the assumption that there will be an increase ofheat waves, it is likely that growing large yields of hops could become more difficult. This could result in changes to thetranscriptome of the hop, or result in a decrease of certain varieties, leaving less room for further research.[13]
The hop is within the same family of plants such ashemp andmarijuana, calledCannabaceae.[16] The hop plant diverged fromCannabis sativa over 20 million years ago and has evolved to be three times the physical size.[23][24][15][25] The hop andC. sativa are estimated to have approximately a 73% overlap in genomic content.[26] The overlap betweenenzymes includespolyketide synthases andprenyltransferases.[27] The hop andC. sativa also have significant overlap in thecannabidiolic acid synthase gene, which is expressed in the tissues of the leaves in both plants.[16]
The genus nameHumulus is a medieval name that was at some point Latinized after being borrowed from a Germanic source exhibiting theh•m•l consonant cluster, as in Middle Low Germanhomele.
According to Soviet IranistVasily Abaev this could be a word ofSarmatian origin which is present in the modern Ossetian language (Ossetian:Хуымæллæг) and derives from proto-Iranianhauma-arayka, anAryanhaoma.[33]
From Sarmatian dialects this word spread across Eurasia, thus creating a group of related words in Turkic, Finno-Ugric, Slavic and Germanic languages (seeRussian:хмель,Chuvashхăмла,Finnishhumala,Hungariankomló,Mordovianкомла,Avarхомеллег).
The specific epithetlupulus is Latin for "small wolf".[34] The name refers to the plant's tendency to strangle other plants, mainlyosiers or basket willows (Salix viminalis), like a wolf does a sheep.[5] Hops could be seen growing over these willows so often that it was named the willow-wolf.[34]
The English wordhop is derived from theMiddle Dutch wordhoppe, also meaningHumulus lupulus.[35]
H. lupulus is first mentioned in 768 CE whenKing Pepin donated hops to a monastery in Paris. Cultivation was first recorded in 859 CE, in documents from a monastery inFreising, Germany.[36]
The chemical compounds found inH. lupulus are the main components in flavoring and bittering beer. The fragrant flower cones, known as hops, impart a bitter flavor and also have aromatic and preservative qualities.[37] Some other compounds help with creating foam in beer. Chemicals such aslinalool andaldehydes contribute to the flavor of beer. The main components of bitterness in beer areiso-alpha acids, with many other compounds contributing to beer's overall bitterness.[38] Until the Middle Ages, many varieties of plant were used to flavor beer, including most commonlyMyrica gale.[36]H. lupulus became favored because it contains preserving agents which prolong the viability of a brew.
^Burnham, Robyn J. (2014)."Vitis riparia".CLIMBERS: Censusing Lianas in Mesic Biomes of Eastern Regions. University of Michigan College of Literature, Sciences and the Arts. Retrieved2017-04-02.
^ab"Humulus lupulus".NewCROP, the New Crop Resource Online Program. Retrieved2017-04-02.
^Zanoli, Paola; Zavatti, Manuela (2008). "Pharmacognostic and pharmacological profile of Humulus lupulus L".Journal of Ethnopharmacology.116 (3):383–396.doi:10.1016/j.jep.2008.01.011.PMID18308492.
^abNatsume, S.; Takagi, H.; Shiraishi, A.; Murata, J.; Toyonaga, H.; Patzak, J.; Takagi, M.; Yaegashi, H.; Uemura, A.; Mitsuoka, C.; Yoshida, K. (2014-11-20). "The Draft Genome of Hop (Humulus lupulus), an Essence for Brewing".Plant and Cell Physiology.56 (3):428–441.doi:10.1093/pcp/pcu169.ISSN0032-0781.PMID25416290.
^Benkherouf, Ali Y.; Soini, Sanna L.; Stompor, Monika; Uusi-Oukari, Mikko (February 2019). "Positive allosteric modulation of native and recombinant GABAA receptors by hops prenylflavonoids".European Journal of Pharmacology.852:34–41.doi:10.1016/j.ejphar.2019.02.034.ISSN0014-2999.PMID30797788.S2CID73456325.
^Franco, L.; Sánchez, C.; Bravo, R.; Rodriguez, A.; Barriga, C.; Juánez, Javier Cubero (2012-06-01). "The sedative effects of hops (Humulus lupulus), a component of beer, on the activity/rest rhythm".Acta Physiologica Hungarica.99 (2):133–139.doi:10.1556/APhysiol.99.2012.2.6.ISSN0231-424X.PMID22849837.
^Langezaal CR, Chandra A, Scheffer JJ (1992). "Antimicrobial screening of essential oils and extracts of some Humulus lupulus L. cultivars".Pharm Weekbl Sci.14 (6):353–356.doi:10.1007/bf01970171.PMID1475174.S2CID12561634.
"Czech hop varieties". Žatec: Chmelařský institut, 2012.on-line
Barchet, Ron. "German hops in craft brewing". Wolnzach: Hopfen-Rundschau, 2014.
Biendl, Martin. "Hops and health". Wolnzach: German Hop Museum, 2013.
Hieronymus, Stan. "For the love of hops: The practical guide to aroma, bitterness and the culture of hops". Boulder, CO: Brewers Publications, a division of the Brewers Association, 2012.
Melnychuk, M. D.; Boyko, A. L.; Hryhoryuk, I. P.; Likhanov, A. F.; Klyuvadenko, A. A.; Martyn, H. H.; Kukovenko, V. I. "Hop (Humulus lupulus L.): From cell to plant". Kyiv: Printeko, 2013.
Nesvadba, Vladimír. "Development and tradition of Czech hop varietes". Žatec: Hop Research Institute, 2013.
Neve, Ray A. "Hops". London: Chapman and Hall, 1991.
Skomra, Urszula. "Polish hop cultivars". Puławy: Institute of Soil Science and Plant Cultivation, 2010.
-2017-Ystad.jpg)
