Humulus lupulus

Common hop
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Rosales
Family:	Cannabaceae
Genus:	Humulus
Species:	H. lupulus
Binomial name
Humulus lupulus L.
Synonyms[1]
Humulus cordifolius Miq. Humulus volubilis Salisb. nom. illeg. Humulus vulgaris Gilib. Lupulus amarus Gilib. Lupulus communis Gaertn. Lupulus humulus Mill. Lupulus scandens Lam. nom. illeg.

Humulus lupulus, the common hop or hops, is a

As the female cone-shaped flowers (

H. lupulus contains myrcene, humulene, xanthohumol, myrcenol, linalool, tannins, and resin.

• Humulus lupulus contains xanthohumol, which is converted by large intestine bacteria into the
  8-prenylnaringenin, which may have a relative binding affinity to estrogen receptors^[14] as well as potentiating effects on GABA_A receptor activity^[15]
• Humulus lupulus extract is antimicrobial, an activity which has been exploited in the manufacture of natural deodorant.[16]
• Spent H. lupulus extract has also been shown to have antimicrobial and anti-biofilm activities, raising the possibility this waste product of the brewing industry could be developed for medical applications.^[17]
• Extracts of the bitter alpha-acids present in H. lupulus have been shown to decrease nocturnal activity, acting as a sleep aide, in certain concentrations.^[18]

Because of the growing understanding regarding the hop's overlap in gene structures with cannabidiolic acid synthase, the precursor structure to cannabidiol, 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 and H. lupulus.^[19]

Limitations

The genome of H. lupulus is relatively large and has been shown to be a similar size to the human genome. The complexity of the hop genome has made it difficult to understand and identify unknown genetic properties, however with the growing availability of accessible sequencing, there is room for more advanced understanding of the plant.^[19] Because of the growing concern of climate change, and the assumption that there will be an increase of heat waves, it is likely that growing large yields of hops could become more difficult. This could result in changes to the transcriptome of the hop, or result in a decrease of certain varieties, leaving less room for further research.^[10]

Taxonomy

Relation to Cannabis sativa

The hop is within the same family of plants such as hemp and marijuana, called Cannabaceae.^[13] The hop plant diverged from Cannabis sativa over 20 million years ago and has evolved to be three times the physical size.^{[20][21][12][22]} The hop and C. sativa are estimated to have approximately a 73% overlap in genomic content.^[23] The overlap between enzymes includes polyketide synthases and prenyltransferases.^[24] The hop and C. sativa also have significant overlap in the cannabidiolic acid synthase gene, which is expressed in the tissues of the leaves in both plants.^[13]

Varieties

The five varieties of this species (Humulus lupulus) are:

• H. l. var. lupulus – Europe, western Asia
• H. l. var. cordifolius – eastern Asia
• H. l. var. lupuloides (syn. H. americanus) – eastern North America
• H. l. var. neomexicanus – western North American.^[25]
• H. l. var. pubescens – midwestern and eastern North America^[26][27]

Many cultivars are found in the list of hop varieties. A yellow-leafed ornamental cultivar, Humulus lupulus 'Aureus', is cultivated for garden use. It is also known as golden hop, and holds the Royal Horticultural Society's Award of Garden Merit (AGM).^[28][29]

Etymology

The genus name Humulus is a medieval name that was at some point Latinized after being borrowed from a Germanic source exhibiting the h•m•l consonant cluster, as in Middle Low German homele.

According to Soviet Iranist

The English word hop is derived from the Middle Dutch word hoppe, also meaning Humulus lupulus.^[32]

Distribution and habitat

The plant is native to Europe, western Asia and North America.^[31]

It grows best in the latitude range of 38°–51° in full sun with moderate amounts of rainfall.^[2]

Ecology

The flowers attract

• Damson hop aphid (Phorodon humuli)
• Two spotted spider mite (Tetranychus urticae)
• Japanese beetle (
  Popillia japonica
  )
• Comma butterfly (Polygonia c-album)
• Pale tussock moth (Calliteara pudibunda)
• Currant pug moth (Eupithecia assimilata)
• Buttoned snout moth (Hypena rostralis)
• Buff ermine moth (Spilosoma lutea)

Diseases

• Downy mildew (Pseudoperonospora humuli)
• Powdery mildew (Podosphaera macularis)

Toxicity

H. lupulus can cause dermatitis to some who handle them. It is estimated that about 1 in 30 people are affected by this.^[9]

Uses

H. lupulus is first mentioned in 768 CE when King Pepin donated hops to a monastery in Paris. Cultivation was first recorded in 859 CE, in documents from a monastery in Freising, Germany.^[33]

The chemical compounds found in H. 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.^[34] Some other compounds help with creating foam in beer. Chemicals such as linalool and aldehydes contribute to the flavor of beer. The main components of bitterness in beer are iso-alpha acids, with many other compounds contributing to beer's overall bitterness.^[35] Until the Middle Ages, many varieties of plant were used to flavor beer, including most commonly Myrica gale.^[33] H. lupulus became favored because it contains preserving agents which prolong the viability of a brew.

Culture

H. lupulus was voted the county flower of Kent in 2002 following a poll by the wild flora conservation charity Plantlife.^[36]

References

Bibliography

• "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.
• Kopp, Sylvia. "Barley & hops: The craft beer book". Berlin: Gestalten, 2014.
• 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.

External links

Wikimedia Commons has media related to Humulus lupulus.

• Purdue University article
• Botanical.com - a wealth of information on the Hop plant and its past and modern uses
• Armeniapedia.org - Medicinal uses of hops in Armenia
• 2005-10-25 Oregon State University Anti-cancer Compound in Beer Gaining Interest