Humulus lupulus

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

Hops are unique for containing secondary metabolites, flavonoids, oils, and polyphenols that impact the flavor of the products they are common in, such as beer.[10] The bitter flavors in hops can be accounted for by acids composed of prenylated polyketides (a group of secondary metabolites), which highly impact the taste of hop-based products.[11] Multiple genes have been identified as factors in the expression of taste including O-methyltransferase 1, geranyl diphosphate synthase, and chalcone 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.[12]

Predicted genes in homologous primary contigs have been identified as accounting for various traits expressed via variation in the growth, flowering, and stress responses in the plant. These homologous primary contigs correspond to regions with large amounts of sequence variation. Genes in the hop that contain higher rates of sequence divergence in homologous primary contigs (overlapping DNA sequences inherited by a common ancestor) have been attributed to the expression of flowering, growth and responses to (both abiotic and biotic) 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.[13] Outside environmental stress, such as changes in temperature and water availability has also been shown to significantly alter the transcriptome and incite reductions in genes known to be involved in the synthesis of secondary metabolites (including bitter acids), which are organic compounds produced that do not impact development or reproduction of hops. Environmental stress has also been shown to reduce expression of the valerophenone synthase gene, which is known to be an essential genetic component in the regulation of bitter acid production. This shows that impacts of outside stress on H. lupulus likely has a direct implication of the expression of the bitter flavor that remains an essential component of the popularity of the plant.[10]

• Humulus lupulus contains xanthohumol, which is converted by large intestine bacteria into the phytoestrogen 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]

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]

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]

Cultivation of hops in Ystad 2017

'Golden' hop

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]

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 V. Abaev this could be a word of Sarmatian origin which is present in the modern Ossetian language (Ossetian: Хуымæллæг) and derives from proto-Iranian hauma-arayka, an Aryan haoma.[30]

From Sarmatian dialects this word spread across Eurasia, thus creating a group of related words in Turkic, Finno-Ugric, Slavic and Germanic languages (see Russian: хмель, Chuvash хăмла, Finnish humala, Hungarian komló, Mordovian комла, Avar хомеллег).

The specific epithet lupulus is Latin for "small wolf".[31] The name refers to the plant's tendency to strangle other plants, mainly osiers or basket willows (Salix viminalis), like a wolf does a sheep.[3] Hops could be seen growing over these willows so often that it was named the willow-wolf.[31]

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

• 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)

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

• "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.