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Humulus lupulus L. (Cannabaceae), commonly named hop, is widely grown around the world for its use in the brewing industry. Its female inflorescences (hops) are particularly prized by brewers because they produce some secondary metabolites that confer bitterness, aromas and antiseptic properties to the beer. These sought-after metabolites include terpenes and sesquiterpenes, found in essential oil, but also prenylated phenolic compounds, mainly acylphloroglucinols (bitter acids) from the series of α -acids (humulone derivatives). These metabolites have shown numerous biological activities, including among others, antimicrobial, sedative and estrogenic properties. This review provides an inventory of hop’s chemistry, with an emphasis on the secondary metabolites and their biological activities. These compounds of biological interest are essentially produced in female inflorescences, while other parts of the plant only synthetize low quantities of them. Lastly, our article provides an overview of the research in plant biotechnology that could bring alternatives for hops metabolites production.

Xanthohumol (XH) is an important prenylated flavonoid that is found within the inflorescence of Humulus lupulus L. (Hop plant). XH is an important ingredient in beer and is considered a significant bioactive agent due to its diverse medicinal applications, which include anti-inflammatory, antimicrobial, antioxidant, immunomodulatory, antiviral, antifungal, antigenotoxic, antiangiogenic, and antimalarial effects as well as strong anticancer activity towards various types of cancer cells. XH acts as a wide ranging chemopreventive and anticancer agent, and its isomer, 8-prenylnaringenin, is a phytoestrogen with strong estrogenic activity. The present review focuses on the bioactivity of XH on various types of cancers and its pharmacokinetics. In this paper, we first highlight, in brief, the history and use of hops and then the chemistry and structure–activity relationship of XH. Lastly, we focus on its prominent effects and mechanisms of action on various cancers and its possible use in cancer prevention and treatment. Considering the limited number of available reviews on this subject, our goal is to provide a complete and detailed understanding of the anticancer effects of XH against different cancers.

Studies on the improvement of hops (Humulus lupulus) in Brazil are recent and seek to establish self-sufficiency in production. Knowledge of the variability of genotypes available in the country is of fundamental importance for the development of a hop improvement program. The objective of the research was to characterize and identify hop parents with agronomic and brewing potential for the Planalto Catarinense region, Brazil. The randomized block design arranged in a 3x4 factorial scheme was used with 12 treatments: (Factor 1: three years of cultivation (2019, 2020 and 2021) and combined with factor: four genotypes (Cascade, Chinook, Columbus and Hallertau). The characters evaluated were fresh mass of plants (MFP, g), green mass of cones (MTV, g), dry mass of cones (MSC, g), alpha-acid content (ALFA, %) and production (PROD, g per plant). The Hallertauer genotype showed better performance and differentiated behavior for the characters of fresh mass of plants, dry mass of cones and production, when compared to the others. Thus, from these results it was observed that there is variation available for the genetic improvement of hops for these characters, a factor that will allow obtaining productive gains in the development of new cultivars, based on this promising genotype. RESUMO: Os estudos visando o melhoramento de lúpulo (Humulus lupulus) no Brasil são recentes e buscam estabelecer a autossuficiência da produção. O conhecimento da variabilidade dos genótipos disponíveis no país é de fundamental importância para o desenvolvimento de um programa de melhoramento de lúpulo. O objetivo do trabalho foi identificar genitores de lúpulo com potencial agronômico e cervejeiro para o Planalto Catarinense, Brasil. Foi utilizado o delineamento em blocos casualizados em esquema fatorial 3x4 com 12 tratamentos: Fator 1: três anos de cultivo (2019, 2020 e 2021) e combinado com o fator 2: quatro genótipos (Cascade, Chinook, Columbus e Hallertau). Os caracteres avaliados foram a massa fresca de plantas (MFP, g), massa verde de cones (MTV, g), a massa seca de cones (MSC, g), os teores de alfa-ácidos (ALFA, %) e a produção (PROD, g per planta). O genótipo Hallertauer demonstrou melhor desempenho e comportamento diferenciado para os caracteres de massa fresca de plantas, massa seca de cones e produção, quando comparado aos demais. Assim, a partir destes resultados observou-se que, existe variação disponível ao melhoramento genético do lúpulo para esses caracteres, fator que permitirá obter ganhos produtivos no desenvolvimento de novas cultivares, a partir deste genótipo promissor.

Bioactive compounds extracted from plant are of great value for those enterprises interested in the use of natural products; plant tissue culture techniques guarantee a reliable and constant biomass production. Hop (Humulus lupulus L.), with its wealth in bioactive compounds, may represent an invaluable resource. The present study focused on the characterization of vitro-derived leaves and roots of two hop plant types, Cascade and Gianni. Extracts obtained from the selected hop explants were investigated, determining their polyphenolic content as their antioxidant capacity, applying DPPH, ABTS and FRAP assays; moreover, extract molecular profile was obtained through UHPLC-MS/MS. Results confirm the wealthy in bioactive compounds and the antioxidant properties of the tested vitro-derived hop explants. The qualitative characterization of vitro-derived hop tissue extracts evidenced the presence of twenty one different compounds, already identified in open field grown hop plants, such as polyphenols, α- and β-acids, as well as xanthohumol and isoxanthohumol. The obtained outcomes lay the groundwork to further investigate the potential of vitro-derived hop plantlets as bioactive compounds source.Key messageCharacterizing and recovering secondary metabolites from micropropagated hop plantlets.

Hop ( Humulus lupulus L.) is a dioecious climbing plant that is emblematic for the brewing industry because of its specialized metabolites. Many studies have focused on hop metabolism without considering the microbiota associated with hop tissues, although over the past decade, a paradigm shift has redefined plants as holobionts, with complex associations between the plant host and its associated microbial communities. In this study, we investigated the effects of three wild hop genotypes cultivated in two different agricultural soils under controlled conditions on specialized metabolite production and on bacterial community composition across different hop compartments (rhizosphere soil, roots, and leaves). Phytochemical analysis of leaf contents revealed distinct metabolic profiles across the six ‘genotype×soil’ interactions, driven by variations in the biosynthesis of prenylated chalcones, α- and β-type bitter acids, and their derivatives. PERMANOVA results demonstrated that both ‘genotype’ and ‘soil’ factors significantly influenced leaf metabolite composition, each explaining approximately 28% of the observed variance. However, the strongest effect was observed for the ‘genotype×soil’ interaction, which accounted for 66% of the variance. In parallel, soil type, hop genotype, and their interaction significantly shape hop-associated bacterial communities, with a predominant interaction effect in each compartment (rhizosphere soil, roots and leaves) (R² = 0.74, 0.74 and 0.32, respectively). Furthermore, Spearman microbiome–metabolome correlation analysis revealed that bacterial families were positively correlated with the biosynthesis of key metabolites, particularly bitter acids. Our findings further suggest that the hop-associated microbiota may contribute to metabolic biosynthesis, opening new perspectives for optimizing metabolite biosynthesis through microbiome manipulation.

The common hop (Humulus lupulus L.) is a dioecious perennial climbing plant, mainly known for the use of its female inflorescences (cones or, simply, “hops”) in the brewing industry. However, the very first interest towards hops was due to its medicinal properties. Actually, the variety of compounds present in almost all plant parts were (and still are) used to treat or prevent several ailments and metabolic disorders, from insomnia to menopausal symptoms as well as obesity and even cancer. Although hops are predominantly grown for hopping beer, the increasing interest in natural medicine is widening new interesting perspectives for this crop. Moreover, the recent success of the craft beer sector all over the world, made the cultivated hop come out from its traditional growing areas. Particularly, in Europe this resulted in a movement towards southern countries such as Italy, which added itself to the already existing hop industry in Portugal and Spain. In these relatively new environments, a complete knowledge and expertise of hop growing practices is lacking. Overall, while many studies were conducted globally on phytochemistry, bioactivity, and the genetics of hops, results from public research activity on basic hop agronomy are very few and discontinuous as well. The objective of this article is to provide an overview of possible uses, phenology, and agronomic aspects of hops, with specific reference to the difficulties and opportunities this crop is experiencing in the new growing areas, under both conventional and organic farming. The present review aims to fill a void still existing for this topic in the literature and to give directions for farmers that want to face the cultivation of such a challenging crop.

Given the health-beneficial properties of compounds from hop, there is still a growing trend towards developing successful extraction methods with the highest yield and also receiving the products with high added value. The aim of this study was to develop efficient extraction method for isolation of bioactive compounds from the Polish “Marynka” hop variety. The modified two-step supercritical fluid extraction allowed to obtain two hop samples, namely crude extract (E1), composed of α-acids, β-acids, and terpene derivatives, as well as pure xanthohumol with higher yield than that of other available methods. The post-extraction residues (R1) were re-extracted in order to obtain extract E2 enriched in xanthohumol. Then, both samples were subjected to investigation of their antibacterial (anti-acne, anti-caries), cytotoxic, and anti-proliferative activities in vitro. It was demonstrated that extract (E1) possessed more beneficial biological properties than xanthohumol. It exhibited not only better antibacterial activity against Gram-positive bacteria strains (MIC, MBC) but also possessed a higher synergistic effect with commercial antibiotics when compared to xanthohumol. Moreover, cell culture experiments revealed that crude extract neither inhibited viability nor divisions of normal skin fibroblasts as strongly as xanthohumol. In turn, calculated selectivity indexes showed that the crude extract had from slightly to significantly better selective anti-proliferative activity towards cancer cells in comparison with xanthohumol.

ABSTRACT Hop (Humulus lupulus L.) is one of the most important raw materials of beer production. Despite being the third-largest producer and consumer of beer worldwide, Brazil imports almost all hops for production. Nitrogen is an essential macronutrient for hop development and its behavior under different doses is still unknown for Brazilian conditions. Our goal was to evaluate the dry matter and essential oil yields of the Chinook hop fertilized with five N rates during three harvests. Leaves, branches, and cones were sampled to determine their dry matter production, and cones were also analyzed for essential oil contents, extracted by hydrodistillation. Cone number per plant, cone, branch, and leaf dry matter yields, as well as total essential oil yield per plant, increased linearly as nitrogen rates were raised. The production of DM of cones obtained ranged between 245.8 (N:0) and 386.7 kg ha-1 (N:250 kg N ha-1). Yield differences were also noted between harvest years due to weather conditions. Therefore, we can conclude that increasing N rates and climatic conditions affect N contents in hop leaves, as well as hops overall and oil yields, due to the higher cone dry matter. However, essential oil contents in cone dry matter did not change.

A survey was conducted in the Maritimes region of eastern Canada to measure the phytochemical diversity of prenylchalcone, soft resins (alpha & beta acids), and flavonol constituents from 30 unique wild-growing populations of hops ( L.). Based on cone chemometrics, the majority of accessions (63.3%) are native ssp. , with cones containing both xanthogalenol and 4'- -methyl xanthohumol as chemotaxonomic indicator molecules. Interestingly, the leaves of all verified ssp. accessions accumulated high proportions (>0.20 total flavonols) of two acylated flavonol derivatives (kaempferol-3- -(6''- -malonyl)-β-D-glucopyranoside; quercetin-3- -(6''- -malonyl)-β-D-glucopyranoside), both previously unreported from hops leaves. The native accessions examined possess only trace amounts of this compound in their leaves (<0.10 total flavonols), suggesting its potential utility as a novel, leaf-derived chemotaxonomic marker for subspecies identification purposes. A leaf-derived taxonomic marker is useful for identifying wild-growing accessions, as leaves are present throughout the entire growing season, whereas cones are only produced late in summer. Additionally, the collection of cones from 10-meter tall wild plants in overgrown riparian habitats is often difficult. The total levels of alpha acids, beta acids, and prenylchalcones in wild-collected Maritimes cones are markedly higher than those previously reported for individuals in the westernmost extent of its native range and show potentially valuable traits for future cultivar development, while some may be worthy of immediate commercial release. The accessions will be maintained as a core germplasm resource for future cultivar development.

Humulus lupulus L. (hop) is a dioecious climbing plant of which the females bear particular inflorescences, called hops, ‘cones’ or ‘strobiles’, made of a series of membranaceous bracts and bracteoles. At the base of these ‘cones’ occur glandular trichomes where a complex metabolome is synthesized mainly consisting of terpenoids (constituents of essential oil) and original prenylated phenolic compounds. These latter are represented by acylphloroglucinols including α-acids (humulone and its derivatives) and β-acids (lupulone and its derivatives), as well as chalcones (xanthohumol and desmethylxanthohumol). Some of these compounds, terpenoids and sulfur-containing compounds from essential oils and α-acids, are particularly sought after by brewers because they impact bitterness, aroma, flavour and storage properties of beer. Yield of α-acids and bittering performance drove selection of cultivars until demand for alternative flavour options from craft brewers emerged. More aromatic cultivars with intense fruit-like character have been in high demand in recent years due to the trend for hoppy beers and dry hopping. Moreover, there is a tendency toward local consumption associated with craft beer. In addition, consumers and producers are understanding the concepts of sustainability, partially driven by perception of the effects of anthropogenic climate change. Finally, traditional supply chains are facing legitimate challenges from small scale local producers. This review presents the current challenges of hop production and appraises the tools available to investigate the genetic and chemical diversity of this plant.