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HUMULUS LUPULUS L. (HOPS) – A VALUABLE SOURCE OF COMPOUNDS WITH BIOACTIVE EFFECTS FOR FUTURE THERAPIES
Abstract
Hops are a well-known source of resins, essential oils and polyphenolic substances, such as proanthocyanidins or prenylflavonoids with significant representatives of xanthohumol, isoxanthohumol, and 8-prenylnaringenine, and represent an essential ingredient in beer production. Recently, however, many additional bioactive effects of hop compounds have been investigated. A systematic review of the structure-function relationship between the individual hop-derived compounds and their bio-activity has been lacking. In this review we summarize some recent findings in this area from reports from our as well as other studies. It shows multiple bio-medical effects of the individual hop derived compounds, which can act individually, or in a synergistic manner. The hops can serve as a source of bio-active compounds in phyto-medicine and as such, more attention and detailed studies are warranted to utilize the broad spectrum of effects of individual compounds in future treatments.
... The female flowers are called strobile or cones. That are yellowish-green in color and consist of bracts, bracteoles and lupulin glands, which contain abundant resinous essential oil [2,3]. Hops, which grows naturally in Asia (China, Japan), Europe (Germany, Poland, England, Czech Republic, Slovenia), North America (mainly in Idaho, Oregon, and Washington), South Africa, Ukraine, Australia, and New Zealand, is cultivated in various provinces of Turkey such as Bilecik, Kayseri (Erciyes Region) and Kırklareli. ...
... Hops, which grows naturally in Asia (China, Japan), Europe (Germany, Poland, England, Czech Republic, Slovenia), North America (mainly in Idaho, Oregon, and Washington), South Africa, Ukraine, Australia, and New Zealand, is cultivated in various provinces of Turkey such as Bilecik, Kayseri (Erciyes Region) and Kırklareli. It is grown in many regions with abundant sunlight, warm temperatures, high annual precipitation and fertile soil [1][2][3][4][5][6][7][8]. ...
... Hops are traditionally used for healing earache, toothache, stomach problems, liver disorders, leprosy, and fever; especially the female inflorescences have been shown to have biological activity. Traditional Chinese Medicine and Ayurvedic Therapy included H. lupulus to treat problems such as indigestion and nervous tension [2,3,12]. In aromatherapy, H. lupulus applied for skincare, respiratory conditions, nervousness, nerve pain and stress related conditions. ...
... The main compounds occurring in mature female inflorescences of Humulus lupulus are hop bitter acids, terpenes and chalcones. They also contain flavone glycosides (rutin, kaempferol, quercetin, quercitrin, astragalin) and catechins (catechin gallate, epicatechin gallate) (Olšovská et al., 2016;Zanoli and Zavatti, 2008). The composition of hop essential oil includes numerous volatile components, such as monoterpenes (myrcene) and sesquiterpenes (β-caryophyllene, farnesene, humulene), that total up to 57-82% of the entire content. ...
... Due to the extensive range of biological activity of the compounds contained in hop, they are analyzed as potential antioxidants. Polyphenols have a defensive effect or as dyes, they attract pollinating insects (Olšovská et al., 2016). Hop polyphenols may inhibit the processes of ageing of the organism, as those compounds display four-fold greater antioxidant activity than vitamin C, commonly known for those properties. ...
... Other authors also confirmed the diversity of composition between different hop oils, which results from the varietal characteristics and is also shaped by cultivation and technological factors (Nance and Setzer, 2011;Vázquez-Araújo et al., 2013). The hop oil fraction is a complex mixture of volatile aromatic compounds, which are considered essential, because they give hops their characteristic smell (Olšovská et al., 2016). Eri et al. (2000) detected 286 distinct chemical entities in the chromatogram of the hop essential oil. ...
Purpose
Hop cones are valuable raw materials in the brewing industry, as well as in medicine. The aim of the study was to determine the content of selected groups of phytochemical constituents in the pharmaceutical grade herbs of hop cones Humulus lupulus L. and to examine the antioxidant activity of the essential oil (EOHl). In addition, molecular docking was performed to elucidated interactions of different hops cones components with the main enzymes involved in diabetes type II and hypertension.
Methods
Total flavonoids and phenolic contents are spectrophotometrically determined. The content EOHl was determined by hydrodistillation. Volatile compounds were identified by GC-FID and GC-MS. Antioxidant effectiveness of EOHl is examined by DPPH radical scavenging method. Docking study was performed using Molecular Operating Environment software (MOE).
Result and conclusion
The tested hop cones contained up to about 4.20% of total phenolic compounds and up to about 0.37% flavonoids. The content of EOHl reached up to 0.495% v/w with τ-cadinol and α–humulene as the main ingredients. In addition, EOHl contained up to 4.87 mg/ml polyphenolic compounds. The radical-scavenging activity of EOHl ranged from 25.31 mM to 66.99 mM expressed as Trolox equivalents. Docking simulations showed that the most probable potent inhibitors of dipeptidyl peptidase-4, alpha-amylase, alpha-glucosidase, and angiotensin converting enzyme (ACE) were rutin and astragalin with high energy score compared to the reference ligand. From the results obtained it could be predicted that anti-diabetic and antihypertensive potential of hopes cones could be attributed to the presence of rutin and astragalin.
... Hop cones also contain other important compounds, such as polyphenols, which contribute to beer flavour, colour, taste and haze formation and have a strong antioxidant power [3,4]. Hop polyphenols include flavonols (e.g., quercertin and kaempferol), flavan-3-ol (e.g., catechins and epicatechins), phenolic acids (e.g., ferulic acid), prenylflavonoids (xanthohumol, isoxanthohumol, desmethylxanthohumol, 6-and 8-prenylnaringenin), multifidus glycosides and resveratrol [1,5,6]. The polyphenolic fraction of hops is so complex that researchers still continue to identify compounds [1,7]. ...
... Thus, this study aims to carry out a set of experimental trials to test important factors (plant vigour, foliar sprays, liming, cultivar and year) that can influence the quality of the cones and particularly phenol concentration and phenolic composition. A high content of phenols is a positive trait of hop cones, due to their bioactive effect, which contributes to beer quality [4][5][6]. The field trials included four factorial designs exploring the combined effects of (1) plots of different vigour plants and year, (2) plots of different vigour plants, algae-and nutrient-rich foliar sprays and year, (3) plots, liming and year and (4) cultivars and year. ...
The interest in expanding the production of hops outside the traditional cultivation regions, mainly motivated by the growth of the craft brewery business, justifies the intensification of studies into its adaptation to local growing conditions. In this study, four field trials were undertaken on a twenty-year-old hop garden, over periods of up to three years to assess the effect of important agro-environmental variation factors on hop phenol and phenolic composition and to establish its relationship with the elemental composition of hop cones. All the field trials were arranged as factorial designs exploring the combined effect of: (1) plots of different vigour plants × year; (2) plots of different plant vigor × algae- and nutrient-rich foliar sprays × year; (3) plot × liming × year; and (4) cultivars (Nugget, Cascade, Columbus) × year. Total phenols in hops, were significantly influenced by most of the experimental factors. Foliar spraying and liming were the factors that least influenced the measured variables. The year had the greatest effect on the accumulation of total phenols in hop cones in the different trials and may have contributed to interactions that often occurred between the factors under study. The year average for total phenol concentrations in hop cones ranged from 11.9 mg g−1 to 21.2 mg g−1. Significant differences in quantity and composition of phenolic compounds in hop cones were also found between cultivars. The phenolic compounds identified were mainly flavonols (quercetin and kaempferol glycosides) and phenolic carboxylic acids (p-coumaric and caffeic acids).
... Nevertheless, there is still a lot to be investigated, including new food applications and specific effects of hop chemicals, interfering factors of bioactivity, and sensorial aspects associated with hop incorporation. Different reviews have been done on the hops, their role in brewing, their chemical substances, and properties, and also extraction techniques (Astray et al., 2020a, b;Bocquet et al., 2018b;Hrncic et al., 2019;Olšovská et al., 2016;Rettberg et al., 2018;Sanz et al., 2019;Steenackers et al., 2015;Suzuki et al., 2006). However, a specific review covering characteristics of hops, focusing on their potential for different applications in the food industry, giving an update on trends for extraction/ purification of their bioactive compounds, and further prospects for commercial application in food products is not yet available in the literature. ...
... Indeed, recent results indicating high yields of extraction of hop bioactive compounds ("An Update on Extraction and Purification Methods Applied to Hop Compounds") and a wide range of bioactivity (antibacterial, antifungal, cardioprotective, antioxidant, antiinflammatory, anticarcinogenic, and antiviral effects, etc.) of the substances extracted from hops make this plant a valuable source of bioactive compounds (Astray et al., 2020a, b). Also, considering hops pronounced broad spectrum of antimicrobial activity, it can be an interesting alternative against the increasing number of pathogenic strains of bacteria (and viruses) resistant to different types of already used antimicrobials (Olšovská et al., 2016). ...
Hops (Humulus lupulus L.) are known worldwide for their application in the food industry by providing both aroma and flavor to the beer. Considering its popularity as an indispensable brewing crop, a lot of information can be found in the literature about the bioactive compounds present in hop cones. However, current research pointed that hop application can go further than brewing. The present review updates the emerging technologies used to extract hop bioactive compounds in comparison with the conventional ones. The main characteristics, extraction conditions, and extracted compounds of these environmentally friendly extraction methods are highlighted, helping to understand their importance and industrial applications, especially considering hop phytochemicals and their potential for the food industry. In addition, considering this still little addressed potential, this work summarizes the use of hops in different food matrices and emphasizes the relevant aspects that circumvent it. The development of “hopped products” in addition to their potential use as food preservatives expanded the hop industrial perspectives. Among the non-beer foods, meat products, minimally processed vegetables, bread, and premium products, including non-alcoholic beverages, showed up as great options to hop compound incorporation. Consumer perception based on current trends for hopped products also indicates interesting prospects for industrial spread.
Graphical Abstract
... The Slavic tribes were the first to cultivate and use hops for preserving and seasoning beer, beginning in 1500 to 1000 BC. Starting in the 13th century, other countries began to use hops for brewing purposes as well [28]. Pliny (23-79 AD), the great Roman naturalist, referred to hops as "wolf of the willow" because of twinning growth of hops among the willows, proved as "destructive as a wolf to a flock of sheep". ...
... Conferring to the old herbarium for medicinal treatment, hops were used for the treatment of many conditions, like liver disease, foot odor, leprosy, disturbances in sleep, constipation, and for catharsis of blood. Hops alcohol extracts have been utilized in Chinese medicine for pulmonary tuberculosis and acute bacterial dysentery treatment as well as in Ayurvedic therapies in India [28]. ...
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.
... In ancient times, hops were used against leprosy, bad smell of feet, liver diseases, constipation, sleeping disorders, and for blood purification. Moreover, alcoholic extracts of hops have been used in ayurvedic medicine for treating pulmonary tuberculosis and acute bacterial dysentery due to their strong spasmolytic effect on smooth muscle (Blumenthal et al., 2000;Olsovska et al., 2016). ...
... Previous studies (Gerhäuser, 2005;Olsovska et al., 2016;Weber et al., 2019) showed that xanthohumol and lupulones, prevalent hop active compounds, inhibit C. acnes, S. epidermidis, S. aureus, and Streptococcus pyogenes growth. ...
Bacteria belonging to Staphylococcus genus, in particular methicillin-resistant Staphylococcus aureus and multidrug-resistant Staphylococcus epidermidis, together with Cutibacterium acnes are the main strains involved in skin disease. The increase in multidrug-resistant bacteria has revived attention on natural compounds as alternative agents for the treatment management. Among these, hop extract, a hydroalcoholic solution obtained from experimental crops of Humulus lupulus L. variety cascade (hop), displays diverse biological properties including an antimicrobial one. The aim of this study was to evaluate the antimicrobial activity and the capacity to inhibit the biofilm formation of a characterized hop extract against S. aureus and S. epidermidis multidrug-resistant strains and against a C. acnes strain. The hop extract was characterized by (i) phytochemical analysis through a reversed-phase high-performance liquid chromatography (HPLC)–fluorimetric method, (ii) biocompatibility test with Artemia salina L., (iii) cytotoxicity against two cell lines, (iv) docking analysis, and (v) antimicrobial and antibiofilm activities by detection of zones inhibition, minimal inhibitory concentrations (MICs), biomass quantification, and cell viability. The hop extract was biocompatible and non-cytotoxic at all tested concentrations. HPLC analysis revealed significant levels of gallic acid, resveratrol, and rutin. This last compound was the most representative displaying a high affinity against PBP2a and KAS III (Ki values in the submicromolar range). The characterized hop extract showed a good antimicrobial action with MICs ranging from 1 to 16 μg/mL and was able to inhibit the biofilm formation of all tested strains, except for two S. aureus strains. The biofilm formed in presence of the hop extract was significantly reduced in most cases, even when present at a concentration of 1/4 MIC. The live/dead images showed a remarkable inhibition in the biofilm formation by hop extract with a weak killing action. Overall, the tested hop extract is a good candidate to further explore for its use in the prevention of infection particularly, by multidrug-resistant Gram-positive pathogens.
... In this context, natural compounds have shown promise due to their antimicrobial, antiviral and also anticarcinogenic or (chemo)preventive effects [1,2]. Hop contains a huge variety of prenylated phenolic compounds [3][4][5][6]. The most abundant prenylated chalcone in hops is xanthohumol (XN) [7]. ...
... Dietz et al. showed an efficacy improvement of bioactive hop compounds linked to the concentration of minor compounds in the natural extract [5]. Interestingly, many of these seem to be even more bioactive in comparison to XN [4,7,24,25]. 8-prenylnaringenin is known as one of the most potent phytoestrogen [6], desmethylxanthohumol shows e.g. anti-oxidant activity [26], isoxanthohumol inhibits angiogenesis [27], and 6-prenylnaringenin has anti-fungal activities against Trichophyton spp. ...
Minor prenylated hop compounds have been attracting increasing attention due to their promising anticarcinogenic properties. Even after intensive purification from natural raw extracts, allocating certain activities to single compounds or complex interactions of the main compound with remaining impurities in very low concentration is difficult. In this study, dose-dependent antiproliferative and cytotoxic effects of the promising xanthohumol (XN) analogue xanthohumol C (XNC) were evaluated and compared to XN and a XN-enriched hop extract (XF). It was demonstrated that the cell growth inhibition of human breast cancer cell line (MCF-7) significantly increases after being treated with XNC compared to XN and XF. Based on label-free data-dependent acquisition proteomics, physiological influences on the proteome of MCF-7 cells were analyzed. Different modes of action between XNC and XN treated MCF-7 cells could be postulated. XNC causes ER stress and seems to be involved in cell-cell adhesion, whereas XN influences cell cycles and DNA replication as well as type I interferon signaling pathway. The results demonstrate the utility of using quantitative proteomics for bioactivity screenings of minor hop compounds and underscore the importance of isolating highly pure compounds into their distinct forms to analyze their different and possibly synergistic activities and modes of action.
... The hop essential oils give hops the characteristic smell and provide flavor and aroma to beer. The content and chemical profile of hop essential oil varies greatly depending on variety 9 , geographical location, harvest timing and cultivation factors 10,11 , duration and conditions of storage 12 . On the other hand, gas chromatographic GC analysis of hops essential oil is used as a tool for identification of hop varieties 13,14 . ...
... The hop essential oil contains numerous aromatic compounds. According to recent reports, the number of identified and actually present compounds in the hop essential oil ranges from 485 to up 1000 9,17,18 . The antimicrobial effects of hop compounds have been demonstrated against Gram-positive cocci, parasites, several fungi and protozoa, which is linked to αand β-acids or bitter acids activity 19 21 . ...
The profile and bioactivity of hops (Humulus lupulus L.) essential oil, a complex natural product extracted from cones via steam distillation, depends on genetic and environmental factors, and may also depend on extraction process. We hypothesized that compound mixtures eluted sequentially and captured at different timeframes during the steam distillation process of whole hop cones would have differential chemical and bioactivity profiles. The essential oil was collected sequentially at 8 distillation time (DT) intervals: 0-2, 2-5, 5-10, 10-30, 30-60, 60-120, 120-180, and 180-240 min. The control was a 4-h non-interrupted distillation. Nonlinear regression models described the DT and essential oil compounds relationship. Fractions yielded 0.035 to 0.313% essential oil, while control yielded 1.47%. The oil eluted during the first hour was 83.2%, 9.6% during the second hour, and only 7.2% during the second half of the distillation. Essential oil (EO) fractions had different chemical profile. Monoterpenes were eluted early, while sequiterpenes were eluted late. Myrcene and linalool were the highest in 0-2 min fraction, β-caryophyllene, β-copaene, β-farnesene, and α-humulene were highest in fractions from middle of distillation, whereas α- bergamotene, γ-muurolene, β- and α-selinene, γ- and δ-cadinene, caryophyllene oxide, humulne epoxide II, τ-cadinol, and 6-pentadecen-2-one were highest in 120-180 or 180-240 min fractions. The Gram-negative Escherichia coli was strongly inhibited by essential oil fractions from 2-5 min and 10-30 min, followed by oil fraction from 0-2 min. The strongest inhibition activity against Gram-negative Yersinia enterocolitica, and Gram-positive Clostridium perfringens, Enterococcus faecalis, and Staphylococcus aureus subs. aureus was observed with the control essential oil. This is the first study to describe significant activity of hops essential oils against Trypanosoma brucei, a parasitic protozoan that causes African trypanosomiasis (sleeping sickness in humans and nagana in other animals). Hops essential oil fractions or whole oil may be used as antimicrobial agents or for the development of new drugs.
... Another example of prevailing components in pharmaceutical samples was the bract multicellular glands of matured female flowers (female cones) from hop Humulus lupulus L, which served as a natural sedative drug to calm the nerves, International Journal of Spectroscopy 5 reduce stress and anxiety, or even give anticancer effects [10,11,17,18]. Active matters in hops are bitter acids humulone and lupulone, weak acid components. ...
... A phytoestrogen 8prenylnaringenin has been recently discovered in the female flowers of hops plants [17]. In many cases, extracts of the H. lupulus cones may also act as a prooxidants due to the presence of flavonoids [18,19] and have antitumor potential [20]. All active hop components are accumulated in the multicellular glands (our stereomicroscopic images in Figures 3(a)-3(c)) that, maturing, release small glandular cells named as lupulin in pharmacy (Figures 3(b) and 3(c)). ...
Autofluorescence of secondary compounds contained in plant secretory cells may be applied to the analysis of medicinal plants for pharmacy. Emission and prevailing fluorescent pharmaceuticals have been estimated in several models of species such as Salvia officinalis , Berberis vulgaris , Humulus lupulus , and Matricaria chamomilla , by luminescence microscopy, microspectrofluorimetry, and confocal microscopy.
... They differ significantly in their color, aroma, taste, alcohol content, esters, etc. Hops (Humulus lupulus) are the most expensive (Walters, 2004) and very important raw materials for brewing. In addition to their bitter and aromatic properties, they also act as preservatives of beer (Olsovska et al., 2016). Hops secondary metabolites include hop resins, essential oils and polyphenols (Almaguer et al., 2014). ...
Experiments have been conducted to determine the effect of a higher hopping degree of wort (120 mg/l and 200 mg/l bitter α-acids) on the antioxidant capacity of ale beer. In one of the experimental variants, dry hopping with aromatic hop pellets (3 g/l) was applied. The higher hopping degree of wort did not lead to disturbance in the fermentation process. For beers containing 200 mg/l α-acids, the most significant was the increase in flavonoids (20.6-23.8%) compared to the variant with 120 mg/l α-acids. The polyphenols in highly hopped beer were increased by 6.6-7.1% compared to moderately hopped beer. The content of anthocyanins was not significantly affected by the addition of more hops. Antioxidant activity, expressed as equivalent vitamin C mmol/l, showed an increase of 4-5.2% for highly hopped beers compared to the control variant; when calculated relative to vitamin E, the increase was 5.8-7.5%. All beers were light, with excellent clarity and enhanced hop aroma.
... To date, more than 1000 different compounds have been identified in hop EO, which are considered "essential" because they give hops their characteristic aroma and help define the taste of beer. On average, dried hops contain 0.5 to 3.0 percent EOs [97], and both their amount and composition depend largely on genetic factors, the age of the plant, characteristics of the growing soil, but also on climatic conditions (temperature, humidity, hours of sunshine) and time of harvest [98]. Their biosynthesis, which takes place in trichomes, occurs more slowly than that of resins; consequently, hop oils are fully developed in the last stage of hop maturation [27]. ...
The medicinal potential of hop (Humulus lupulus L.) is widely cited in ancient literature and is also allowed in several official pharmacopoeias for the treatment of a variety of ailments, mainly related to anxiety states. This is due to the plethora of phytoconstituents (e.g., bitter acids, polyphenols, prenyl flavonoids) present in the female inflorescences, commonly known as cones or strobili, endowed with anti-inflammatory, antioxidant, antimicrobial, and phytoestrogen activities. Hop has recently attracted the interest of the scientific community due to the presence of xanthohumol, whose strong anti-cancer activity against various types of cancer cells has been well documented, and for the presence of 8-prenyl naringenin, the most potent known phytoestrogen. Studies in the literature have also shown that hop compounds can hinder numerous signalling pathways, including ERK1/2 phosphorylation, regulation of AP-1 activity, PI3K-Akt, and nuclear factor NF-κB, which are the main targets of the antiproliferative action of bitter acids and prenylflavonoids. In light of these considerations, the aim of this review was to provide an up-to-date overview of the main biologically active compounds found in hops, as well as their in vitro and in vivo applications for human health and disease prevention. To this end, a quantitative literature analysis approach was used, using VOSviewer software to extract and process Scopus bibliometric data. In addition, data on the pharmacokinetics of bioactive hop compounds and clinical studies in the literature were analysed. To make the information more complete, studies on the beneficial properties of the other two species belonging to the genus Humulus, H. japonicus and H. yunnanensis, were also reviewed for the first time.
... Millions of people around the world have experienced high levels of stress as well as chronic degenerative diseases (cardiovascular, obesity, and type II diabetes among others), in relation to that they affect health condition, busy life and bad eating habits. Because this condition has increased in the last decade, people are closer to consume functional foods and beverages (Biendl & Pinzl, 2009;Olsovska et al., 2016;Rietjens, Louisse, & Beekmann, 2017). As hops have been used since ancient times as folk medicine, these functional properties are a topic of interest. ...
... Long and warm days are needed to ensure a successful flowering and thus a suitable cones yield, as well as winter temperatures of approximately 4°C or less are necessary to satisfy the cold requirements of the crop, which is variety dependent, for a period of one to two months (11). Although the utilisation of hop strobiles is almost entirely related to the brewing industry (2), the earliest uses were for culinary (young shoots) and medicinal purposes (12) due to their counteracting effects on microbes and viruses (13). In the modern brewing industry, hop has become a crucial element for the characterization of brewing products. ...
Humulus lupulus L. is a dioecious herbaceous perennial plant with a climbing habit, whose female inflorescences, commonly known as cones, produce and accumulate bitter substances and essential oils. The present study aimed to assess the adaptability of some American hop varieties (Cascade, Chinook, and Comet) in the Mediterranean environment of the Calabria region (Italy) through the evaluation of the morpho-biological and productive characteristics and the characterization of the aromatic traits of the inflorescences. Comet proved to be the most productive variety, while Chinook the earliest. Essential oils obtained by hydrdistillation were analysed by GC-FID and GC-MS. Myrcene, β-caryphyllene and α-humulene were the main components. The combination of morphological traits and the aromatic profiles could be adopted as tools to discriminate varieties. Comet was the most productive variety, while Chinook emerged as the earliest one. Concernng the essential oils Cascade and Comet showed similar profiles, Chinnok was different especially for the sesquiterpenes content.
... We previously demonstrated that a mixture of valerian and Cascade hops increases non-rapid eye movement sleep due to an increase in delta waves via GABA A receptors (Choi et al., 2018). Additionally, hops are used as antiinflammatory, antiseptic, antidiuretic, sedative, and topical skin ulcer treatments (Olšovská et al., 2016;Zanoli & Zavatti, 2008). ...
... Lupulone was isolated from soft resin fraction of hops in a 3% (m/m) yield after extraction and chromatographic purification, according to Taniguchi's method [15,16]. The 3-Isobutyl-5,5,7-tris(3-methylbut-2-en-1-yl)-1-phenyl-1,7-dihydro-4H-indazole-4,6(5H)dione was obtained through a solvent-free reaction under conventional heating between lupulone and phenyl-hydrazine, in the presence of SiO 2 /ZnCl 2 (30% m/m) solid support [17]. ...
Here we describe the functionalization of lupulone natural compound in obtaining 3-isobutyl-5,5,7-tris(3-methylbut-2-en-1-yl)-1-phenyl-1,7-dihydro-4H-indazole-4,6(5H)-dione. The lupulone-H-indazole derivative was prepared with 75% yield through the reaction between lupulone and phenyl-hydrazine employing SiO2/ZnCl2 (30% m/m) as a support solid in a solvent-free condition. Based on the possibilities of products, a complete NMR structural characterization of this lupulone-H-indazole was performed by 1H, 13C{1H}, COSY, HSQC and HMBC NMR experiments, showing an important contribution in producing the first results related to lupulone reactivity.
... Schematic presentation of the cone segment is shown in Figure 7. As is well known, the hop cone consists of bracts and bracteoles which are leaf like structures that surround the entire cone, attaching to a central axis or spindle [25]. In our conducted study the average cone length of the examined hop populations was 41.6 mm in 2018 and 40.7 mm in 2019, longer compared to the results obtained on Italian wild hop accessions, which were only up to 37.0 mm long [24]. ...
... Xanthohumol from Humulus lupulus inhibited HIV-1 induced viral reverse transcription in C8166 lymphocytes (Wang et al. 2004). Xanthohumol also present antiviral activity against herpes simplex virus (Olšovská et al., 2016). ...
Diversified members of hop bitter acids (α- and β-acids) have been found in hop (Humulus lupulus). Mixtures of hop bitter acids have been traditionally applied in brewing and food industries as bitterness flavors or food additives. Recent studies have discovered novel applications of hop bitter acids and their derivatives in medicinal and pharmaceutical fields. The increasing demands of purified hop bitter acid promoted biosynthesis efforts for the heterologous biosynthesis of objective hop bitter acids by engineered microbial factories. In this study, the updated information of hop bitter acids and their representative application in brewing, food, and medicine fields are reviewed. We also speculate future trends on the development of robust microbial cell factories and biotechnologies for the biosynthesis of hop bitter acids.
Key points
• Structures and applications of hop bitter acids are summarized in this study.
• Biosynthesis of hop bitter acids remains challenging.
• We discuss potential strategies in the microbial production of hop bitter acids.
... Schematic presentation of the cone segment is shown in Figure 7. As is well known, the hop cone consists of bracts and bracteoles which are leaf like structures that surround the entire cone, attaching to a central axis or spindle [25]. In our conducted study the average cone length of the examined hop populations was 41.6 mm in 2018 and 40.7 mm in 2019, longer compared to the results obtained on Italian wild hop accessions, which were only up to 37.0 mm long [24]. ...
This study aims to do a morphological and biochemical characterization of selected wild hop populations from the Banja Luka region, as plant material with potential value for introduction into plant selection. Female inflorescences (cones) from seven populations (DKH3, DKH5, DKH6, DKH8, DKH9, DKH10, and DKH11) were sampled in 2018 and 2019. Hop cones were collected in October 2018 and 2019 for morphological characterization, when 50 cones per population were analyzed, and also the cones were collected in mid-September in 2019 for biochemical characterization. Morphological parameters were carried out for: cone length (cm), number of nodes per cone spindle, cone density, and number of seeds per cone, all important agronomic characters in hop production. Also, 27 components of essential oil and 6 components of hop resins were analyzed. Statistical analysis of morphological characteristics was performed by factorial analysis of variance (year × population), and the significance of individual differences was determined by LSD test. The grouping of examined hop populations according to the manifested morphological characteristics was performed by cluster analysis. Statistical analysis for biochemical characteristics was performed by analysis of variance, and the significance of the differences was tested by Tukey’s statistical test. In order to determine similarities between different population multivariant statistical method Principal component analysis (PCA) was applied. According to morphological and biochemical analysis, DKH6 hop population is singled out as the most valuable for hop breeding.
... Subsequently, hops were associated with sedative, soothing, digestive, antioxidant, anticancer, and other health positive properties. [109][110][111] At present, several hop health benefits have been investigated. Those that are attributed to the essential oil are shown in Fig. 5, and some of them will be described in greater detail. ...
Hop cones (Humulus lupulus L.), or more specifically the lupulin glands, hold the reason for the specific, pleasant aroma of hops – its essential oil. The hops themselves, or the extracted oil, are used almost exclusively in beer production. The essential oil is an indispensable part of beer and is responsible for its characteristic aroma. However, hop essential oil (HEO) also has a broad range of positive effects on human health and is a potential natural pesticide that has no harmful impacts on humans. This review summarizes basic information about HEO, including its chemical composition and methods for extraction and analysis, while also providing a comprehensive overview of the contribution to beer aroma, health, and insecticide applications for this versatile essential oil.
... Hops stipule extracts can be successfully used to prevent caries and periodontal diseases [15]. Moreover, various parts of this plant favorably affect urinary and digestive system, reduce cholesterol level, risk of ulcers development and high blood pressure, seal blood vessels and have a positive effect in relieving rheumatic pains [2,7,11,12,16]. ...
Introduction: Hop ( Humulus lupulus L.) is a common plant in Europe, with many beneficial health effects. In addition to the use in brewing, hops are a valuable source of active substances used in conventional and folk medicine, such as humulones and lupulones, as well as antioxidants, including phenolic compounds.
Objective: The aim of the study was to evaluate and compare the antioxidant activity of alcoholic extracts of fresh hop leaves collected in 2017 and 2018.
Material and methods: The raw material consisting of fresh hop leaves was extracted using ultrasound-assisted extraction. Methyl, ethyl and isopropyl alcohol at three concentrations were used as extractants. The antioxidant activity of extracts was determined using DPPH and FRAP methods. Total phenolic content was evaluated using the Folin-Ciocalteu technique.
Results: All the extracts showed antioxidant potential as well as the phenolic content. Regardless of the harvesting year and methods of evaluation, the highest antioxidant activity and the total polyphenol content were observed for extracts prepared in undiluted methanol, obtained during one hour lasting extraction.
Conclusion: The results of the studies have suggested that hop leaves can be a potential source of health-promoting antioxidants.
... In fact, cones contain the lupulin glands that produce important phytochemical compounds (α-and β-acids, essential oils, and polyphenols) which contribute to determine the bitterness, flavour, aroma, and antimicrobial properties of beer (Benitez et al., 1997). They are also used for medicinal purposes as sedatives, tonics and for soothing and calming effects on the body and minds (Zanoli and Zavatti, 2008;Olsovska et al., 2016). On the contrary, male plants are generally used by breeders to hybridise and develop new varieties. ...
Land suitability assessment is an efficient method used to give indication about a sustainable land use planning. A decision support system based on multi-criteria analysis was used to evaluate land suitability for hop cultivation in four regions of Central and Southern Italy (Abruzzo, Basilicata, Latium and Molise). Seven environmental parameters (altitude, average minimum temperature between November and February, average maximum summer temperature, spring rainfall, summer rainfall, organic carbon content, and environmental sensitive area index) were considered to generate the suitability index. The analysis revealed that Abruzzo and Latium are more suitable for hop cultivation than Basilicata and Molise: only 7% municipalities for Latium and 11 % for Abruzzo were unsuitable for this cultivation. On the other hand, more than 50 % of Basilicata and 33 % of Molise resulted not suitable. Results provided an effective tool to evaluate physical land suitability and, consequently, to choose the adoption of a proper management and farming systems, which could allow the hop cultivation even in not potentially suitable areas.
... Among others, the hop plant (Humulus lupulus L.), with its long history in traditional medicine, has been used in the treatment of many conditions including bacterial infections, and also for its qualities as a preservative 7 . Recent studies describe biological activities of hop metabolites, including their antibacterial, antifungal and antiviral activities and their future therapeutic potential [8][9][10][11] . So far, the reported antibacterial activity is mainly against Gram-positive bacteria. ...
Aim:
Our research focused on the antimicrobial effects of purified hop (Humulus lupulus L.) fractions including α-bitter acids (humulones), β-bitter acids (lupulones) and xanthohumol, and a commercial CO2 hop extract of bitter acids against reference and multi-resistant strains of Gram-positive and Gram-negative bacteria and against selected yeast strains.
Methods:
In vitro testing of antimicrobial activity was performed according to standard testing protocols (EUCAST). The effects of hop extracts on bacterial/yeast strains at concentrations below MICs were also determined and the antimicrobial potential of hop extracts was compared with selected antibiotics using optical density measurement.
Results:
The fractions were effective not only against reference strains of Gram-positive bacteria but, more importantly, against their methicillin- and vancomycin-resistant variants. No antimicrobial effect was detected against Gram-negative bacterial strains. Among the tested substances, xanthohumol was identified as the hop fraction with the most potent antimicrobial properties. It was also found that hop substances exerted their antimicrobial effects at concentrations considerably lower than the determined MICs, with the strongest effect in case of α-bitter acids in enterococci.
Conclusion:
The search for and research of new compounds with antimicrobial properties represents a possible solution to the current global problem of bacterial resistance. Our data suggest a desirable activity of hop fractions against some multi-resistant bacterial strains. Thus, hops might find use as a source of potential antimicrobial agents applicable in both human and veterinary medicine.
... Moreover, apart from the known role in brewing beer, hops are also used in herbal remedies as a treatment to cure diseases or ailments like anxiety, inability to sleep (insomnia and other sleep disorders), restlessness, tension, excitability, nervousness, and irritability [1]. Olšovská et al. [2] summarized the known biological activity of all three basic groups of hops secondary metabolites (resins, essential oils and polyphenols), however, there is a lack of information about antimicrobial activities of individual hop compounds. ...
We hypothesised that QuEChERS could be successfully applied to the extraction of bitter acids and xanthohumol from hops, which would be less time consuming, cheaper, and more eco-friendly by the severe reduction of solvent use. High performance liquid chromatography was used to separate the compounds after extraction and quantitation was evaluated against standard calibration curves for bitter acids prepared from an International calibration extract (ICE-4) and an authentic standard of xanthohumol. The standard QuEChERS method was compared to mini and micro-versions including clean-up and spiking procedures. The quantitative analyzes indicate the applicability of the QuEChERS method for the quantitation of bitter acids compared to Soxhlet extraction. The statistical data confirm reproducibility of the total alpha- and beta- acids measured by the standard method and the modified mini- and micro-QuEChERS procedures. Our hypothesis is supported by the data described and is consistent with other previous methods described in the literature.
This study investigated the use of conventional and innovative extraction methods to produce food-grade hop extracts with high antioxidant capacity and content in bioactive compounds. Conventional extractions (CONV) were performed under dynamic maceration at 25 and 60 ◦C; innovative extractions were performed using two ultrasound systems, a laboratory bath (US) and a high-power ultrasound bath (HPUS), and a high-pressure industrial process. For CONV, US, and HPUS extractions the effect of the extraction time was also tested. Experimental results showed that extraction method, temperature, and time affect to a different extent the phenolic profile and have a significant effect (p < 0.05) on the total phenolic content, total flavonoid content, antiradical capacity (ABTS), chlorophyll α, and total carotenoids content. Overall, US and CONV 60 ◦C extractions showed the highest extraction efficiency for almost all the investigated compounds, however, the extraction method and time to be used strongly depends on the target compounds to extract.
Tarhana, a traditional food in Turkish cuisine, is produced using lactic acid fermentation. In this study, hops (Humulus lupulus L.) was added to tarhana samples during the process phase, and physicochemical, sensory and antimicrobial analysis results were compared with the control samples. The means of pH, Titration Acidity, Dry Matter Amount, Ash Amount, Protein Amount, Fat Amount, and Starch Amount ratios were determined. The samples’ N, P, K, Mg, Ca and Fe contents were high. The raw materials used in the samples did not affect the colour values significantly. The most liked sample in terms of sensory experiences was the Sample‐W4 with the highest rate of wet hops. Antimicrobial activity tests showed that most of the samples had a significant effect against gram positive/negative bacteria and yeast strain. Comparison of the analysis parameters with the independent samples t‐test analysis suggested a difference between all the results obtained (p<0.05).
Dental pathology is represented by a wide range of diseases of hard and soft tissues of these organs, various types of injuries, anomalies of shape, number, location, periodontitis. Inflammatory periodontal diseases are one of the most common human diseases, which lead to significant socio-economic losses and reduced quality of life. At the beginning of the XXI century, prevention and treatment of inflammatory periodontal diseases remains an urgent problem of medicine. The high frequency of periodontal lesions is largely due to the peculiarities of its structure and function, general human health, the constant influence of microorganisms, among which the dominant role is played by opportunistic and pathogenic bacteria. The microflora in inflammatory periodontal diseases differs from the microflora of the oral cavity of a healthy person by the presence of peculiar symbiotic associations with a specific dominant species of the pathogen. The main element of the modern protocol of medical care for periodontal disease is the systemic or local use of antimicrobials. Modern antibiotics and chemotherapeutics used in dental practice for the treatment of CPD, totally affect all parts of the biocenosis of the oral cavity and lead to its undesirable changes. In addition, even a short-term positive effect of the use of these drugs can be combined with a selective increase in the resistance of pathogens to antibacterial drugs, which generally reduces the expected effectiveness of traditional therapy. Inflammatory periodontal diseases, prospects of their treatment by classical methods and with the use of modern medical technologies were studied in the work. For the objectification of the study used archival materials and their own work over the past 15 years. The purpose of the study: to identify promising areas of integrated use of traditional and innovative treatments for inflammatory periodontal disease. The subject of the study was to clarify the issues of antibacterial, antifungal activity of hop products, the rate of formation of resistance in microorganisms, the adequacy of physical, physicochemical properties of gel compositions. Particular attention was paid to the use of antibacterial properties of gel compositions based on hop products. It is established that the use of antibiotics and chemotherapeutics in modern medical practice for the treatment of inflammatory periodontal diseases has a number of significant limitations due to the short duration of their therapeutic effect, negative impact on human microbiocenosis and the formation of acquired resistance of pathogenic microflora to widely used drugs. The results of previous studies have demonstrated the prospects of herbal medicines, namely, created on the basis of hop products for the prevention and treatment of diseases of microbial origin. It was found that the antibacterial and antifungal action of gel preparations of optimal composition with EHV 0.5% significantly exceeds the specified indicators of such known and currently used drugs. Therefore, it is clear the scientific and practical meaning of the use in protocols for the treatment of inflammatory periodontal diseases (as drugs for local therapy) phytomedicine based on hop herbal substance. Thus, a clear prospect of using new compositions of drugs with high antibacterial properties based on plant raw materials (including hops) for the treatment and prevention of periodontal disease. Solving this problem is a timely and socially appropriate fact.
Acne is a leading player in the spread of skin diseases. Epidemiological studies conducted in industrialised Western countries have estimated the prevalence of acne in adolescents at between 50% and 95%, depending on the method used to calculate the lesions. Acne, a disease that most often befalls teenage faces, occurs in children after the onset of adrenal and gland androgens production and subsides after growth. However, it may continue to manifest itself in a large proportion of adults, especially women. Even after recovery, negative effects such as scars and pigment spots remain. Acne (L.70, eels, ICD-10) is a chronic polymorphic multifactorial inflammatory disease of the sebaceous glands and periglandular tissue that develops mainly in young people. To date, the causes of etiopathogenesis of BX have not been sufficiently investigated. According to ICD-10, the following factors are important in the development of the disease: 1) increase in skin fat production 2) excessive follicular hyperkeratosis; 3) microflora (Propionibacterium acnes) influence 4) inflammation development. Patients suffering from acne have significantly increased skin fat production, which is usually correlated with the severity of the disease. Changes in the physiological state of the seborrhea glands, which is the basis of seborrhea, develop under the influence of neuroendocrine system dysfunction. Hyperplasia and sebaceous gland hyper-secreting occur, the physical and chemical composition of seborrhea changes and its bactericidal properties are reduced. The imbalance of the autonomic nervous system is important, which leads to a temporary or permanent increase in the tone of the vagus innervation of the sebaceous glands and, as a result, hyperproduction of sebum. A number of researchers consider follicular hyperkeratosis to be one of the leading links in the pathogenesis of acne. The aim of the study was to study the chronic toxicity of a gel with an extract of carbon dioxide hops and to determine the effect of the latter on organ changes in laboratory animals. The methodological basis was microbiological, cultural, morphological and biochemical research methods. The duration of observation was 30 days. Both experimental prototypes of gel preparations and placebo were studied in the study groups. The results in the experiments were compared with intact controls. In an animal experiment (laboratory rats), it was found that gels with carbon dioxide hop extract do not exhibit toxic (chronic) effects on the body. Dynamics of the body mass of the individuals studied, blood parameters, including the constituent elements of the blood serum, CNS functioning parameters, structural and functional state of the urine and kidney systems are the objective evidence base for the use of the medicinal substance after the clinical stage of the studies. Based on the results of a pathomorphological study of the internal organs of experimental animals, it was established that the acne gel for long-term use in the studied dose does not affect the relative mass of the internal organs of rats and does not cause morphological and functional changes in them, does not lead to inflammatory reactions, destructive and degenerative processes and necrosis. Thus, the results of this study provide the basis for the treatment of acne with mudflow medications through their prolonged use. It has been determined that the gel does not have toxic effects on the skin and does not lead to negative effects on the internal organs of animals.
In the present study, natural deep eutectic solvents were used to increase the extraction efficiency (EE) of bioactive compounds from hop (Humulus lupulus L) cones under ultrasounds irradiation. Three lactic acid-based deep eutectic solvents (namely LaDES) were developed, physicochemical characterized and their EE values compared with those of a control extract, obtained using aqueous methanol (80%) acidified with HCl (0.1%). The supramolecular organization of LaDES and their extracts were analysed using FTIR spectroscopy and Raman spectroscopy to clarify the interactions among LaDES components and between LaDES and the bioactive components of the plant matrix. The phytochemical profiles of green extracts were evaluated using both spectrophotometric assays and HPLC-DAD analysis and the results were compared with those from the control samples. Among the different combinations of LaDES tested, lactic acid: sucrose showed the highest EE against hop bitter acids (-acids: 8.9 0.1 % w/w; -acids: 3.2 0.3 % w/w), while lactic acid: urea extracted more non-phenolic pigments (total chlorophyll: 8.79 0.09 mg g-1 d.b.; total carotenoids: 2.22 0.02 mg g-1 d.b.) than the other two LaDES combinations and control. Polyphenols were better extracted by lactic acid: glycine than the other solvents tested (71.2 0.1 mg gallic acid equivalents g-1 d.b.), also showing the highest antiradical potential against both ABTS+• and DPPH• (EC50_ABTS: 0.63 0.01 g; EC50_DPPH: 69 2 g). Finally, all LaDES inhibited both Gram- positive and negative bacteria, while non activity was recorded against tested yeasts.
Currently, there is a continuous growth in demand for medicinal and aromatic plant derived molecules obtained in a sustainable and eco-friendly way. Among the medicinal plants that have a plethora of health-related properties, there is definitely hops. In the present study, microwaves (MW) and ultrasounds (US) were used to increase the extraction efficiency of bioactive compounds from hop cones using water, ethanol and their mixture as food-grade solvents. A multidisciplinary approach was used for the in-depth characterization of green extracts. The bioactive components were determined by chemical methods, using both spectrophotometric assays as well as high-performance liquid chromatography with diode-array detection (HPLC-DAD) analysis of individual phenols, bitter acids and xanthohumol, and results were compared with those from a control extract, obtained using aqueous methanol (80 %) acidified with HCl (0.1 %). Moreover, we applied proton nuclear magnetic resonance (1H-NMR) spectroscopy to reveal insights on the different composition in terms of primary and sec- ondary metabolites of the green extracts analyzed. Generally, microwave-assisted extraction (MAE) of hop cones with ethanol showed the strongest extraction power for almost all the bioactive compounds investigated, as well as the shortest extraction time (1 min) and the highest antiradical capacity. 1H-NMR analyses showed an overall greater influence of solvent polarity, rather than extraction technique, on the average composition of the final extract. 1H-NMR fingerprinting of hop aqueous extracts highlighted as main components sugars and amino acids, as well as other metabolites including trigonelline, an alkaloid with interesting biological properties. However, the two extraction techniques significantly affected the contribution of signals in the terpene or aromatic regions when ethanol and ethanol:water were used as solvents, proving a better extraction efficiency for these com- pounds of MW than US. Regardless the extraction technique and solvent used, the most abundant polyphenol compound in the green extracts analyzed was catechin, ranging from 2989 ± 10 to 14009 ± 248 μg g− 1 (for UAEETOH and MAEETOH, respectively), followed by rutin and chlorogenic acid. 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-Azinobis [3-ethylbenzothiazoline-6-sulfonic acid]-diammonium salt (ABTS) radical scav- enging methods were used to evaluate the biological properties of green hop extracts, showing a superior free- radical scavenging capacity in MW irradiated ethanol samples compared to other samples tested. The inter- relationships between the parameters analyzed and the different extraction conditions, as well as the relation- ships among variables, were investigated by principal component analysis.
The goal of the research was to assess the inhibitory effects of hop extracts, iso-α and β acids, against Pediococcus pentosaceus bacteria, during a short incubation period, both in liquid selective media (high pH values) and beer wort fermentation (low pH values) and testing if the identified iso-α acid stress changes the activity of S. cerevisiae boulardii yeast and ethanol production. Flow cytometry analysis was used for bacterial and yeast cell viability. In relation to the antibacterial activity of β-acids, a lower viability of Pediococcus pentosaceus cells was observed after a short incubation period in selective media, under iso-α acid stress. In beer wort, for a mixed culture with P. pentosaceus bacteria and S. cerevisiae boulardii yeast, under iso-α acid stress conditions at pH 4.0-5.0, Pediococcus pentosaceus exhibited lower cell viability (20.7%) than in selective media (61.4%). Regarding iso-α hop acid on S. cerevisiae boulardii yeast, the results showed that iso-α does not change the S. cerevisiae activity but prevents the culture from being contaminated by Pediococcus pentosaceus. The results highlighted reliable inhibitory effects of iso-α and β-acids against P. pentosaceus, both at pH 6.0-7.0 and pH 4.0-5.0, which open the possibility of hops being used as a supplement to prevent beverage contamination with spoilage microorganisms. ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********
Brucellosis is an old, infectious and common zoonosis whose causative agents are Gramnegative bacteria from the Brucella genus. Brucellosis is transmitted through direct contact with infected animals or using unpasteurized dairy products of goats, pigs, camels, sheep, buffalo and cows. Brucellosis is still the most common zoonosis in the world, with most of cases occurring in developing countries. Today, an approach to traditional medicine and medicinal plants, especially with regards to the repeated recommendations of the World Health Organization, is a necessity. One-third of chemical drugs are produced by using plants and there is a high potential to produce more drugs from plants. Medicinal plants are helpful in the management of various conditions, especially bacterial diseases. Although there is not enough scientific evidence regarding the clinical effectiveness of herbal drugs for the treatment of brucellosis, there is strong evidence on the antimicrobial effects of herbal drugs to prevent infection. Therefore, this article seeks to describe the antibacterial effects of some plant-derived essential oils or extracts, so that they can serve as promising choices to develop new anti-Brucella medications, as suitable alternatives to conventional antibiotics for brucellosis, as much as possible, taking into account the benefits of these herbal drugs.
The presence of proanthocyanidins, substances belonging to the general group of polyphenols in beer is generally rather undesirable due to their tendency to form complexes with proteins, and thereby degrade the colloidal stability of beer. On the other hand, these substances are useful because of their ability to bind free radicals and thereby improve sensory stability of beer. The knowledge of the profile of the proanthocyanidins in beer and raw materials and their individual behavior during the entire technological process could help to address the challenges associated with improving the sensory and colloidal stability of beer. Therefore, we have developed a novel method for determination of proanthocyanidins by liquid chromatography with high resolution mass detection. The method was used to monitor changes in the profile of selected proanthocyanidins during the brewing process and consequently to verify the specificity profile of proanthocyanidins for given variety of Czech hops.
The goal of this work was to provide evidence for the inhibitory effects of fresh hops on the growth of Helicobacter pylori. Fresh hops were homogenised after harvest and the homogenate was treated using pascalisation (treatment with high pressure). This homogenate was used for testing the growth inhibitory effects on strains of H. pylori, a pathogenic microorganism, isolated from patients suffering from gastritis or gastric ulcers. The tests demonstrated reliable inhibitory effects and open the possibility of hops being used as a supplement to the treatment of H. pylori infections.
Linalool, an important substance in hoppy, aromatic beer, is one of the
most aromatic components of essential oils in hops. Linalool concentration,
among those of other substances, could be used to distinguish
among hops varieties. As such, an effective, repeatable, and high-throughput
method is required; a new method based on fluidized-bed extraction
combined with detection by gas chromatography–mass spectrometry was
developed and is presented in this study. This method is faster than the
reference method, which uses steam distillation; it also reduces the possibility
of thermal changes. Because this method saves organic solvent,
energy, and sample amount, it can be considered a green method. Good
repeatability of the method (8.0 mg/kg) was achieved with 3-hepten-1-ol
as an internal standard. The detection limit of linalool is 1.0 mg/kg, and
the limit of quantification is 3.5 mg/kg. Good agreement was achieved
between the results of the new and steam-distillation methods. In addition,
59 samples of hops from four important Czech varieties (Agnus,
Premiant, Saaz, and Sládek) from the 2013 harvest were analyzed, and
the content of linalool was correlated with the content of bitter acids in
xyz 3-D projection; four separate and clearly limited clusters that corresponded
to the four tested varieties were obtained.
The increasing incidence of Multi Drug Resistance Tuberculosis (MDR-TB) and Extensively Drug Resistance TB (XDR-TB) worldwide highlight the urgent need to search for newer anti-tuberculosis compounds. It has been determined that pharmaceutical plant, hops (Humulus lupulus), possesses some antibacterial effect. In this study, the antimycobacterial effect of this plant on rifampin sensitive and resistant strains of Mycobacterium tuberculosis were examined. Sensitivity and resistance of 37 Iranian isolates of M. tuberculosis to rifampin was determined by proportion method. Ethanolic extract of hops was prepared using maceration method. PCR-SSCP and direct sequencing were used for confirming existence of mutations in 193-bp rpoB amplicons related to the rifampin resistance in Mycobacterium tuberculosis isolates. Two different concentrations of hops alcoholic extract (4 and 8 mg/ml) were prepared and its effects against 21 resistant and 15 sensitive isolates was determinate using proportion method. Six different mutations in the 193-bp amplified rpoB gene fragments and seven distinguishable PCR-SSCP patterns in 21 Iranian rifampin resistant isolates were recognized. This study showed that the percentage of resistance and the type of mutations were correlated with the PCR-SSCP patterns and the type of mutations in rpoB gene (P<0.05). The results of hops antimycobacterial effect showed that different concentrations of hops ethanolic extract (4 and 8 mg/ml) had a remarkable inhibitory effect on rifampin sensitive and resistant isolates of Mycobacterium tuberculosis. Identification of the effective fraction of hops against Mycobacterium tuberculosis is a further step to be studied.
During the beer brewing process, bitter tasting cis and trans iso-α-acids are generated from the precursor α-acids found in hops. The absolute configurations of the α-acid (-)-humulone and several of its derivatives have now been elucidated by X-ray crystallography, thus resolving decades of confusion over the humulone isomerization mechanism.
The antimicrobial activity of hop resins against Streptococcus salivarius, Staphylococcus aureus (two strains), Bacillus megaterium, Escherichia coli B, and Bacillus subtilis was investigated. However, resistance development was carried out on Streptococcus salivarius, Staphylococcus aureus (two strains), and Bacillus megaterium. The two hop resins used were iso-alpha resin and beta resin. Prior to resistance development, S. salivarius, S. aureus, and B. megaterium were all inhibited by the iso-alpha-hop resin in the 0.01 to 0.03% range. The beta-hop resin which, according to the literature, is more active than the iso-alpha resin initially inhibited these organisms at the 0.003 to 0.01% concentrations. The ease of resistance development varied between the different microbes, B. megaterium being the least prone to develop resistance.
To study the relationships and genetic diversity among wild hops, Humulus lupulus, we analyzed 133 samples of wild hops collected from Europe, Asia and North America using polymorphism on 11 microsatellite
loci. Although only three primers showed bands in Japanese hops, all other samples showed polymorphic bands at most loci.
There were no duplicate genotypes among samples of European, Chinese and North American hops, and each individual hop could
be distinguished completely. The phylogenetic tree constructed from DA distance with the UPGMA method showed a large cluster
comprised of European hops, although Russian hops from the Caucasus and Altai regions were separate from the European cluster.
Chinese and North American samples gave distinct clusters suggesting genetic differentiation. This study has indicated that
hop microsatellite DNA is differentiated, and is dependent upon the origin in regions of Europe, Asia and North America.
The antibacterial effect of weak acids derived from the hop plant (Humulus lupulus L.) increased with decreasing pH. Analysis of the minimum inhibitory concentration of such compounds against Lactobacillus brevis IFO 3960 over pH 4-7 suggests that undissociated molecules were mainly responsible for inhibition of bacterial growth. The antibacterial activity of trans-isohumulone was ca 20 times greater than that of humulone, 11 times greater than that of colupulone and nine times greater than that of trans-humulinic acid when the degree of ionization was taken into account. Monovalent cations (K+, Na+, NH4+, Rb+, Li+) stimulated antibacterial activity of trans-isohumulone but the effect was smaller than that observed with H+. The response to divalent cations varied: Ca2+ had little effect on antibacterial activity, whereas Mg2+ reduced activity. Lipid materials and beta-cyclodextrin also antagonized the antibacterial action of trans-isohumulone.
Outline of malting and brewing. Barley. Some aspects of barley grain physiology. The biochemistry of malting grain. Malting conditions and malt types. The technology of malting and kilning. Brewing water. Adjuncts, sugars, wort-syrups and industrial enzymes. The chemistry and biochemistry of mashing. Preparation of the grist. Mashing.
Although female cones of the hop plant (Humulus lupulus) are known primarily as raw material supplying characteristic bitterness and aroma to beer, their equally significant health-promoting effects have been known to mankind for several thousand years and hop is a plant traditionally utilized in folk medicine. This paper summarizes the scientific knowledge on the effects of all 3 major groups of secondary metabolites of hops; polyphenols, essential oils, and resins. Because of their chemical diversity, it is no coincidence that these compounds exhibit a wide range of pharmacologically important properties. In addition to antioxidant, anti-inflammatory, and anticancer-related properties, particular attention is being paid to prenylflavonoids that occur almost exclusively in hops and are considered to be some of the most active phytoestrogens known. Hop oils and resins are well known for their sedative and other neuropharmacological properties, but in addition, these compounds exhibit antibacterial and antifungal effects. Recently, alpha bitter acids have been shown to block the development of a number of complex lifestyle diseases that are referred to by the collective name "metabolic syndrome." Information presented in this review confirms the significant potential for the use of hops in the pharmaceutical industry and provides an understanding of beer as a natural drink that, although moderately consumed, may become a source of many health-promoting compounds.
Of all the herbs that have been used to flavor and preserve beer over the ages, only the hop (Humulus lupulus L.) is now regarded as an essential raw material in brewing throughout the world. Although hops were cultivated in Babylon as far back as 200 A.D., there is no record of their use to make beer until about 1079. The value of hops for flavor and preservation of alcoholic beverages appears to have been recognized by the twelfth century, and, in the thirteenth century, the hop started to threaten traditional herbs, such as rosemary, yarrow, coriander, and bog myrtle. The Bavarian Purity Law of 1516 decreed that only hops could be used for bittering beers in Germany. For a long time, sweet and strong ales were preferred in England, and the hop was condemned as a 'wicked and pernicious weed.' Good sense eventually prevailed, however, and hops were first grown in England in 1524, 100 years before the first gardens were established in North America. Although selection of improved varieties must have been a continuous process for most of the second millennium, the breeding of hops as an organized, scientific operation dates from the start of the twentieth century with a program initiated at Wye College, England, in 1904. In the same year, the α-acid humulone was first isolated as a crystalline solid, and during the next 60 years our knowledge of hop chemistry and understanding of the isomerization process was developed, leading to great benefits for breeders, growers, and brewers alike. Over the last 40 years, there has been a rapid proliferation of types of processed hops, or hop products, which offer the brewer several economic and quality advantages over the use of whole hops, and the contribution of hops to beer aroma, bitterness, foam, and light stability can now be controlled more effectively than ever before.
The flavonoids of hops include flavonol glycosides, condensed tannins, and prenylflavonoids. The first two flavonoid classes are located intracellularly, while the prenylflavonoids are secreted along with bitter acids and essential oils by the lupulin glands of the inflorescences. The chemistry and biological activities of prenylflavonoids isolated from the lupulin fraction are reviewed. An LC-MS method was developed for quantitation of these phenolics in hops, hop-derived products, and beer. The fate of xanthohumol and related prenylflavonoids during the brewing process was investigated by LC-MS. The partial carryover of the prenylflavonoids from hops into beer was attributed mainly to incomplete extraction and adsorption to insoluble proteins and yeast. Moreover, the prenylchalcone-type flavonoids were largely converted into isomeric prenylflavanones during wort boiling. The biological activities of some of the prenylflavonoids isolated were examined using in vitro techniques. Some of the prenylflavonoids inhibited the growth of breast cancer (MCF-7) cells in a dose-dependent manner. Xanthohumol and related prenylflavonoids also inhibited the cytochrome P450-mediated activation of procarcinogens and induced the activity of the carcinogen-detoxifying enzyme, quinone reductase. The prenylflavonoids were not toxic to normal cells (rat hepatocytes) at the same concentrations. Recent literature reports of biological activities are briefly discussed: inhibition of bone resorption, inhibition of diacylglycerol acyltransferase, and antimicrobial activities.
The hop plant (Humulus lupulus, H. americanus etc.) has for centuries been employed to give flavour to fermenting liquors. It is best known as the principal source of the aroma and bitter flavour of beer, and the hops which today are used for this purpose are cultivated plants which have been developed by continuous selection over at least the last century.
In an attempt to alleviate extensive confusion regarding infra-specific variation of Humulus lupulus (s.l.), numerical taxonomic analyses were conducted on 783 herbarium collections of this species. A method combining alternating cycles of principal coordinate analysis and canonical analysis was used to generate morphologically defined groups, the taxonomic acceptability of which was judged on the basis of geographical homogeneity. This technique produced five groups, which are formally recognized here as varieties. Humulus lupulus var. neomexicanus occupies western North America, especially the Cordillera, and is largely allopatric. Humulus lupulus var. pubescens (var. nov.) inhabits the American Midwest. Humulus lupulus var. lupulus occurs in Europe, where it is allopatric, and is introduced elsewhere, especially in eastern North America, where it comprises half of the herbarium plants from this region. Humulus lupulus var. lupuloides (var. nov.) occurs in the eastern part of North America, and intergrades with the other three varieties populating North America, wherever it is sympatric with them. Humulus lupulus var. cordifolius is found in eastern Asia, mainly in Japan. Attempts to cluster these variants hierarchically did not reveal an unambiguous pattern of relationship, although several of the techniques used produced the intuitively satisfying separation of the three North American taxa from the Asian variety and the European variety. Humulus japonicus, a distinctive relative, does not manifest comparable geographical differentiation. Humulus yunnanensis, a Chinese endemic species first described in 1936, has been almost universally unappreciated and identified as H. lupulus, which it resembles superficially. However, it is more similar to H. japonicus. Two contrasting genetic systems are perceivable in the four species comprising the Cannabaceae: Cannabis sativa and H. japonicus seem to have "general purpose genotypes" adapted to cosmopolitan distribution, whereas H. yunnanensis and the varieties of H. lupulus appear to be comparatively specialized for localized habitation.
Humulone, lupulone and related compounds were found to have antifungal activities. The activities of these compounds were tested to determine their structure-activity relationships.As a result, it was found that the six-membered compounds had antifungal activities against Trichophyton spp., whereas, the five-membered compounds were inactive. Among the compounds tested, 3-isopentenylphlorisovalerophenone 12 showed the highest activity, being almost the same as griseofulvin against Trichophyton spp. 12 also had potent activity against Candida, Fusarium, Mucor and Staphylococcus spp. It is suggested that the activity of 12 was significantly affected by the structue of its acyl group.
The hop cones of the female plant of the common hop species Humulus lupulus L. are grown almost exclusively for the brewing industry. Only the cones of the female plants are able to secrete the fine yellow resinous powder (i.e. lupulin glands). It is in these lupulin glands that the main brewing principles of hops, the resins and essential oils, are synthesized and accumulated. Hops are of interest to the brewer since they impart the typical bitter taste and aroma to beer and are responsible for the perceived hop character. In addition to the comfortable bitterness and the refreshing hoppy aroma delivered by hops, the hop acids also contribute to the overall microbial stability of beer. Another benefit of the hop resins is that they help enhance and stabilize beer foam and promote foam lacing. In an attempt to understand these contributions, the very complex nature of the chemical composition of hops is reviewed. First, a general overview of the hop chemistry and nomenclature is presented. Then, the different hop resins found in the lupulin glands of the hop cones are discussed in detail. The major hop bitter acids (- and β-acids) and the latest findings on the absolute configuration of the cis and trans iso--acids are discussed. Special attention is given to the hard resins; the known δ-resin is reviewed and the ε-resin is introduced. Recent data on the bittering potential and the antimicrobial properties of both hard resin fractions are disclosed. Attention is also given to the numerous essential oil constituents as well as their contributions to beer aroma. In addition to the aroma contribution of the well-known essential oil compounds, a number of recently identified sulfur compounds and their impact on beer aroma are reviewed. The hop polyphenols and their potential health benefits are also addressed. Subsequently, the importance of hops in brewing is examined and the contributions of hops to beer quality are explained. Finally, the beer and hop market of the last century, as well as the new trends in brewing, are discussed in detail. Hop research is an ever growing field of central importance to the brewing industry, even in areas that are not traditionally associated with hops and brewing. This article attempts to give a general overview of the different areas of hop research while assessing the latest advances in hop science and their impact on brewing. Copyright © 2014 The Institute of Brewing & Distilling
Analysis of the essential oils from a large number of hop samples, using a combination of gas-liquid partition chromatography and adsorption chromatography, has shown that the oil content is affected by numerous factors including the variety of hop, the conditions during its growth and the treatment received by the cones after picking. Both over-drying and deterioration during storage appear to cause a preferential loss of the more volatile constituents. The total oil can be fractionated into hydrocarbon and oxygenated fractions, and the composition of each fraction would appear to be determined at least in part by varietal factors. It is confirmed that the proportions of myrcene and humulene in the hydrocarbon fraction are related inversely one to the other and can be correlated with the composition of the α-acids and of the β acids present in the hop resins. The biosynthetic implications of these findings are discussed.
Reversed phase high performance liquid chromatography with photodiode array detection allows easy location in hops extract chromatograms of two deoxy-α-acids and in beer extract chromatograms of cohulupone and hulupone.
The composition of essential oil of hops is reviewed and the nature of hop oil components which survive into wort and beer is discussed. Methods which are available to the brewer for imparting hop character to beer are critically evaluated.
Crushed hop seed may be present in hop powders prepared from seeded hops. Microbrewery trials with this material indicate that it will not affect beer quality under normal production brewing conditions.
In order to screen for the bitter compounds generated from hop-derived precursors during the wort boiling process, an ethanolic hop extract was fractionated; the fractions obtained were thermally treated under model wort boiling conditions and, then, sensorially evaluated for their bitterness. Besides the isomerisation of the α-acids into the intensely bitter iso-α-acids, the bitterness of the fraction containing the β-acids was also found to be enhanced after wort boiling. To gain first insights into the β-acid-derived bitter compounds, the β-acid colupulone was isolated, thermally treated under wort boiling conditions and, then, investigated for bitter tasting degradation products by means of a taste dilution analysis (TDA). Besides the cohulupone, five previously unreported bitter-tasting colupulone degradation products, all of which exhibited a lingering, β-acid-like bitter taste with low recognition thresholds between 37.9 and 90.3μmol/l, were isolated and their structures determined as two tricyclocolupone epimers, two dehydrotricyclocolupone epimers, and nortricyclocolupone, respectively, by means of LC–TOF–MS and 1D/2D-NMR spectroscopy.
The composition of essential oil in hops depends mainly on hop variety and less on growing, processing and storage conditions. Therefore the data on the composition can be used to distinguish between hop varieties. During the years 1998–2000, 78 samples of the commonly grown varieties in Slovenia were analyzed by gas chromatography. Research was focused on the selection of suitable components characteristic of the varieties in question. Since the changes in essential oil composition due to ageing are the most important interferences for determination of the varieties, these influences were successfully suppressed using the so-called indexes. Sixteen representative peaks were selected, indexes were calculated and processed by cluster analysis and principal component analysis. The developed method was shown to be effective on all hop varieties important in Slovenia and gave excellent results in daily laboratory practice.
Humulone, a bone resorption inhibitor isolated from hop extract, induced apoptosis in the premyocytic leukemia cell line HL-60 between 1 and 100 μg/ml. Our data suggested that there was a correlation between the apoptosis-inducing activity of humulone and its antioxidative activity.
A gas chromatographic method for the quantitative evaluation of 2-methyl-3-butene-2-ol, a sedative hop constituent, is described. Depending on the storing time, the content of this compound was determined in a large number of hops, hop extracts, and drugs.
While only traces of the compounds were detected in fresh hops, the concentration continously increased after drying to reach maximum levels (approx. 0.15%) within 2 years of storing at room temperature, irrespective of the specific kind. Hop extracts standardized to alpha-acids, which are available on the market, were found to contain relatively small amounts of 2-methyl-3-butene-2-ol.
Only traces of the compounds were discovered in hop containing “sedative dragees”, whereas a relatively high concentration was found in a sedative bath preparation. Thus, pharmacologically relevant concentrations of 2-methyl-3-butene-2-ol can be reached in both tea and bath preparations. However, since there is a reason to suppose that 2-methyl-3-butene-2-ol may also be formed in vivo by metabolization of alpha-acids, negative conclusions as to the effectiveness of the dragees should not be drawn before completion of the current studies.
Bei der Lagerung von Hopfen bildet sich aus Bittersäuren das sedativ-hypnotisch wirksame 2-Methyl-3-buten-2-ol. Der Mechanismus dieser Reaktion, die nur bei Gegenwart von Luftsauerstoff eintritt, wird untersucht und an einem Versuchsmodell gezeigt, daß die Oxidation durch OH-Radikale induziert wird. Überschüssiges OH• kann 2-Methyl-3-buten-2-ol zu Aceton umsetzen, was das Auftreten hoher Aceton-Konzentrationen in altem Lagerhopfen erklärt. Im Gegensatz zu OH• sind weder Peressigsäure noch H2O2 in der Lage Bittersäuren zu 2-Methyl-3-buten-2-ol abzubauen. Die Konsequenzen, die sich aus der Reaktion von Bittersäuren mit Sauerstoffradikal-Spezies für biologische Prozesse in Pflanze, Droge und Säugetierorganismus ergeben, werden diskutiert.
Detection of Sedative-Hypnotic Hop Constituents, V: Degradation of Humulones and Lupulones to 2-Methyl-3-buten-2-ol, a Hop Constituent Possessing Sedative-Hypnotic Activity
In stored hops, 2-methyl-3-buten-2-ol, a hop constituent with sedative-hypnotic activity, is formed from humulones and lupulones. This reaction occurs only in the presence of atmospheric oxygen. In an experimental model, OH radicals were shown to be responsible for the reaction. Excessive OH radicals convert 2-methyl-3-buten-2-ol to acetone. This explains the fact that high acetone concentrations may be found in stored hops. Neither peracetic acid nor H2O2 are capable of degrading humulones and lupulones to 2-methyl-3-buten-2-ol. The importance of the reaction for biological processes in the plant and in mammalian organisms is discussed.
Twenty-six hop bitter resins, some hitherto not investigated, were tested for antimicrobial activities. Gram-positive bacteria were much more sensitive than Gram-negative ones. The inhibitory effect against Bacillus subtilis 168 was measured by several methods and the general rule could be established that the antibiotic properties are mainly dependent on the hydrophobic parts of the molecules. Thus the acyl-lupuphenones (2-acyl-3, 5-4, 4′, 6-tri(3-methyl-2-butenyl)-cyclohexane-triones (1, 3, 5)) having three prenyl and one acyl side chain are the most active substances. Their minimum inhibitory concentration (MIC) increases from the capro (0.5 μM) to the aceto derivative (11 μM). Any substitution with hydrophilic functions or loss of hydrophobic groups causes reductions in biological activity. This is most evident with the corresponding acyl-phloroglucine precursors (2-acyl-1, 3, 5-trihydroxybenzenes) which lack the three prenyl side chains (MIC, 110 to 5050 μM respectively). Conversion of the central six-membered ring structure into a five-membered one results in additional losses of antimicrobial activity. These findings support the proposal that the lipophilic region of the cell membrane represents the target site for the hop bitter resins.
European, Japanese, and North American hop cultivars were compared with each other and with wild plants by means of numerical taxonomic analyses of vegetative morphological characters. The cultivars originating from the three geographical areas tended to be distinguishable. European cultivars proved to be very similar to indigenous wild European Humulus lupulus and almost certainly are derived from the wild plants. Japanese cultivars seem to be imported European stocks which have been introgressed by indigenous wild Japanese H. lupulus. Similarly American cultivars appear to be of hybrid origin, apparently between European cultivars and one of the three major indigenous varieties of wild North American plants. All domesticates examined were notably dissimilar to the midwestern United States H. lupulus var. pubescens, suggesting that this taxon is a potential source of new breeding germ plasm.
Capillary gas chromatography patterns and tables of percentage composition are given for hop oils from the American grown hop varieties Cluster (early, late, seeded, seedless); Fuggle (seeded, seedless); Bullion (seeded and seedless); Brewers Gold (seeded, seedless), and Talisman (seedless). A scheme is described whereby each variety can be readily distinguished from the others by its capillary gas chromatography pattern and by the relative percentages of certain components.
The essential oil of several varieties of hops displayed good varietal uniformity of composition under the following environmental conditions: annual climatic conditions, climates and soils of widely different growing areas within the United States, abnormal ranges of nitrogen and phosphorus fertility over various moisture levels, development of the plant over a 4-year period (hops are perennial), maturity of the crop over a 21-day harvest period, while hosting any of several viruses, through processing, and during storage. These observations were offered as justification for accepting hop oil composition as a reliable criterion for a system of varietal identification.
The essential oils as well as solvent extracts of 11 hop cultivars, 1 hop variety and a wild type of hop were screened for their antimicrobial activities using the agar overlay technique. The oils were isolated from the cones of the various hop plants by hydrodistillation, the extracts were obtained by soaking the hop cones in chloroform. The oils and the extracts showed activity against the Gram-positive bacteria (Bacillus subtilis andStaphylococcus aureus) and the fungus (Trichophyton mentagrophytes var.interdigitale), but almost no activity against the Gram-negative bacterium (Escherichia coli) and the yeast (Candida albicans) used in the screening. The peak area percentages of the main volatile components and the contents of the bitter acids of the extracts were determined for all cultivars using chromatographic methods.
Humulus lupulus (hops) bitter acids, which are well known for their antimicrobial property against Gram-positive bacteria
have negligible activity against Gram-negative bacteria. The hop acids are, however, antiprotozoal. Ciliated protozoa were
more sensitive to hop acids than amoebae. Plasmodia were also sensitive but at a lower level than to the synthetic anti malarial
drugs. Beta resin, tetra iso alpha acid and xanthohumol were studied and the latter was found to be particularly potent against
the protozoa. Carbon dioxide enhanced the protozoicidal effect of hop acids. New data were also presented on specific antifungal
activities. In agreement with the literature hop had very little antifungal property, however a slight coaction was seen between
hop and sorbate on R. nigricans. Carbon dioxide had no enhancing effect on the inhibitory activity of hop against fungi as well as E. coli.
Key Words
Hops
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lupulone
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xanthohumol
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antimicrobial spectrum
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protozoa
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malaria
We report the inhibition of the causative agents of dental caries, Streptococcus mutans and other oral streptococci, by the
antimicrobially active ingredients of the hop plant (Humulus lupulus L.). The hop constituents studied were purified beta acid, xanthohumol, isoalpha acid and tetra iso-alpha acid. Cruder hop
extracts were also investigated. The antimicrobial activity of these hop constituents was tested against four strainsof Streptococcus mutans as well as one strain each ofStreptococcus sanguis andStreptococcus salivarius and compared to antimicrobial essential oils used in mouthwashes in two independent assay systems. We found that all tested
hop constituents inhibited the Streptococci. The minimum inhibitory concentration at pH 7.5 ranged from 2 to 50 μg/ml depending
on the microorganism and hop phytochemical tested. Contrary to a previous report, there was no activity enhancement by ascorbic
acid over and above the enhancement due to pH lowering. Thére was no resistance development to beta acid after 10 passages
in a subinhibitory concentration of this acid. Antimicrobial activity of hop constituents was found to be greater than other
plant products such as thymol, nerol, cinnamon oil, oil of clove, menthol and eucalyptol. The possibilities of using hop constituents
in mouthwashes are discussed.
Five flavonoids were isolated from the resin part of the female inflorescences of Humulus lupulus, together with four known hop flavonoids, i.e. xanthohumol, 2′,4′,6′,4-tetrahydroxy-3′-C-prenylchalcone, iso-xanthohumol and 6-prenylnaringenin. The new hop compounds were identified as 2′,4′,6′,4-tetrahydroxy-3′-C-geranylchalcone, 5′-prenylxanthohumol, 6″,6″-dimethylpyrano (2″,3″: 3′,4′)-2′,4-dihydroxy-6′-methoxychalcone, its hydrate and 8-prenylnaringenin; apart from 8-prenylnaringenin, these are new flavonoids. Their mass fragmentation patterns were studied by mass spectrometry using atmospheric pressure chemical ionization in combination with collision-activated decomposition. Loss of the isoprenoid substituent in the positive ion mode and retro Diels-Alder fission in both the positive and negative ion modes provided useful information on the substitution patterns of the A and B rings. Nine hop varieties were qualitatively and quantatively characterized by HPLC-mass spectrometry. The flavonoid profiles of the samples examined were uniform and proved to be of little value in hop variety identification. Xanthohumol was the principal flavonoid in all samples (80–90% of the total of flavonoids) and was accompanied by minor amounts of the other eight flavonoids in virtually all samples.
Although the complex taste profile of beer is well accepted to be reflected by the molecular blueprint of its sensometabolites, the knowledge available on the process-induced transformation of hop-derived phytochemicals into key sensometabolites during beer manufacturing is far from comprehensive. The objective of the present investigation was, therefore, to develop and apply a suitable HPLC-MS/MS method for the simultaneous and comprehensive quantitative monitoring of a total of 69 hop-derived sensometabolites in selected intermediary products throughout a full-scale beer manufacturing process. After data normalization, the individual sensometabolites were arranged into different clusters by means of agglomerative hierarchical analysis and visualized using a sensomics heatmap to verify the structure-specific reaction routes proposed for their formation during the beer brewing process.
Thermal treatment of the hop beta-acid colupulone under wort boiling conditions, followed by LC-TOF-MS and 1D/2D NMR spectroscopy, revealed cohulupone, hulupinic acid, nortricyclocolupone, two tricyclocolupone epimers, two dehydrotricyclocolupone epimers, two hydroxytricyclocolupone epimers, and two hydroperoxytricyclocolupone epimers as the major bitter-tasting beta-acid transformation products. Among these compounds, the chemical structures of the hydroxy- as well as the hydroperoxytricyclocolupone epimers have not previously been confirmed by 1D/2D NMR experiments. Depending on their chemical structure, these compounds showed rather low recognition thresholds ranging from 7.9 to 90.3 micromol/L. The lowest thresholds of 7.9 and 14.7 micromol/L were found for cohulupone, imparting a short-lasting, iso-alpha-acid-like bitter impression, and for hydroxytricyclocolupone, exhibiting a long-lasting, lingering, and harsh bitterness perceived on the posterior tongue and throat. Furthermore, HPLC-ESI-MS/MS analysis allowed for the first time a simultaneous detection and quantitation of these bitter-tasting beta-acid transformation products in a range of commercial beer samples without any sample cleanup. Depending on the type of beer, these studies revealed remarkable differences in the concentrations of the individual beta-acid transformation products.
The essential oils as well as solvent extracts of 11 hop cultivars, 1 hop variety and a wild type of hop were screened for their antimicrobial activities using the agar overlay technique. The oils were isolated from the cones of the various hop plants by hydrodistillation, the extracts were obtained by soaking the hop cones in chloroform. The oils and the extracts showed activity against the Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and the fungus (Trichophyton mentagrophytes var. interdigitale), but almost no activity against the Gram-negative bacterium (Escherichia coli) and the yeast (Candida albicans) used in the screening. The peak area percentages of the main volatile components and the contents of the bitter acids of the extracts were determined for all cultivars using chromatographic methods.
Epidemiologic studies have suggested that consumption of phytoestrogen-rich foods may protect against breast cancer, and phytoestrogens such as genistein have been reported to both inhibit and stimulate the growth of some human breast cancer cells. The phytoestrogens genistein, daidzein, biochanin A, and coumestrol were tested and found to inhibit serum-stimulated growth in both T-47D and MCF-7 breast cancer cells at 10-100 microM. Extracts of several estrogenic herbs, including hops, black cohosh and vitex, inhibited growth of T-47D cells. These in vitro results suggest that certain herbs and phytoestrogens may have potential in the prevention of breast cancer.
We investigated whether crude hop extracts and purified hop components representing every major chemical class of hop compound have antiviral activity. These hop constituents were tested for antiviral activity against bovine viral diarrhea virus (BVDV) as a surrogate model of hepatitis C virus (HCV), human immunodeficiency virus (HIV), influenza A virus (FLU-A), influenza B virus (FLU-B), rhinovirus (Rhino), respiratory syncytial virus (RSV), yellow fever virus (YFV), cytomegalovirus (CMV), hepatitis B virus (HBV), and herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2). The extracts all failed to prevent the replication of HIV, FLU-A, FLU-B, RSV and YFV. A xanthohumol-enriched hop extract displayed a weak to moderate antiviral activity against BVDV (therapeutic index (TI)=6.0), HSV-2 (TI=>5.3), Rhino (TI=4.0) and HSV-1 (TI=>1.9) with IC(50) values in the low microg/ml range. Pure iso-alpha-acids demonstrated low to moderate antiviral activity against both BVDV (TI=9.1) and CMV (TI=4.2) with IC(50) values in the low microg/ml range. No antiviral activity was detected using beta-acids or a hop oil extract. Ultra-pure preparations (>99% pure) were used to show that xanthohumol accounted for the antiviral activity observed in the xanthohumol-enriched hop extract against BVDV, HSV-1 and HSV-2. Xanthohumol was found to be a more potent antiviral agent against these viruses than the isomer iso-xanthohumol. With Rhino, the opposite trend was observed with iso-xanthohumol showing superior antiviral activity to that observed with xanthohumol. Xanthohumol also showed antiviral activity against CMV, suggesting that it might have a generalized anti-herpesvirus antiviral activity. Again, superior antiviral activity was observed with the xanthohumol isomer against CMV. In summary, iso-alpha-acids and xanthohumol were shown to have a low-to-moderate antiviral activity against several viruses. These hop constituents might serve as interesting lead compounds from which more active anti-HCV, anti-Rhino and anti-herpesvirus antiviral agents could be synthesized.