Humulus Lupulus Research Articles

Comparative analysis of four hop cultivars grown in Brazil and the USA by GC-MS-based metabolomics

Why was the work done: Although the third largest beer producer in the world, Brazil currently imports the majority of its hops. A recent development is the cultivation of hops (Humulus lupulus L.) in Brazil. In addition to genetic factors, the chemical composition of hops can exhibit variations due to conditions of cultivation. Accordingly, it is of value to characterise and differentiate hop cultivars grown in Brazil with the same cultivars grown in a long established location such as the United States of America. How was the work done: Centennial, Chinook, Columbus, and Nugget cultivars grown in Brazil or in the USA were compared by metabolomic analyses of the chemical profiles using gas chromatography coupled to mass spectrometry. Principal component analysis showed sample grouping according to where the hops were grown. Partial Least Squares Discriminant Analysis allowed the characterisation of the main metabolites that discriminated hop samples from the two countries. A total of 31 metabolites were putatively identified, including monoterpenes, sesquiterpenes, oxygenated mono- and sesquiterpenes, esters, alcohols, and ketones. What are the main findings: There were clear metabolic differences between the same hop varieties grown in Brazil or the USA. The metabolites with the greatest discriminating power for Brazilian hops were trans-α-bergamotene, 2-decanone, and ι-gurjunene, while American hops presented β-copaene, humuladienone, and isopentyl isobutyrate. Notably, trans-α-bergamotene was present in Brazilian hops but absent from American hops. Why is the work important: This study sheds light on the differences in the chemical composition of hops cultivated in Brazil compared those cultivated in the USA. This knowledge may stimulate new producers and contribute to the development of hop cultivation in Brazil.

Sleep-enhancing effect of Hongcheon-hop (Humulus lupulus L.) extract containing xanthohumol and humulone through GABAA receptor

Ethnopharmacological relevanceThe bitter resins in hops (Humulus lupulus) modulate GABA receptors, leading to central nervous system suppression, which induces sedative effects and enhances sleep. Aim of the studyThis study intends to explore the sleep-enhancing properties of Hongcheon-hop extract, a hop native to Korea, by analyzing sleep structure and its mechanisms through EEG. Materials and methodsA pentobarbital-induced sleep model was used, along with EEG analysis to study sleep architecture. The receptor binding of Hongcheon-hop extract was analyzed using GABA receptor antagonists. ResultsThe extract contained 7.44 mg/g of xanthohumol, 133.04 mg/g of α-acids including 13.74 mg/g of humulone and 84.52 mg/g of β-acids. Administration of the extracts resulted in a dose-dependent enhancement of sleep duration. Both low (100 mg/kg) and high doses (200 mg/kg) of the extract increased non-rapid eye movement (NREM) sleep by enhancing δ wave sleep, which represents deep sleep. The extract exerted its sleep-promoting effects by binding to the γ-aminobutyric acid (GABA) binding site on GABAA receptor. In an insomnia model, low dose of the extract was more effective than the same dose of GABA in enhancing sleep. Administration of the extract for 3 weeks increased the expression and protein levels of 5-HT1A receptors in addition to GABAA receptor, and also increased the content of GABA in the brain. A mixture of xanthohumol (1.49 mg) and humulone (2.75 mg) within Hongcheon-hop extract (200 mg) exhibited a sleep-enhancing effect comparable to that of the extract. ConclusionThese findings suggest that Hongcheon-hop extract, which contains xanthohumol and humulone, improves sleep quality by increasing NREM sleep through the enhancement of δ-wave sleep via GABAA receptors. Hongcheon-hop shows potential as a natural therapeutic agent for treating insomnia and enhancing sleep.

Investigation of the Use of Hops (Humulus lupulus) and Calendula (Calendula officinalis) As Disinfectants on the Hatching Efficiency of Rainbow Trout (Oncorhynchus mykiss)

This study investigates the potential application of plant-based resources with antimicrobial properties, namely hops (Humulus lupulus) and calendula (Calendula officinalis), as viable alternatives to commercial disinfectants for the prevention of fungal growth during the incubation period of rainbow trout (Oncorhynchus mykiss) eggs. Fertilized eggs were examined with daily 20-minute baths in 0.25 mg, 0.5 mg, and 1 mg concentrations throughout the incubation period (33-35 days). Control group, commercial formaldehyde, hops, and calendula groups were examined in triplicate for each concentration. As a result, the lowest hatching ratio was observed in the control group with 84.77%, while the hatching ratios in the other groups were as follows: commercial disinfectant group with 86.22%, hops group with 87.44% (0.25 mg), calendula group 88% with (0.25 mg), calendula group with 89% (0.5 mg), calendula group with 89.33% (1 mg), hops group with 89.55% (0.5 mg), and the highest hatching ratio was found in the hops group with 90.66% (1 mg). The lowest survival rate was observed in the control group with 85.22%, with the survival rates of the other groups were 86.44% in the commercial disinfectant group, 87.55% (0.25 mg) in the hops group, 88.55% (0.25 mg) in the calendula group, 88.88% (0.5 mg) in the calendula group, 89.33% (1 mg) in the calendula group, 89.55% (0.5 mg) in the hops group, and the highest survival rate was 90.11% (1 mg) in the hops group. In conclusion, it was specified that plant-based by-products (hops and calendula) could be used as alternative disinfectants to commercial chemicals in the disinfection of rainbow trout eggs and fry, and the most appropriate concentration was 1 mg.

Optimization of trellis design and height for double-season hop (Humulus lupulus L.) production in a subtropical climate: Growth, morphology, yield, and cone quality during establishment years

Photoperiod manipulation using supplemental lighting enables double-season production of hops (Humulus lupulus L.) under subtropical climatic conditions. In Florida, United States, the spring growing season (Spring) is from February to June, and the fall growing season (Fall) is from June to November. To develop the optimum trellis for this unique hop production system, we examined the effects of two trellis designs (straight trellis and V-trellis) and three trellis heights (3.7, 4.6, and 5.5 m) on growth, morphology, yield, and cone quality of 'Cascade' hops grown in west central Florida. The straight trellis had two twines per hill installed on a top middle cable, whereas the V-trellis had four twines per hill installed on two top parallel cables. We trained 16 bines per hill for both trellises. Data were collected during establishment years: Year 1 and Year 2. Yield showed significant season × trellis height interaction effects. Surprisingly, yield was highest in Year 1 Spring and decreased by 45–74 % in the subsequent seasons. Increasing trellis height from 3.7 to 5.5 m increased yield by 78–215 %. On average, the V-trellis produced 24 % higher yield than the straight trellis. The 5.5-m V-trellis produced the highest annual yield of 1807 kg ha–1 in Year 1. Yield had a significant positive correlation with stem dry weight in Year 1 Spring and Year 2 Spring, but it had no significant correlation with bine number per hill, stem diameter, and internode length in any season. Cone quality showed significant seasonal variations. Total α acid concentration decreased from Spring to Fall in both years and recorded the highest value in Year 2 Spring. Similarly, total essential oil content was highest in Year 2 Spring. Except in Year 2 Fall, total α acid concentration (5.35–8.25 %) was within or above the normal range for ‘Cascade’. Compared to these seasonal variations, trellis design and height effects on cone quality were relatively small. These results suggest that, during establishment years, adopting a V-trellis design and increasing trellis height can maximize yield in subtropical hop production without compromising overall cone quality. Ongoing research will validate these findings in mature hop plants.

Allergenic Potential of Common Hops (Humulus lupulus L.) in the Context of Cross-Reactions with Pollen Allergens.

Common hops (Humulus lupulus L.) play a key role in brewing, providing the bitterness, flavor, and aroma of beer, and are widely used in supplements for their antibacterial, anti-inflammatory, and antioxidant properties. However, despite their broad applications, the allergenic potential of common hops remains underexplored, particularly when compared to the closely related Humulus japonicus. This preliminary study aimed to investigate the allergenic potential of common hops and their potential cross-reactivity with common pollen allergens. The immunoreactivity of hop stalks, leaves, and cones was assessed using antibodies against major allergens from birch (Bet v1a), mugwort (Art v1), and timothy grass (Phl p5b), as well as three sera from pollen-allergic patients. Slot Blot analysis was performed using phosphate-buffered saline extracts from the stalks, leaves, and cones of three hop cultivars, while Western Blotting followed SDS-PAGE protein separation. The results revealed significant immunoreactivity in native hop proteins, with diminished reactivity observed in denatured proteins. Cross-reactivity between hop proteins and major pollen allergens was confirmed, indicating that hop proteins may contribute to allergic sensitization in pollen-sensitive individuals. These findings underscore the potential allergenic risks associated with the consumption or exposure to hop-containing products.

Synergistic Proliferation Effects of Xanthohumol and Niflumic Acid on Merkel and Glioblastoma Cancer Cells: Role of Cell Membrane Interactions

The objective of our research was to determine the effects of xanthohumol (XN), a flavonoid isolated from hops (Humulus lupulus), and the anti-inflammatory drug niflumic acid (NA), separately and in combination with each other, on the proliferation of human cancer cells. Additionally, so as to understand the mechanism underlying the anticancer properties of the tested compounds, their effects on the biophysical parameters of a model membrane were assessed. The cells were incubated with XN and NA at various concentrations, either individually or in combination with each other. Cell proliferation was quantified using the sulforodamine B (SRB) assay. In addition, the IC50 values for niflumic acid and xanthohumol applied separately were determined by cell proliferation tests for the following human cancer cell lines: 5637 (urinary bladder carcinoma), A-431 (epidermoid carcinoma), UM-SCC-17A (head and neck squamous carcinoma), SK-MEL-3 (melanoma), MCC13 (Merkel cell cancer), and A172 (glioblastoma), in comparison with the mouse normal fibroblasts (BALB/3T3 clone A31). The results show that the two-compound combinations of XN and NA significantly decreased the proliferation of cancer cells in a dose-dependent manner, and the effects were stronger than the additive responses to XN and NA individually. The membrane studies revealed a synergistic effect on the membrane rigidity when using the mixture of XN and NA, which may explain the observed increase in anticancer activity for the combined XN and NA. Our results suggest that NSAIDs, such as niflumic acid, may be a promising strategy for co-application with xanthohumol as anticancer drugs.

Humulus lupulus L.: Evaluation of Phytochemical Profile and Activation of Bitter Taste Receptors to Regulate Appetite and Satiety in Intestinal Secretin Tumor Cell Line (STC-1 Cells).

Inflorescences of the female hop plant (Humulus lupulus L.) contain biologically active compounds, most of which have a bitter taste. Given the rising global obesity rates, there is much increasing interest in bitter taste receptors (TAS2Rs). Intestinal TAS2Rs can have beneficial effects on obesity when activated by bitter agonists. This study aims to investigate the mechanism of action of a hydroalcoholic hop extract in promoting hormone secretion that reduces the sense of hunger at the intestinal level through the interaction with TAS2Rs. The results demonstrate that the hop extract is a rich source of bitter compounds (mainly α-, β-acids) that stimulate the secretion of anorexigenic peptides (glucagon-like peptide 1 [GLP-1], cholecystokinin [CCK]) in a calcium-dependent manner while reducing levels of hunger-related hormones like ghrelin. This effect is mediated through interaction with TAS2Rs, particularly Tas2r138 and Tas2r120, and through the activation of downstream signaling cascades. Knockdown of these receptors using siRNA transfection and inhibition of Trpm5, Plcβ-2, and other calcium channels significantly reduces the hop-induced calcium response as well as GLP-1 and CCK secretion. This study provides a potential application of H. lupulus extract for the formulation of food supplements with satiating activity capable of preventing or combating obesity.

IDENTIFICAÇÃO E QUANTIFICAÇÃO DOS TEORES DE α E β-ÁCIDOS DOS LÚPULOS PLANTADOS NO ESPÍRITO SANTO POR CROMATOGRAFIA LÍQUIDA DE ALTA EFICIÊNCIA (HPLC)

Brazil is the third largest beer producer in the world, behind only to China and the United States. However, one of the essential raw materials to produce the drink, hops (Humulus Lupulus L.), still faces significant dependence on imports. Inside the lupulin glands located in female hop flowers are compounds that provide bitterness, aroma and important biological activities. It is the molecules known as α and β-acids (Humulones and Lupulones), together with their essential oils that contribute to this. The quantification of these α and β-acids is vital for brewers and researchers, since they improve the sensorial and functional characteristics of beers. In the last decade, through the certification of seedlings of this flower in Brazil, some Brazilian states have been presenting varieties well adapted to the climate. The states of the South and Southeast, at the forefront of this cultivation, have been playing a crucial role in this process of popularizing Hops. Thus, the objective of this work was the quantification, by High Performance Liquid Chromatography (HPLC), of the α and β-acids present in samples from Espírito Santo and other states in the country. The results indicated a high amount of β-acids in the Teamaker variety (12.51 g 100 g-1, m/m), while α-acids were predominant in varieties such as Zeus (14.89 g 100 g-1, m/m) and Comet (14.69 g 100 g-1, m/m). The study also demonstrated that the flower processing stage (harvesting, drying and storage) still requires greater care, since some varieties studied (Polaris and East Rent Golding) present a significant amount of compounds already oxidized due to poor conservation.

Hop as a phytogenic alternative to antibiotic growth promoters in poultry production.

With the rapid growth of the world's population, the demand for food is also increasing. Poultry accounts for 40% of the global meat sector and therefore represents a significant area for further growth. One starting point for increasing production is to refine the composition of feed to improve the efficiency of growth and nutrient utilization, prevent disease and at the same time reduce environmental impact. Similar considerations have led to the long-standing sub-therapeutic use of antibiotics as growth promoters in animal husbandry, which is associated with the threat of rising antimicrobial resistances and the resulting consequences for human and animal health. In order to circumvent these drawbacks, an increasing number of alternative feed additives are becoming more prevalent. The use of phytogenic feed additives, which includes hops (Humulus lupulus), is regarded as a viable alternative. In addition to its natural availability, hops have been demonstrated to exhibit antimicrobial effects and there is increasing evidence of growth-promoting effects in vivo. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Application of Response Surface Methodology to Design and Optimize Purification of Acetone or Aqueous Acetone Extracts of Hop Cones (Humulus lupulus L.) Using Superparamagnetic Iron Oxide Nanoparticles for Xanthohumol Isolation.

Iron oxide nanoparticles (IONPs) are an ideal sorbent for magnetic dispersion extraction due to their superparamagnetic properties and developed and active surface. This work aims to use IONPs, obtained by chemical co-precipitation, to purify 100% acetone and 50% acetone extracts from hop cones (Humulus lupulus L.) obtained by ultrasonic-assisted solvent extraction. The extracts were purified from bitter acids (i.e., humulones, lupulones) to isolate xanthohumol. The sorption conditions were optimized depending on the composition of the extraction mixture, specifically the mass of IONPs and the time needed to achieve effective sorption using response surface methodology (RSM). An analysis of variance (ANOVA) was performed to assess the adequacy of the developed model, and a good agreement was found between the experimental data and the proposed model. The polynomial equation describing the model is highly significant (p < 0.05), with a precision of Adeq (above 4). This indicates the usefulness of the polynomial regression model for prediction in experimental design. The final products of the purification for 100% acetone extracts and 50% acetone contain 40.58 ± 2.84 µg mL-1 and 57.64 ± 0.83 µg mL-1 of xanthohumol, respectively. The use of 50% acetone extract provides more favorable conditions due to the smaller amount of nanoparticles required for extract purification and a higher recovery of xanthohumol. The development of a reliable multivariate model allowed for the optimization of the extract purification process, resulting in high-purity xanthohumol from natural sources.

Biotransformation of Xanthohumol by Entomopathogenic Filamentous Fungi.

Xanthohumol (1) is a major prenylated flavonoid in hops (Humulus lupulus L.) which exhibits a broad spectrum of health-promoting and therapeutic activities, including anti-inflammatory, antioxidant, antimicrobial, and anticancer effects. However, due to its lipophilic nature, it is poorly soluble in water and barely absorbed from the gastrointestinal tract, which greatly limits its therapeutic potential. One method of increasing the solubility of active compounds is their conjugation to polar molecules, such as sugars. Sugar moiety introduced into the flavonoid molecule significantly increases polarity, which results in better water solubility and often leads to greater bioavailability. Entomopathogenic fungi are well known for their ability to catalyze O-glycosylation reactions. Therefore, we investigated the ability of selected entomopathogenic filamentous fungi to biotransform xanthohumol (1). As a result of the experiments, one aglycone (2) and five glycosides (3-7) were obtained. The obtained (2″E)-4″-hydroxyxanthohumol 4'-O-β-D-(4‴-O-methyl)-glucopyranoside (5) has never been described in the literature so far. Interestingly, in addition to the expected glycosylation reactions, the tested fungi also catalyzed chalcone-flavanone cyclization reactions, which demonstrates chalcone isomerase-like activity, an enzyme typically found in plants. All these findings undoubtedly indicate that entomopathogenic filamentous fungi are still an underexploited pool of novel enzymes.

Hops across Continents: Exploring How Terroir Transforms the Aromatic Profiles of Five Hop (Humulus lupulus) Varieties Grown in Their Countries of Origin and in Brazil

Humulus lupulus, or hops, is a vital ingredient in brewing, contributing bitterness, flavor, and aroma. The female plants produce strobiles rich in essential oils and acids, along with bioactive compounds like polyphenols, humulene, and myrcene, which offer health benefits. This study examined the aromatic profiles of five hop varieties grown in Brazil versus their countries of origin. Fifty grams of pelletized hops from each strain were collected and analyzed using HS-SPME/GC-MS to identify volatile compounds, followed by statistical analysis with PLS-DA and ANOVA. The study identified 330 volatile compounds and found significant aromatic differences among hops from different regions. For instance, H. Mittelfrüher grown in Brazil has a fruity and herbaceous profile, while the German-grown variety is more herbal and spicy. Similar variations were noted in the Magnum, Nugget, Saaz, and Sorachi Ace varieties. The findings underscore the impact of terroir on hop aromatic profiles, with Brazilian-grown hops displaying distinct profiles compared to their counterparts from their countries of origin, including variations in aromatic notes and α-acid content.

Exploring antioxidative properties of xanthohumol and isoxanthohumol: An integrated experimental and computational approach with isoxanthohumol pKa determination

This study explores the antioxidative activities of xanthohumol (XN) and isoxanthohumol (IXN), prenylated flavonoids from Humulus lupulus (family Cannabaceae), utilizing the oxygen radical absorption capacity (ORAC) and ferric reducing antioxidant power (FRAP) assays along with computational Density Functional Theory methods. Experimentally, XN demonstrated significantly higher antioxidative capacities than IXN. Moreover, we determined IXN pKa values using the UV/Vis spectrophotometric method for the first time, facilitating its accurate computational modeling under physiological conditions. Through a thermodynamic approach, XN was found to efficiently scavenge HOO• and CH3O• radicals via Hydrogen Atom Transfer (HAT) and Radical Adduct Formation (RAF) mechanisms, while CH3OO• scavenging was feasible only through the HAT pathway. IXN exhibited its best antioxidative activity against CH3O• via both HAT and RAF mechanisms and could also scavenge HOO• through RAF. Both Single Electron Transfer (SET) and Sequential Proton Loss-Electron Transfer (SPLET) mechanisms were thermodynamically unfavorable for all radicals and both compounds.

Phytochemical, spectroscopic analysis and antifungal activity on bell peppers of hydrothermal bioactive metabolites of Humulus lupulus L. extracts

This study aimed to evaluate the impact of temperature on the potential extraction of bioactive compounds from aqueous hop extract samples. The main bioactive components were characterised and analysed by LC-MS/MS, FT-IR, phenolic compounds and total flavonoids. Antifungal activity was evaluated in vitro and in vivo in bell peppers. LC-MS/MS analysis demonstrated increases and decreases of bioactive compounds in both extracts depending on the extraction temperature of 25 or 65 °C. The bioactive compounds showed significant changes in the bands between 2786 to 3600 cm−1 and 1022 to 1729 cm−1 in the FT-IR spectrum. The highest antifungal activity against the microorganisms was observed in the EkuanotMT extract at an extraction temperature of 65 °C. The in vivo test with bell peppers presented antifungal activity during five days of evaluation under normal environmental conditions without refrigeration, presenting ≤ 52% of the disease due to F. oxysporum and A. solani.

Seed pretreatment using design of engineering approach for regulating &lt;em&gt;Humulus lupulus&lt;/em&gt; seed germination in different media

Humulus lupulus, a plant of commercial benefit, has been widely explored for its therapeutic applications. Plant propagation via seeds is one of the major challenges due to seed dormancy and low germination. The physical dormancy of the seed caused by a hard seed coat makes seeds impervious to water. Different types of methods have been reported to break the seed dormancy. The present study emphasizes the optimized chemical method of seed pretreatment for regulating the germination efficiency in three different media namely, Murashige and Skoog (MS), Hoagland’s media and Leafy 200®. The study explores the interaction between two variables viz., acid treatment time and concentration of sulphuric acid, on germination of Humulus lupulus seeds using the Design of Experiment (DOE) approach. The results showed a higher germination rate in MS media and Leafy200® media (100%) seed germination percentage with respect to Hoagland’s media. The result demonstrates the synergistic role of seed pretreatment and media on the seed germination efficiency. The scanning electron microscopy (SEM) analysis of the seeds pretreated with acid revealed small perforations on the seed coat ranging between 5-15 µm. Furthermore, the elemental analysis of the seed coat surface by Energy Dispersive X-ray (EDX) revealed a substantial decrease in carbon and oxygen (%) and the presence of calcium, magnesium, and sulfur. The results indicate the acid hydrolysis of organic constituents on the seed surface enabling changes in seed porosity. Additionally, factors such as pretreatment and media play a pivotal role in regulating seed germination.

First report of Diaporthe humulicola causing halo blight of hop (Humulus lupulus L.) in Prince Edward Island, Canada

This study documents the first report of halo blight of hop (Humulus lupulus L.), caused by the fungal pathogen Diaporthe humulicola, in Prince Edward Island (PE), Canada. This pathogen has been previously reported in Michigan, New York, Connecticut and Quebec. Disease symptoms were reported in hopyards in Harrington and Mount Albion, PE. Symptoms reported include both foliar lesions and severe necrosis of hop cones. Through a metagenomic approach using Nanopore sequencing of the full Internal Transcribed Spacer (ITS) region products, multiple fungal species were identified in infected hop cones. Many plant pathogens were present in the hop cones including species of Botrytis, Alternaria, Colletotrichum and Fusarium. Additionally, metagenomic sequencing identified reads that most closely matched D. humulicola. Symptomatic leaf tissue sections were cultured on amended PDA to isolate the pathogen, then colony PCR was conducted and ITS regions were sequenced, confirming the identity of D. humulicola. Pathogenicity was validated using Koch’s postulates on hop leaf disks, with lesion development occurring 7 days post-inoculation. Considering the humid conditions characteristic of eastern North American hop-growing zones, halo blight’s emergence in PE emphasizes the need for comprehensive monitoring and improved best management strategies to protect the PE hop industry.

Detection and molecular characterization of a novel mitovirus associated with Passiflora edulis Sims.

Mitoviruses are cryptic capsidless viruses belonging to the family Mitoviridae that replicate and are maintained in the mitochondria of fungi. Complete mitovirus-like sequences were recently assembled from plant transcriptome data and plant leaf tissue samples. Passion fruit (Passiflora spp.) is an economically important crop for numerous tropical and subtropical countries worldwide, and many virus-induced diseases impact its production. From a large-scale genomic study targeting viruses infecting Passiflora spp. in Brazil, we detected a de novo-assembled contig with similarity to other plant-associated mitoviruses. The contig is ∼2.6kb long, with a single open reading frame (ORF) encoding an RNA-dependent RNA polymerase (RdRP). This contig has been named "passion fruit mitovirus-like 1" (PfMv1). An alignment of the predicted amino acid sequence of the RdRP of PfMv1 and those of other plant-associated mitoviruses revealed the presence of the six conserved motifs of mitovirus RdRPs. PfMv1 has 79% coverage and 50.14% identity to Humulus lupulus mitovirus 1. Phylogenetic analysis showed that PfMV1 clustered with other plant-associated mitoviruses in the genus Duamitovirus. Using RT-PCR, we detected a PfMv1-derived fragment, but no corresponding DNA was identified, thus excluding the possibility that this is an endogenized viral-like sequence. This is the first evidence of a replicating mitovirus associated with Passiflora edulis, and it should be classified as a member of a new species, for which we propose the name "Duamitovirus passiflorae".

Novel hop ecotypes revealed genetic variation in Chilean Humulus lupulus L.

Novel hop ecotypes revealed genetic variation in Chilean Humulus lupulus L.

Acaricidal properties of Corsican Humulus lupulus L. (Cannabaceae) essential oils against Varroa destructor: a honeybee health perspective

ABSTRACT Six Corsican essential oils (EOs) from Humulus lupulus were studied for their activity against Varroa destructor adults and Apis mellifera pupae. The GC/MS analysis of EOs showed that the major compounds of all accessions were α-Humulene, Myrcene, α-Selinene, β-Selinene, (E)-β-Farnesene, and (E)-β-Caryophyllene. Bioassays showed that EOs from each accession acted as toxins and repellents against V. destructor adults, with lower toxicity towards A. mellifera pupae. In terms of efficacy against V. destructor adults, Smaragd 2020 oil displayed the highest performance, with LC50 and LC90 values of 2.33 and 7.83 µL/L air, respectively. Meanwhile, Smaragd 2019 and Tettnanger EOs showed moderate toxicity, with LC50 values of 3.101 and 3.66 µL/L air, along with LC90 values of 11.67 and 19.89µL/L air, respectively. The oils from Biguglia and Ajaccio were strongly repellent to Varroa adults. At the lowest concentration (2 µL/mL), these EOs exhibited percentage of repellence greater than 70% after 2h exposure, with RC50 values of 1.66 and 1.26 µL/L air, respectively. Concerning their insecticidal effects, EOs demonstrate reduced toxicity towards bee pupae when compared to Varroa mites. Notably, Ajaccio stands out for inducing lower mortality among bee pupae, with a selectivity ratio below 2 and LC50 of 11.25 µL/L air.

Evaluation of variability in alpha and beta acid content in European hop varieties (Humulus lupulus L.)

Between 2009 and 2023, European hop varieties were evaluated within genetic resources in the Czech Republic. The objective of this paper was to determine the variability of hop alpha and beta acid contents in the monitored varieties at a single site over the period of fifteen years. At the same time, the trend in which the observed substances decrease or increase was assessed. The lowest average alpha acid content was detected in Strisselspalter (2.96% w/w), while the highest content was found in Herkules (14.03% w/w). The lowest variability in alpha acid content was measured in Vital (14.59%) and Herkules (16.48%). Unlike the aforementioned varieties, Golding exhibits the highest variability (46.28%). All varieties showed a decreasing trend in alpha acid content over the fifteen years of cultivation. Lubelski had the highest decrease in alpha acid content and also showed a high correlation (r² = 0.664). The varieties with the lowest average beta acid content were Celeia (2.77% w/w) and Golding (2.97% w/w). The variety with the highest average beta acid content was Vital (7.30% w/w). All varieties displaied a decreasing trend in beta acid content. Perle had the lowest trend of decrease in beta acid content, while Tradition had the highest trend of decrease. The varieties Strisselspalter, Saaz, Tettnang, Sládek, and Bobek had an alpha/beta acid ratio below 1. However, the variety Bobek showed the highest variability at 32.18%. Herkules had the highest alpha/beta acid ratio (3.20). The most stable alpha/beta acid ratio was found in Marynka (8.41%).