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Dostálek P, Karabín M, Jelínek L. Hop Phytochemicals and Their Potential Role in Metabolic Syndrome Prevention and Therapy. Molecules 2017; 22:E1761. [PMID: 29048380 PMCID: PMC6151408 DOI: 10.3390/molecules22101761] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/14/2017] [Accepted: 10/17/2017] [Indexed: 01/04/2023] Open
Abstract
Historically, hop cones (Humulus lupulus) have been used since ancient times as a remedy for many ailments and, as a source of polyphenols and bitter acids, is very effective in the treatment of metabolic syndrome (MS). Hop flavonoids, particularly xanthohumol (XN), are substances with hypoglycemic, antihyperlipidemic, and antiobesity activities. Iso-α-acids (IAA) and matured hop bitter acids (MHBA) improve health by influencing lipid metabolism, glucose tolerance, and body weight. The modulatory effect of IAA and MHBA on lipid metabolism may also be responsible for a loss in body weight. These results suggest promising applications for IAA, MHBA, and XN in humans, particularly in the prevention of diet-induced obesity and diabetes.
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Affiliation(s)
- Pavel Dostálek
- Department of Biotechnology, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
| | - Marcel Karabín
- Department of Biotechnology, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
| | - Lukáš Jelínek
- Department of Biotechnology, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
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Ano Y, Dohata A, Taniguchi Y, Hoshi A, Uchida K, Takashima A, Nakayama H. Iso-α-acids, Bitter Components of Beer, Prevent Inflammation and Cognitive Decline Induced in a Mouse Model of Alzheimer's Disease. J Biol Chem 2017; 292:3720-3728. [PMID: 28087694 DOI: 10.1074/jbc.m116.763813] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 01/04/2017] [Indexed: 12/31/2022] Open
Abstract
Alongside the rapid growth in aging populations worldwide, prevention and therapy for age-related memory decline and dementia are in great demand to maintain a long, healthy life. Here we found that iso-α-acids, hop-derived bitter compounds in beer, enhance microglial phagocytosis and suppress inflammation via activation of the peroxisome proliferator-activated receptor γ. In normal mice, oral administration of iso-α-acids led to a significant increase both in CD11b and CD206 double-positive anti-inflammatory type microglia (p < 0.05) and in microglial phagocytosis in the brain. In Alzheimer's model 5xFAD mice, oral administration of iso-α-acids resulted in a 21% reduction in amyloid β in the cerebral cortex as observed by immunohistochemical analysis, a significant reduction in inflammatory cytokines such as IL-1β and chemokines including macrophage inflammatory protein-1α in the cerebral cortex (p < 0.05) and a significant improvement in a novel object recognition test (p < 0.05), as compared with control-fed 5xFAD mice. The differences in iso-α-acid-fed mice were due to the induction of microglia to an anti-inflammatory phenotype. The present study is the first to report that amyloid β deposition and inflammation are suppressed in a mouse model of Alzheimer's disease by a single component, iso-α-acids, via the regulation of microglial activation. The suppression of neuroinflammation and improvement in cognitive function suggests that iso-α-acids contained in beer may be useful for the prevention of dementia.
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Affiliation(s)
- Yasuhisa Ano
- From the Research Laboratories for Health Science & Food Technologies and
| | - Atsushi Dohata
- the Graduate School of Agricultural and Life Sciences, the University of Tokyo, Tokyo 113-8657, Japan, and
| | - Yoshimasa Taniguchi
- the Central Laboratories for Key Technologies, Kirin Company Ltd., Kanagawa 236-0004, Japan
| | - Ayaka Hoshi
- the Central Laboratories for Key Technologies, Kirin Company Ltd., Kanagawa 236-0004, Japan
| | - Kazuyuki Uchida
- the Graduate School of Agricultural and Life Sciences, the University of Tokyo, Tokyo 113-8657, Japan, and
| | - Akihiko Takashima
- the Department of Neurobiology, National Center for Geriatrics and Gerontology, Obu 474-8511, Japan
| | - Hiroyuki Nakayama
- the Graduate School of Agricultural and Life Sciences, the University of Tokyo, Tokyo 113-8657, Japan, and
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Oladokun O, Tarrega A, James S, Smart K, Hort J, Cook D. The impact of hop bitter acid and polyphenol profiles on the perceived bitterness of beer. Food Chem 2016; 205:212-20. [DOI: 10.1016/j.foodchem.2016.03.023] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 03/07/2016] [Accepted: 03/08/2016] [Indexed: 10/22/2022]
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Morimoto-Kobayashi Y, Ohara K, Ashigai H, Kanaya T, Koizumi K, Manabe F, Kaneko Y, Taniguchi Y, Katayama M, Kowatari Y, Kondo S. Matured hop extract reduces body fat in healthy overweight humans: a randomized, double-blind, placebo-controlled parallel group study. Nutr J 2016; 15:25. [PMID: 26960416 PMCID: PMC4784395 DOI: 10.1186/s12937-016-0144-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 03/02/2016] [Indexed: 12/15/2022] Open
Abstract
Background Hops are the main components of beer that provide flavor and bitterness. Iso-α-acids, the bitter components of beer, have been reported to reduce body fat in humans, but the bitterness induced by effective doses of iso-α-acids precludes their acceptance as a nutrient. The matured hop bitter acids (MHBA) of oxidized hops appear to have a more pleasant bitterness compared to the sharper bitterness of iso-α-acids. While there has been little information concerning the identity of the MHBA compounds and their physiological effects, MHBA was recently found to be primarily composed of oxides derived from α-acids, and structurally similar to iso-α-acids. Here, we investigated the effects of matured hop extract (MHE) containing MHBA on reducing abdominal body fat in healthy subjects with a body mass index (BMI) of 25 to below 30 kg/m2, classified as “obese level 1” in Japan or as “overweight” by the WHO. Trial design A randomized, double-blind, placebo-controlled parallel group study. Methods Two hundred subjects (male and female aged 20 to below 65 years with a BMI of 25 or more and less than 30 kg/m2) were randomly assigned to two groups. During a 12-week ingestion period, the subjects in each group ingested daily 350 mL of test-beverage, either containing MHE (with 35 mg MHBA), i.e. the namely active beverage, or a placebo beverage without MHE. The primary endpoint was reduction of the abdominal fat area as determined by CT scanning after continual ingestion of MHE for 12 weeks. Results Compared to the placebo group, a significant reduction was observed in the visceral fat area after 8 and 12 w, and in the total fat area after 12 w in the active group. There was also a concomitant decrease in body fat ratio in the active group compared to the placebo group. No adverse events related to the test beverages or clinically relevant abnormal changes in the circulatory, blood and urine parameters were observed in either group. Conclusions The present study suggests that continual ingestion of MHE safely reduces body fat, particularly the abdominal visceral fat of healthy overweight subjects. Trial registration UMIN-CTR UMIN000014185 Electronic supplementary material The online version of this article (doi:10.1186/s12937-016-0144-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yumie Morimoto-Kobayashi
- Research Laboratories for Health Science and Food Technologies, Kirin Company, Ltd, 1-13-5, Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
| | - Kazuaki Ohara
- Research Laboratories for Health Science and Food Technologies, Kirin Company, Ltd, 1-13-5, Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
| | - Hiroshi Ashigai
- Research Laboratories for Health Science and Food Technologies, Kirin Company, Ltd, 1-13-5, Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
| | - Tomoka Kanaya
- Research Laboratories for Health Science and Food Technologies, Kirin Company, Ltd, 1-13-5, Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
| | - Kumiko Koizumi
- Research Laboratories for Health Science and Food Technologies, Kirin Company, Ltd, 1-13-5, Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
| | - Fumitoshi Manabe
- Research Laboratories for Health Science and Food Technologies, Kirin Company, Ltd, 1-13-5, Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
| | - Yuji Kaneko
- Research Laboratories for Health Science and Food Technologies, Kirin Company, Ltd, 1-13-5, Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
| | - Yoshimasa Taniguchi
- Central Laboratories for Key Technologies, Kirin Company, Ltd, 1-13-5, Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
| | - Mikio Katayama
- Research Laboratories for Health Science and Food Technologies, Kirin Company, Ltd, 1-13-5, Fukuura, Kanazawa-ku, Yokohama, 236-0004, Japan.
| | - Yasuyuki Kowatari
- Ueno Clinic, Aiseikai Public Interest Incorporated Foundation, 2-18-6, Higashiueno, Taito-ku, Tokyo, 110-0015, Japan.
| | - Sumio Kondo
- Fukushima Healthcare Center, Kensyokai Medical Corporation, 2-12-16, Tamakawa, Fukushima-ku, Osaka, 553-0004, Japan.
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Oladokun O, Smart K, Cook D. An improved HPLC method for single-run analysis of the spectrum of hop bittering compounds usually encountered in beers. JOURNAL OF THE INSTITUTE OF BREWING 2016. [DOI: 10.1002/jib.299] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Olayide Oladokun
- Brewing Science Section, Division of Food Sciences; The University of Nottingham; Sutton Bonington campus Loughborough LE12 5RD UK
| | - Katherine Smart
- SABMiller Plc; SABMiller House, Church Street West Woking Surrey GU21 6HS UK
| | - David Cook
- Brewing Science Section, Division of Food Sciences; The University of Nottingham; Sutton Bonington campus Loughborough LE12 5RD UK
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Taniguchi Y, Yamada M, Taniguchi H, Matsukura Y, Shindo K. Chemical Characterization of Beer Aging Products Derived from Hard Resin Components in Hops (Humulus lupulus L.). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:10181-10191. [PMID: 26507444 DOI: 10.1021/acs.jafc.5b04138] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The bitter taste of beer originates from resins in hops (Humulus lupulus L.), which are classified into two subtypes (soft and hard). Whereas the nature and reactivity of soft-resin-derived compounds, such as α-, β-, and iso-α-acids, are well studied, there is only a little information on the compounds in hard resin. For this work, hard resin was prepared from stored hops and investigated for its compositional changes in an experimental model of beer aging. The hard resin contained a series of α-acid oxides. Among them, 4'-hydroxyallohumulinones were unstable under beer storage conditions, and their transformation induced primary compositional changes of the hard resin during beer aging. The chemical structures of the products, including novel polycyclic compounds scorpiohumulinols A and B and dicyclohumulinols A and B, were determined by HRMS and NMR analyses. These compounds were proposed to be produced via proton-catalyzed cyclization reactions of 4'-hydroxyallohumulinones. Furthermore, they were more stable than their precursor 4'-hydroxyallohumulinones during prolonged storage periods.
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Affiliation(s)
- Yoshimasa Taniguchi
- Central Laboratories for Key Technologies, Research & Development Division, KIRIN Company, Ltd. , 1-13-5 Fukuura Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004, Japan
| | - Makiko Yamada
- Central Laboratories for Key Technologies, Research & Development Division, KIRIN Company, Ltd. , 1-13-5 Fukuura Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004, Japan
| | - Harumi Taniguchi
- Central Laboratories for Key Technologies, Research & Development Division, KIRIN Company, Ltd. , 1-13-5 Fukuura Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004, Japan
| | - Yasuko Matsukura
- Central Laboratories for Key Technologies, Research & Development Division, KIRIN Company, Ltd. , 1-13-5 Fukuura Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004, Japan
| | - Kazutoshi Shindo
- Department of Food and Nutrition, Japan Women's University , 2-8-1 Mejirodai, Bunkyo-ku, Tokyo 112-8681, Japan
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Morimoto-Kobayashi Y, Ohara K, Takahashi C, Kitao S, Wang G, Taniguchi Y, Katayama M, Nagai K. Matured Hop Bittering Components Induce Thermogenesis in Brown Adipose Tissue via Sympathetic Nerve Activity. PLoS One 2015; 10:e0131042. [PMID: 26098641 PMCID: PMC4476742 DOI: 10.1371/journal.pone.0131042] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 05/29/2015] [Indexed: 02/03/2023] Open
Abstract
Obesity is the principal symptom of metabolic syndrome, which refers to a group of risk factors that increase the likelihood of atherosclerosis. In recent decades there has been a sharp rise in the incidence of obesity throughout the developed world. Iso-α-acids, the bitter compounds derived from hops in beer, have been shown to prevent diet-induced obesity by increasing lipid oxidation in the liver and inhibition of lipid absorption from the intestine. Whereas the sharp bitterness induced by effective dose of iso-α-acids precludes their acceptance as a nutrient, matured hop bittering components (MHB) appear to be more agreeable. Therefore, we tested MHB for an effect on ameliorating diet-induced body fat accumulation in rodents. MHB ingestion had a beneficial effect but, compared to iso-α-acids and despite containing structurally similar compounds, acted via different mechanisms to reduce body fat accumulation. MHB supplementation significantly reduced body weight gain, epididymal white adipose tissue weight, and plasma non-esterified free fatty acid levels in diet-induced obese mice. We also found that uncoupling protein 1 (UCP1) expression in brown adipose tissue (BAT) was significantly increased in MHB-fed mice at both the mRNA and protein levels. In addition, MHB administration in rats induced the β-adrenergic signaling cascade, which is related to cAMP accumulation in BAT, suggesting that MHB could modulate sympathetic nerve activity innervating BAT (BAT-SNA). Indeed, single oral administration of MHB elevated BAT-SNA in rats, and this elevation was dissipated by subdiaphragmatic vagotomy. Single oral administration of MHB maintained BAT temperature at a significantly higher level than in control rats. Taken together, these findings indicate that MHB ameliorates diet-induced body fat accumulation, at least partly, by enhancing thermogenesis in BAT via BAT-SNA activation. Our data suggests that MHB is a useful tool for developing functional foods or beverages to counteract the accumulation of body fat.
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Affiliation(s)
- Yumie Morimoto-Kobayashi
- Research Laboratories for Health Science & Food Technologies, KIRIN Company, Ltd., Yokohama, Kanagawa, Japan
- * E-mail:
| | - Kazuaki Ohara
- Research Laboratories for Health Science & Food Technologies, KIRIN Company, Ltd., Yokohama, Kanagawa, Japan
| | - Chika Takahashi
- Research Laboratories for Health Science & Food Technologies, KIRIN Company, Ltd., Yokohama, Kanagawa, Japan
| | - Sayoko Kitao
- Research Laboratories for Health Science & Food Technologies, KIRIN Company, Ltd., Yokohama, Kanagawa, Japan
| | - Guanying Wang
- Research Laboratories for Health Science & Food Technologies, KIRIN Company, Ltd., Yokohama, Kanagawa, Japan
| | - Yoshimasa Taniguchi
- Research Laboratories for Health Science & Food Technologies, KIRIN Company, Ltd., Yokohama, Kanagawa, Japan
| | - Mikio Katayama
- Research Laboratories for Health Science & Food Technologies, KIRIN Company, Ltd., Yokohama, Kanagawa, Japan
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Taniguchi Y, Matsukura Y, Taniguchi H, Koizumi H, Katayama M. Development of preparative and analytical methods of the hop bitter acid oxide fraction and chemical properties of its components. Biosci Biotechnol Biochem 2015; 79:1684-94. [PMID: 25996959 DOI: 10.1080/09168451.2015.1042832] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The bitter acids in hops (Humulus lupulus L.) and beer, such as α-, β-, and iso-α-acids, are known to affect beer quality and display various physiological effects. However, these compounds readily oxidize, and the effect of the oxides on the properties of beer or their potential health benefits are not well understood. In this study, we developed a simple preparative method for the bitter acid oxide fraction derived from hops and designated the constituents as matured hop bitter acids (MHBA). HPLC-PDA-ESI/HRMS and MS(2) revealed that MHBA are primarily composed of α-acid-derived oxides, which possess a common β-tricarbonyl moiety in their structures similar to α-, β-, and iso-α-acids. We also developed a quantitative analytical method of whole MHBA by HPLC, which showed high precision and reproducibility. Using our newly developed method, the concentration of whole MHBA in several commercial beers was evaluated. Our results will promote the study of bitter acid oxides.
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Affiliation(s)
- Yoshimasa Taniguchi
- a Central Laboratories for Key Technologies, Research & Development Division , KIRIN Company, Ltd. , Kanagawa , Japan
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59
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Taniguchi Y, Taniguchi H, Yamada M, Matsukura Y, Koizumi H, Furihata K, Shindo K. Analysis of the components of hard resin in hops (Humulus lupulus L.) and structural elucidation of their transformation products formed during the brewing process. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2014; 62:11602-11612. [PMID: 25354357 DOI: 10.1021/jf504394h] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The resins from hops (Humulus lupulus L.), which add the bitter taste to beer, are classified into two main sub-fractions, namely, soft and hard resins. α- and β-Acids in soft resin and their transformation during the wort boiling process are well-studied; however, other constituents in resins, especially hard resin, have been unidentified. In this study, we identified humulinones and hulupones as soft-resin components, in addition to 4'-hydroxyallohumulinones and tricyclooxyisohumulones A and B as hard-resin components. These compounds are all oxidation products derived from α- or β-acids. We also investigated compositional changes in the hard resin during the wort boiling process, which has a significant effect on the taste of the beer, by using model boiling experiments. The major changes were identified to be isomerization of 4'-hydroxyallohumulinones into 4'-hydroxyallo-cis-humulinones, followed by decomposition into cis-oxyhumulinic acids. These findings will be helpful in systematically evaluating and optimizing the effect of the hard resin on beer quality.
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Affiliation(s)
- Yoshimasa Taniguchi
- Central Laboratories for Key Technologies, Research and Development Division, KIRIN Company, Limited , 1-13-5, Fukuura Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004, Japan
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Steenackers B, De Cooman L, De Vos D. Chemical transformations of characteristic hop secondary metabolites in relation to beer properties and the brewing process: a review. Food Chem 2014; 172:742-56. [PMID: 25442616 DOI: 10.1016/j.foodchem.2014.09.139] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 08/20/2014] [Accepted: 09/24/2014] [Indexed: 10/24/2022]
Abstract
The annual production of hops (Humulus lupulus L.) exceeds 100,000 mt and is almost exclusively consumed by the brewing industry. The value of hops is attributed to their characteristic secondary metabolites; these metabolites are precursors which are transformed during the brewing process into important bittering, aromatising and preservative components with rather low efficiency. By selectively transforming these components off-line, both their utilisation efficiency and functionality can be significantly improved. Therefore, the chemical transformations of these secondary metabolites will be considered with special attention to recent advances in the field. The considered components are the hop alpha-acids, hop beta-acids and xanthohumol, which are components unique to hops, and alpha-humulene and beta-caryophyllene, sesquiterpenes which are highly characteristic of hops.
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Affiliation(s)
- Bart Steenackers
- Centre for Surface Science and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Leuven, Belgium
| | - Luc De Cooman
- Laboratory for Enzyme and Brewing Technology, KaHo St.-Lieven, Gebroeders Desmetstraat 1, 9000 Gent, Belgium
| | - Dirk De Vos
- Centre for Surface Science and Catalysis, KU Leuven, Kasteelpark Arenberg 23, 3001 Leuven, Belgium.
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Dušek M, Olšovská J, Krofta K, Jurková M, Mikyška A. Qualitative determination of β-acids and their transformation products in beer and hop using HR/AM-LC-MS/MS. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2014; 62:7690-7697. [PMID: 25099125 DOI: 10.1021/jf501852r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Hops represent an important source of β-acids with antimicrobial and sensory properties. Transformation products of β-acids formed during their oxidation, mainly hulupones, have been shown to have an interesting kind of bitterness. Their structures were recently elucidated using LC-TOFMS and 1D/2D NMR in solution after thermal treatment of the hop β-acids. This study demonstrates the advantages of MS detection with high resolution and accurate mass measurements. The structure of transformation products in an experimental solution of oxidized β-acids was elucidated using a newly developed method by hybrid quadrupole-Orbitrap MS. In addition to already known structures, two new ones were identified and named epoxycohulupone and epoxyhulupone. The method was verified on real samples; the profiles of these products in Sládek hops harvested in 2008 and 2012 and in corresponding beers were compared. For this purpose, a new QuEChERS assay was used for the preparation of beer samples.
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Affiliation(s)
- Martin Dušek
- Research Institute for Brewing and Malting, Prague PLC, Lı́pová 15, CZ-120 44 Prague 2, Czech Republic
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62
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Rakete S, Berger R, Böhme S, Glomb MA. Oxidation of isohumulones induces the formation of carboxylic acids by hydrolytic cleavage. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2014; 62:7541-9. [PMID: 25026227 DOI: 10.1021/jf501826h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The degradation of isohumulones in mechanistic experiments was investigated. Incubation of trans-isohumulone in the presence of l-proline led to the formation of carboxylic acids and their corresponding proline amides. In the context of isohumulones unknown amides were verified first in model incubations and then in beer for the first time by comparison with authentic reference standards via LC-MS analyses. Carboxylic acids and amides were formed preferably under oxidative conditions and increasing pH. Stable isotope experiments excluded the incorporation of molecular oxygen into carboxylic acids, strongly indicating a hydrolytic mechanism via β-dicarbonyl cleavage. The proposed mechanism includes oxidation and thereby incorporation of molecular oxygen to the isohumulone ring structure followed by hydrolytic cleavage leading to acids and amides.
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Affiliation(s)
- Stefan Rakete
- Institute of Chemistry, Food Chemistry, Martin-Luther-University Halle-Wittenberg , Kurt-Mothes-Straße 2, 06120 Halle/Saale, Germany
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63
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Taniguchi Y, Taniguchi H, Matsukura Y, Kawachi Y, Shindo K. Structural elucidation of humulone autoxidation products and analysis of their occurrence in stored hops. JOURNAL OF NATURAL PRODUCTS 2014; 77:1252-1261. [PMID: 24875004 DOI: 10.1021/np4008427] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The transformation of α-acids [in hops (Humulus lupulus L.)] to iso-α-acids (in beer) during the brewing process is well known, but the occurrence and structure of the oxidized α-acids during hop storage are not well documented. Because an understanding of these oxidized compounds is essential to optimize the effects of oxidized hops on the quality of beer, we investigated the autoxidation products of humulone (a representative congener of α-acids) using a simplified autoxidation model. Among the oxidation products, tricyclooxyisohumulones A (1) and B (2), tricycloperoxyisohumulone A (3), deisopropyltricycloisohumulone (4), and the hemiacetal 5 of tricycloperoxyhumulone A (5') were isolated, and their structures were elucidated for the first time. The occurrence of compounds 1-4 in stored hops was verified using LC/MS/MS analysis. We also monitored the levels of compounds 1-4 during hop storage using LC/MS/MS analysis.
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Affiliation(s)
- Yoshimasa Taniguchi
- Research Laboratories for Health Science & Food Technologies, Research & Development Division, KIRIN Company, Ltd. , 1-13-5, Fukuura Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004, Japan
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