phytoestrogens and xanthohumol

Beer is one of the earliest human inventions and globally the most consumed alcoholic beverage in terms of volume. In addition to water, the 'German Beer Purity Law', based on the Bavarian Beer Purity Law from 1516, allows only barley, hops, yeasts and water for beer brewing. The extracts of these ingredients, especially the hops, contain an abundance of polyphenols such as kaempferol, quercetin, tyrosol, ferulic acid, xanthohumol/isoxanthohumol/8-prenylnaringenin, α-bitter acids like humulone and β-bitter acids like lupulone. 8-prenylnaringenin is the most potent phytoestrogen known to date. These compounds have been shown to possess various anti-bacterial, anti-inflammatory, anti-oxidative, anti-angiogenic, anti-melanogenic, anti-osteoporotic and anti-carcinogenic effects. Epidemiological studies on the association between beer drinking and skin disease are limited while direct evidence of beer compounds in clinical application is lacking. Potential uses of these substances in dermatology may include treatment of atopic eczema, contact dermatitis, pigmentary disorders, skin infections, skin ageing, skin cancers and photoprotections, which require an optimization of the biostability and topical delivery of these compounds. Further studies are needed to determine the bioavailability of these compounds and their possible beneficial health effects when taken by moderate beer consumption.

Topics: Animals; Anti-Bacterial Agents; Anti-Inflammatory Agents, Non-Steroidal; Antioxidants; Beer; Coumaric Acids; Cyclohexenes; Flavanones; Flavonoids; Humans; Kaempferols; Phenylethyl Alcohol; Phytoestrogens; Propiophenones; Quercetin; Skin; Skin Diseases; Terpenes; Xanthones

Xanthohumol (3'-[3,3-dimethyl allyl]-2',4',4-trihydroxy-6'-methoxychalcone) is the principal prenylated flavonoid of the female inflorescences of the hop plant ('hops'), an ingredient of beer. Human exposure to xanthohumol and related prenylflavonoids, such as 8-prenylnaringenin and isoxanthohumol, is primarily through beer consumption. Xanthohumol has been characterized a 'broad-spectrum' cancer chemopreventive agent in in vitro studies, while 8-prenylnaringenin enjoys fame as the most potent phytoestrogen known to date. These biological activities suggest that prenylflavonoids from hops have potential for application in cancer prevention programs and in prevention or treatment of (post-)menopausal 'hot flashes' and osteoporosis. Xanthohumol and 8-prenylnaringenin are metabolized into many flavonoid derivatives with modified 3,3-dimethyl allyl (prenyl) moieties. Xanthohumol is formed in lupulin glands by a specialized branch of flavonoid biosynthesis that involves prenylation and O-methylation of the polyketide intermediate chalconaringenin. Although a lupulin gland-specific chalcone synthase is known, the aromatic prenyltransferase and O-methyltransferase participating in xanthohumol have not been identified. The prenylflavonoid pathway is a possible target for breeding or biotechnological modification of hops with the aim of increasing xanthohumol levels for beer brewing and 8-prenylnaringenin levels for pharmaceutical production.

Topics: Anticarcinogenic Agents; Beer; Flavonoids; Humans; Humulus; Isoflavones; Phytoestrogens; Phytotherapy; Plant Preparations; Propiophenones

Hop-derived products may contain xanthohumol (XN), isoxanthohumol (IX), and the potent phytoestrogen 8-prenylnaringenin (8-PN). To evaluate the potential health effects of these prenylflavonoids on breast tissue, their concentration, nature of metabolites, and biodistribution were assessed and compared with 17beta-estradiol (E(2)) exposure. In this dietary intervention study, women were randomly allocated to hop (n=11; 2.04 mg XN, 1.20 mg IX, and 0.1 mg 8-PN per supplement) or control (n=10). After a run-in of >or=4 days, three supplements were taken daily for 5 days preceding an aesthetic breast reduction. Blood and breast biopsies were analyzed using HPLC-ESI-MS/MS. Upon hop administration, XN and IX concentrations ranged between 0.72 and 17.65 nmol/L and 3.30 and 31.50 nmol/L, and between 0.26 and 5.14 pmol/g and 1.16 and 83.67 pmol/g in hydrolyzed serum and breast tissue, respectively. 8-PN however, was only detected in samples of moderate and strong 8-PN producers (0.43-7.06 nmol/L and 0.78-4.83 pmol/g). Phase I metabolism appeared to be minor (approximately 10%), whereas extensive glucuronidation was observed (> 90%). Total prenylflavonoids showed a breast adipose/glandular tissue distribution of 38/62 and their derived E(2)-equivalents were negligible compared with E(2) in adipose (384.6+/-118.8 fmol/g, p=0.009) and glandular (241.6+/-93.1 fmol/g, p<0.001) tissue, respectively. Consequently, low doses of prenylflavonoids are unlikely to elicit estrogenic responses in breast tissue.

Topics: Adipose Tissue, White; Adolescent; Adult; Biotransformation; Breast; Chromatography, High Pressure Liquid; Dietary Supplements; Female; Flavanones; Flavonoids; Flowers; Humans; Humulus; Mammary Glands, Human; Middle Aged; Phytoestrogens; Propiophenones; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry; Xanthones; Young Adult

Hops, an essential beer ingredient, are a source of prenylflavonoids, including 8-prenylnaringenin (8-PN), one of the most potent phytoestrogens. Because 8-PN concentrations in beers are generally low, its health effects after moderate beer consumption were considered negligible. However, human intestinal microbiota may activate up to 4 mg/L isoxanthohumol (IX) in beer into 8-PN. Depending on interindividual differences in the intestinal transformation potential, this conversion could easily increase the 8-PN exposure 10-fold upon beer consumption. Here, we present a further investigation of the process both in vitro and in vivo. In vitro experiments with the dynamic SHIME model showed that hop prenylflavonoids pass unaltered through the stomach and small intestine and that activation of IX into 8-PN (up to 80% conversion) occurs only in the distal colon. In vitro incubations of 51 fecal samples from female volunteers with IX enabled us to separate the fecal microbiota into high (8 of 51), moderate (11 of 51) and slow (32 of 51) 8-PN producers, clearly illustrating an interindividual variability. Three women, selected from the respective groups, received a daily dose of 5.59 mg IX for 4 d. Intestinal IX activation and urinary 8-PN excretion were correlated (R(2) = 0.6417, P < 0.01). These data show that intestinal conversion of IX upon moderate beer consumption can lead to 8-PN exposure values that might fall within the range of human biological activity.

Topics: Adult; Chromatography, High Pressure Liquid; Female; Flavanones; Flavonoids; Humans; Humulus; Intestinal Mucosa; Isomerism; Phytoestrogens; Propiophenones

In recent years, the interest in the health-promoting effects of hop prenylflavonoids, especially its estrogenic effects, has grown. Unfortunately, one of the most potent phytoestrogens identified so far, 8-prenylnaringenin, is only a minor component of hops, so its isolation from hop materials for the production of estrogenically active food supplements has proved to be problematic. The aim of this study was to optimize the conditions (e.g., temperature, the length of the process and the amount of the catalyst) to produce 8-prenylnaringenin-rich material by the magnesium oxide-catalyzed thermal isomerization of desmethylxanthohumol. Under these optimized conditions, the yield of 8-prenylnaringenin was 29 mg per 100 gDW of product, corresponding to a >70% increase in its content relative to the starting material. This process may be applied in the production of functional foods or food supplements rich in 8-prenylnaringenin, which may then be utilized in therapeutic agents to help alleviate the symptoms of menopausal disorders.

Topics: Beer; Catalysis; Dietary Supplements; Flavanones; Flavonoids; Humans; Humulus; Magnesium Oxide; Phytoestrogens; Plant Extracts; Plant Preparations; Propiophenones; Temperature

Botanical dietary supplements contain multiple bioactive compounds that target numerous biological pathways. The lack of uniform standardization requirements is one reason that inconsistent clinical effects are reported frequently. The multifaceted biological interactions of active principles can be disentangled by a coupled pharmacological/phytochemical approach using specialized ("knock-out") extracts. This is demonstrated for hops, a botanical for menopausal symptom management. Employing targeted, adsorbent-free countercurrent separation, Humulus lupulus extracts were designed for pre- and postmenopausal women by containing various amounts of the phytoestrogen 8-prenylnaringenin (8-PN) and the chemopreventive constituent xanthohumol (XH). Analysis of their estrogenic (alkaline phosphatase), chemopreventive (NAD(P)H-quinone oxidoreductase 1 [NQO1]), and cytotoxic bioactivities revealed that the estrogenicity of hops is a function of 8-PN, whereas their NQO1 induction and cytotoxic properties depend on XH levels. Antagonization of the estrogenicity of 8-PN by elevated XH concentrations provided evidence for the interdependence of the biological effects. A designed postmenopausal hop extract was prepared to balance 8-PN and XH levels for both estrogenic and chemopreventive properties. An extract designed for premenopausal women contains reduced 8-PN levels and high XH concentrations to minimize estrogenic while retaining chemopreventive properties. This study demonstrates the feasibility of modulating the concentrations of bioactive compounds in botanical extracts for potentially improved efficacy and safety.

Topics: Dietary Supplements; Estrogens; Female; Flavanones; Flavonoids; Humans; Humulus; Molecular Structure; Phytoestrogens; Propiophenones; Women's Health

Humulus lupulus (hop plant) has long been used in traditional medicine as a sedative and antimicrobial agent. More recently, attention has been devoted to the phytoestrogenic activity of the plant extracts as well as to the anti-inflammatory and chemopreventive properties of the prenylated chalcones present. In this study, an Italian sample of H. lupulus cv. "Cascade" has been investigated and three new compounds [4-hydroxycolupulone (6), humudifucol (7) and cascadone (8)] have been purified and identified by means of NMR spectroscopy along with four known metabolites. Notably, humudifucol (7) is the first prenylated dimeric phlorotannin discovered in nature. Because structurally related phloroglucinols from natural sources were found previously to inhibit microsomal prostaglandin E2 synthase (mPGES)-1 and 5-lipoxygenase (5-LO), the isolated compounds were evaluated for their bioactivity against these pro-inflammatory target proteins. The prenylated chalcone xanthohumol inhibited both enzymes at low μM concentrations.

Topics: Arachidonate 5-Lipoxygenase; Chalcones; Flavonoids; Humulus; Intramolecular Oxidoreductases; Italy; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Phytoestrogens; Plant Extracts; Plants, Medicinal; Polyphenols; Prenylation; Propiophenones; Prostaglandin-E Synthases

Hops (Humulus lupulus L.) produce unique prenylflavonoids that exhibit interesting bioactivities. This study investigates the interactions between selected prenylflavonoids and breast cancer resistance protein (BCRP/ABCG2), an efflux transporter important for xenobiotic bioavailability and multidrug resistance (MDR).. ABCG2-inhibitory activity of xanthohumol (XN), isoxanthohumol (IX), 6-prenylnaringenin (6-PN), 8-prenylnaringenin (8-PN), and 6,8-diprenylnarigenin (6,8-diPN) was evaluated using mitoxantrone accumulation and vesicular transport assays. XN, IX, and 8-PN were tested for a substrate-type relationship with ABCG2 using ATPase and bidirectional transport assays. The prenylflavonoids exhibited significant ABCG2-inhibitory activities in mitoxantrone accumulation and vesicular transport assays. In the ATPase assay, XN, IX, and 8-PN inhibited baseline and sulfasalazine-stimulated ATPase activities with IC50 of 2.16-27.0 μM. IX and 8-PNalso displayed bell-shaped activation curves in Ko143-suppressed membranes, indicating a substrate-type relationship. For IX, efflux ratios of 1.25 ± 0.21 and 9.18 ± 0.56 were observed in wild type and ABCG2-overexpressing MDCKII cell monolayers, respectively. The latter was reduced to 1.25 ± 0.15 in the presence of the ABCG2-specific inhibitor Ko143, demonstrating an ABCG2-mediated efflux of IX. Additionally, evidence was shown for the involvement of ABCG2 in the efflux of 8-PN and/or its sulfate conjugate.. Prenylflavonoids are potent inhibitors of ABCG2 and therefore implicated in ABCG2-mediated food/herb-drug interactions and MDR. ABCG2-mediated efflux of prenylflavonoids may represent one mechanism that regulates prenylflavonoid bioavailability.

Topics: Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily G, Member 2; ATP-Binding Cassette Transporters; Biological Availability; Breast Neoplasms; Drug Resistance, Neoplasm; Female; Flavanones; Flavonoids; Gene Expression Regulation, Neoplastic; HEK293 Cells; Herb-Drug Interactions; Humans; Humulus; Membrane Transport Proteins; Mitoxantrone; Neoplasm Proteins; Phytoestrogens; Propiophenones; Xanthones; Xenobiotics

Hop is a well-known and already frequently used estrogenic phytotherapeutic, containing the interesting prenylflavonoids, xanthohumol (XN), isoxanthohumol (IXN), 8- and 6-prenylnaringenin (8-PN and 6-PN). Since the use of secondary standards can form a solution whenever the determination is required of certain components, not commercially available or too expensive, it was decided to develop an accessible HPLC-DAD method for the determination of these prenylflavonoids. The amounts were determined in hop extract and capsules, using quercetin and naringenin as secondary standards. After optimization of the sample preparation and HPLC conditions, the analysis was validated according to the ICH guidelines. The response function of XN, 8-PN, quercetin and naringenin showed a linear relationship. For the determination of XN, a calibration line of at least three concentrations of quercetin has to be constructed. The correction factors for XN (quercetin) and for 8-PN (naringenin) were validated and determined to be 0.583 for XN, and 1.296 for IXN, 8-PN and 6-PN. The intermediate precision was investigated and it could be concluded that the standard deviation of the method was equal considering time and concentration (RSD of 2.5-5%). By means of a recovery experiment, it was proven that the method is accurate (recoveries of 96.1-100.1%). Additionally, by analysing preparations containing hop extracts on the Belgian market, it was shown that the method is suitable for its use, namely the determination of XN, IXN, 8-PN and 6-PN in hop extract and capsules, using quercetin and naringenin as secondary standards.

Topics: Calibration; Capsules; Chemistry Techniques, Analytical; Chromatography, High Pressure Liquid; Flavanones; Flavonoids; Humulus; Phytoestrogens; Propiophenones; Quercetin; Reproducibility of Results; Xanthones

The use of chromatographic assays to assess the residual complexity of materials that are purified from natural sources by chromatographic means is, in a sense, a case of the fox watching the henhouse. Beside their static residual complexity, which is intrinsic to their metabolic origin, biologically active natural materials can also be involved in chemical reactions that lead to dynamic residual complexity. The present study examines the dynamics of the hop prenylphenol, desmethylxanthohumol (DMX), by means of quantitative (1)H-NMR (qHNMR) in a setting that mimics IN VITRO and physiological conditions. The experiments provide a comprehensive, time-resolved, and mechanistic picture of the spontaneous isomerization of DMX into congeneric flavanones, including their (1)H/(2)D isotopomers. Formation of the potent phytoestrogen, 8-prenylnaringenin (8PN), suggests that measurable estrogenic activity even of high-purity DMX is an artifact. Together with previously established qHNMR assays including purity activity relationships (PARs), dynamic qHNMR assays complement important steps of the post-isolation evaluation of natural products. Thus, qHNMR allows assessment of several unexpected effects that potentially break the assumed linkage between a single chemical entity (SCE) and biological endpoints.

Topics: Biological Products; Flavanones; Flavonoids; Humulus; Isomerism; Nuclear Magnetic Resonance, Biomolecular; Phytoestrogens; Propiophenones

Hop-derived food supplements and beers contain the prenylflavonoids xanthohumol (X), isoxanthohumol (IX) and the very potent phyto-oestrogen (plant-derived oestrogen mimic) 8-prenylnaringenin (8-PN). The weakly oestrogenic IX can be bioactivated via O-demethylation to 8-PN. Since IX usually predominates over 8-PN, human subjects may be exposed to increased doses of 8-PN. A dietary intervention trial with fifty healthy post-menopausal Caucasian women was undertaken. After a 4 d washout period, participants delivered faeces, blank urine and breath samples. Next, they started a 5 d treatment with hop-based supplements that were administered three times per d and on the last day, a 24 h urine sample was collected. A semi-quantitative FFQ was used to estimate fat, fibre, alcohol, caffeine and theobromine intakes. The recoveries of IX, 8-PN and X in the urine were low and considerable inter-individual variations were observed. A five-fold increase in the dosage of IX without change in 8-PN concentration resulted in a significant lower IX recovery and a higher 8-PN recovery. Classification of the subjects into poor (60%), moderate (25%) and strong (15%) 8-PN producers based on either urinary excretion or microbial bioactivation capacity gave comparable results. Recent antibiotic therapy seemed to affect the 8-PN production negatively. A positive trend between methane excretion and 8-PN production was observed. Strong 8-PN producers consumed less alcohol and had a higher theobromine intake. From this study we conclude that in vivo O-demethylation of IX increases the oestrogenic potency of hop-derived products.

Topics: Aged; Anti-Bacterial Agents; Diet; Dietary Supplements; Feces; Female; Flavanones; Flavonoids; Gastrointestinal Tract; Humans; Humulus; Methane; Middle Aged; Phenotype; Phytoestrogens; Postmenopause; Propiophenones; Xanthones

Hop, an essential ingredient in most beers, contains a number of prenylflavonoids, among which 8-prenylnaringenin (8-PN) would be the most potent phytoestrogen currently known. Although a number of health effects are attributed to these compounds, only a few reports are available about the bioavailability of prenylflavonoids and the transformation potency of the intestinal microbial community. To test these transformations, four fecal samples were incubated with xanthohumol, isoxanthohumol (IX), and 8-PN. Upon incubation with IX, present in strong ales up to 4 mg/L, 36% was converted into 8-PN in one fecal sample and the estrogenic properties of the sample drastically increased. In an experiment with 12 fecal cultures, this conversion was observed in one-third of the samples, indicating the importance of interindividual variability in the intestinal microbial community. Eubacterium limosum was identified to be capable of this conversion (O-demethylation) of IX into 8-PN, and after strain selection, a conversion efficiency of 90% was achieved. Finally, strain supplementation to a nonconverting fecal sample led to rapid and high 8-PN production at only 1% (v/v) addition. Up to now, the concentration of 8-PN in beer was considered too low to affect human health. However, these results show that the activity of the intestinal microbial community could more than 10-fold increase the exposure concentration. Because prenylflavonoids are present in many beers with IX being the major constituent, the results raise the question whether moderate beer consumption might contribute to increased in vivo levels of 8-PN and even influence human health.

Topics: Adult; Bacteria; Eubacterium; Feces; Fermentation; Flavanones; Flavonoids; Humans; Humulus; Intestines; Phytoestrogens; Propiophenones

A hop-based dietary supplement, marketed for natural breast enhancement, was analysed to determine the identity and biological activity of active constituents and potential biological effects in man. Extracts of the dietary supplement were analysed by LC-MS(n) and phytoestrogens identified and quantitated by reference to appropriate standards. Only hop-associated phytoestrogens were found in the dietary supplement at significant concentrations as follows (mean+/-1 S.D.); 8-prenylnaringenin 10.9+/-0.3, 6-prenylnaringenin 27.4+/-1.2, 6,8-diprenylnaringenin 0.9+/-0.1, xanthohumol 321+/-17 and isoxanthohumol 81.1+/-1.6 microg/g of dietary supplement. The oestrogenic activity of extracts in an ERalpha reporter gene assay was equivalent to 48+/-6.3 ng 17beta-oestradiol/g supplement and consistent with the 8-prenylnaringenin content. The dietary supplement extract also inhibited reductive 17beta-hydroxysteroid oxidoreductase activity, but to a greater extent than a concentration matched reference mixture of hop phytoestrogens. However, the supplement was only weakly active in mouse uterotrophic assays following administration in feed or after subcutaneous injection of extract at doses of 8-PN up to 250 times higher than that recommended for women. These preliminary findings suggest that the dietary supplement is unlikely to produce oestrogenic effects in vivo at the level of the uterus; supporting evidence is still required to demonstrate efficacy.

Topics: Animals; Breast; Dietary Supplements; Estradiol; Estrogen Receptor alpha; Estrogens, Non-Steroidal; Female; Flavanones; Flavonoids; Gas Chromatography-Mass Spectrometry; Humans; Humulus; Isoflavones; Mice; Phytoestrogens; Plant Preparations; Propiophenones; Receptors, Estrogen; Safety; Uterus