The medicinal parts are the glandular hairs separated from the infructescence, the whole dried female flowers, the fresh cones (preferably with few seeds) collected before the seeds ripen, and the fresh or dried female inflorescence.
Flower and Fruit
The male flowers are yellowish-greenish, inconspicuous, and about 5 mm in diameter. The female flowers are in richly blossomed, heavily branched inflorescence. The ovary, which has 2 long, downy stigmas, is surrounded at the base by a round compressed nutlet. A yellowish fruit cone grows from the female flower. The inside of the bracts is covered with small, glossy, light yellow glandular scales, which contain hop bitter (Lupulin).
Leaves, Stem, and Root
The hop plant is a perennial. The annual shoots reach a height of 6 m (12 m when cultivated). The stems are pencil-thick, green, and do not turn woody. They are covered in 6 rows of climbing barbs. The leaves are 3 to 5 lobed, serrate, and opposite.
Lupulin has a very strong odor and an extremely bitter taste.
Indigenous to Europe, cultivated in Asia, U.S., and elsewhere.
Hop cones consist of the whole dried female inflorescence of Humulus lupulus. After the harvest, the hops are dried on racks at temperatures of 30 to 60º C.
Actions & Pharmacology
Alpha-bitter acids: including, among others, humulone, cohumulone, adhumulone
Beta-bitter acids: including, among others, lupulone, colupulone, adlupulone
Volatile oil (0.3-1.0%): very complex in makeup, chief components myrcene, humulene, beta-caryophyllene, undecane-2-on, furthermore 2-methyl-but-3-en-ol (particularly following storage, as breakdown product of the acylphloroglucinols)
Resins (oxidation products of the bitter acids)
Phenolic acid: including, among others, ferulic acid, caffeic acid and their derivatives, for example, chlorogenic acid
Tannins: oligomeric proanthocyanidines
Flavonoids: including, among others, xanthohumole
Neurosedative, antibacterial, antifungal, diuretic, antitumor, and estrogenic activities have been established. Many of the effects are thought to be due to the volatile oil (2- methyl-3-butene-2-ol), flavonoids, and/or estrogenic activity of the plant (Stephan et al, 1998; Salvador, 1994; Okamoto & Kumai, 1992; Tyler, 1988). Hops is primarily used for its mild sedative effects and for treating the gastrointestinal system. Hops in combination with valerian, balm leaf, and motherwort produced sedative effects in one human study. This effect, however, strongly depends on the quality of the extract used.
Hops is a bitter, an astringent, and a smooth-muscle relaxant with antibacterial properties. This makes it useful in the treatment of indigestion, nervous gastropathies, colitis, and irritable bowel syndrome as well as a preventive for individuals prone to ulcers.
Research has substantiated the phytoestrogenic properties of hops (Milligan et al, 1999). Animal and in vitro studies found that hops also has significant cancer-cell growth inhibition. The use of hops and phytoestrogens in general in cancer prevention is currently controversial due to an apparent concentration-dependent proliferative effect on human cell lines. Hops also caused preferential inhibition of diacylglycerol acyltransferase (DGAT) inhibition in one in vitro study. The effect of hops on blood glucose levels is unclear.
Hops has been used historically for reproductive conditions including premature ejaculation, as an anaphrodisiac in men, and for dysmenorrhea in women, but clinical evidence to support its use as a phytoestrogen is limited. Externally, an infusion or poultice of hops can be used to treat bruises, boils, and painful swellings. It is often combined with chamomile or poppy for this purpose.
Lupulone and humulone exhibit gram-positive and gram-negative antibacterial properties. Hexahydrocolupulone (HHC) (a semisynthetic derivative of colupulone and a beta acid congener of lupulone) was active against gram-positive bacteria and mycobacteria (Stephan et al, 1998). One variety and a wild type of the essential oil and solvent extract of hops were found to be active against Bacillus subtilis and Staphylococcus aureus in an in vitro study evaluating 11 hops cultivars. There was no activity against Escherichia coli. The antibacterial effect of weak acids from hops increased with decreasing pH. The essential oil was found to have antifungal effects against Trichophyton mentagrophytes var. interdigitale but no activity was seen against Candida albicans (Langezaal et al, 1992).
Theoretically, hops may inhibit tumor cell growth via the estrogenic effect of its phytoestrogen components. There is currently minimal clinical data to support this role but initial reports are suggestive (Milligan et al, 1999; Zava et al, 1998).
In an in vitro assessment of six flavonoids found in hops, xanthohumol was found to be the most effective antiproliferative agent in human breast, colon, and ovarian cancer cells. When compared to the flavonoid genistein, which is currently in clinical trials as a chemopreventive agent for breast cancer in humans, xanthohumol was found to be several-fold more potent. Hops flavonoids may inhibit cancer growth at more than one stage of the cell cycle. Inhibition of DNA synthesis may be one of the mechanisms by which some of the hop flavonoids exert their antiproliferative activity on MCF-7 cells (Miranda et al, 1999).
Hexahydrocolupulone (HHC) (a semisynthetic derivative of colupulone that is a beta-acid congener of lupulone) inhibited human tumor cell growth in vitro by a mechanism that may involve the precursor metabolism and transport, macromolecular synthesis, and/or cell-cycle or cell cycle-dependent pathways. HHC had a wide spectrum of activity against solid tumors and leukemias as well as against cells that have been resistant to chemotherapeutic agents. HHC did not damage DNA, interfere with topoisomerase, or generate free radicals (Stephan et al, 1998). Humulone, an alpha acid of hops, was found to inhibit the growth of monoblastic leukemia U937 cells in vitro while enhancing the differentiation-inducing action of vitamin D3 (Honma et al, 1998).
Dgat Inhibition Effects
Two chalcones isolated from hops extract, xanthohumol and xanthohumol B, have been shown to inhibit diacylglycerol acyltransferase (DGAT) activity preferentially. Over accumulation of triacylglycerol in certain organs and tissues has been associated with increased risk for conditions including fatty liver, obesity, and hypertriglyceridemia. DGAT has been found to be exclusively involved in the formation of triacylglycerol (Tabata et al, 1997).
Glucose Tolerance Effect
Colupulone, a beta acid of hops, was shown to produce a small but significant decrease in serum glucose in nondiabetic outbred Swiss-Webster mice 30 minutes after the administration of a test dose of glucose. In a second experiment, it caused a small but significant increase in blood glucose in C57BI/KSJ-db/db diabetic mice but had no effect on nondiabetic C57BI/KSJ-db/db mice. Further research is required to explain these effects (Mannering et al, 1994).
Estrogenic activity is thought to be due to the combined effect of many of the constituents in hops. The hormonal properties may account for its use in skin softening creams (Salvador, 1994). In vitro bioassays using a human endometrial cell line led to the identification of a potent phytoestrogen in hops, 8- prenylnaringenin, which showed equal or greater estrogenic activity than other established plant estrogens. The authors indicated that previous discrepancies over the potential estrogenic activity of hops were probably due to the variable nature of the extracts and the variety of assays used (Milligan et al, 1999). The effective use in hyperexcitable males is thought to be due to estrogenic, antiandrogenic, and antigonadotropic activity (Salvador, 1994).
Using both in vitro bioassays and saliva from human volunteers to assess in vivo bioavailability of exogenous phytoestrogens and phytoprogesterones, hops was found to be one of the six highest estradiol-binding substances out of over 150 herbs and spices. The study confirmed that an ethanol extract of hops contains a significant amount of phytoestrogens with moderate estrogenic bioactivity (Zava et al, 1998). Preliminary data suggests that phytoestrogens can have a positive impact on menopausal symptoms, cardiovascular disease, and osteoporosis (Murkies, 1998; Kurzer & Xu, 1997).
An in vitro study has shown that hop extracts antagonize the stimulatory effect of exogenous gonadotropin (PMSG) on estradiol secretion from ovarian cells via the adenylate cylcase system. (Okamoto & Kumai, 1992).
Analysis of beer extracts utilizing gas chromatography and mass spectrometry identified two phytoestrogenic substances: genistein and daidzein. These authors note that the amount of isoflavones ingested in human beer consumption would not be expected to elicit an estrogenic effect, but patients with advanced liver disease or those with insufficient metabolism of nonsteroidal estrogenic substances may result in significant accumulation resulting in an estrogenic effect (Rosenblum et al, 1992).
Hops has been shown to improve sleep in alcohol-dependent males in one study. Hops has been shown to exhibit anticonvulsant, antinociceptive, hypothermic, hypnotic, and sedative effects in mice. Hops extract at doses of 100, 250, or 500 mg/kg were administered intraperitoneally to mice 30 minutes prior to several behavioral tests (Lee et al, 1993). Neurosedative effects are due in part to 2-methyl-3-butene-2-ol in the fresh plant (Salvador, 1994). The 2- methyl-3-butene-2-ol content increases during storage (up to 0.15% in two years) suggesting that lupulone and humulone break down oxidatively generating the sedative principle (Salvador, 1994; Tyler, 1988). The sedative effect of hops is undisputed but the basis for it is not fully known (Bradley, 1992).
Water-soluble extracts of hops (Fractions 1 and 2) caused significant antigonadotropic activity including inhibition of the rise of estradiol and serum luteinizing hormone (LH) levels, which resulted in decreased release of progesterone, decreased uterine thymidine kinase (TK) activity, and decreased ovulation in Sprague-Dawley rats (Okamoto & Kumai, 1992).
A combination of valerian and hops was tested in the treatment of insomnia in a multicenter, randomized, placebo-controlled, parallel group study of 184 adults with mild insomnia. Subjects received either: (1) two tablets of standardized extracts of a valerian and hops combination for 28 days; (2) placebo for 28 days, or; (3) two tablets of diphenhydramine for 14 days followed by placebo for 14 days. The results show a modest hypnotic effect for the valerian-hops combination and diphenhydramine relative to placebo. Sleep improvements with the herbal combination were associated with improved quality of life. Both treatments appeared safe and did not produce rebound insomnia upon discontinuation during the study (Morin et al, 2005).
The sedative and estrogenic components of Hops extract (8-PN,or hopein) have potential for prevention or treatment of menopausal symptoms that the authors of this exhaustive literature review elucidate. However, they identify only two clinical trials designed to evaluate the effect of Hops on menopausal symptoms, and neither is a randomized, double blind, placebo-controlled trial that could support the internal use of Hops for benefit of its estrogenic properties. The authors conclude that a consistent dosage form would need to be developed to justify further trials and acceptance of Hops in modern medicine (Chadwick, 2006).
In a prospective, double-blind, placebo-controlled study, a Hops extract standardized to 8-prenylnaringenin (8-PN) content—possibly the first such trial of its kind to use this standardized form—was conducted to examine whether its daily intake might positively affect menopausal discomforts. Healthy women (average age 52.1 years) were enrolled in the study and given either a placebo (n=26; 19 included in final analysis) or Hop extract equivalent to daily intake of 100 ug (n=20; 19 in final analysis) or 250 ug (n=21; 17 in final analysis) of 8-PN, respectively. Participants randomized to the Hops extract standardized to 100 ug 8-PN experienced reduced menopause-related discomforts and complaints, with rapid improvement on incidence of hot flushes in particular. No dose-dependent benefit was identified for the higher 8-PN dosage (Heyerick, 2006).
A combination herbal sedative containing hops significantly improved sleep in 50 male alcohol-dependent patients in a 2-day nonparametric study. Subjects were used as their own control. Antistress tablets containing 170 mg valerian, 50 mg hops, 50 mg balm leaf, and 50 mg motherwort were administered one night and placebo containing valerian 5 mg the other night. Subjects' self-report questionnaires indicated improved sleep quality (p<0.001), reduced sleepiness the next morning (p<0.01), decrease in recall of bad dreams (p<0.001), and decrease in frequency of night waking (p<0.001). There were no differences found in the group that took the herbal supplement versus the placebo first (Widy-Tyszkiewicz & Schminda, 1997).
Topical application of humulon, a constituent in hops, suppressed the promotion of skin tumors induced by 7,12- dimethylbenz[a]anthracene (DBMA) and tetradecanoylphorbol-13- acetate (TPA) in mice. Humulon treatment resulted in a 99% reduction of the average number of tumors per mouse. Treatment with DBMA and TPA resulted in 10.3 tumors per mouse and treatment with DBMA, TPA, and Humulon resulted in 0.1 tumors per mouse. Humulon (1, 0.5 and 0.2 mg/ear) reduced arachidonic acid induced ear inflammation dose dependently. It was not as effective as indomethacin but more effective than quercetin (Yasukawa et al, 1995).
Indications & Usage
Approved by Commission E:
- Mood disturbances such as agitation, anxiety, nervousness, and restlessness
- Sleep disturbances such as insomnia
Used as a bitter and stomachic to stimulate the appetite and increase the secretion of gastric juices.
In folk medicine, Hops has been used internally for nerve pain, priapism, inflammation of the intestinal mucous membrane, and tension headaches and used externally for ulcus cruris, ulcers and skin abrasions.
Humulus lupulus is found in preparations for treating nervousness and insomnia.
Use in women with estrogen-dependent breast cancer is controversial; some authors report that it is contraindicated (Anon, 1998).
Hops are contraindicated in the presence of depression.
Not to be used during pregnancy.
Precautions & Adverse Reactions
Hops should be used with caution when given in conjunction with other central nervous system depressants, antipsychotics, or alcohol due to its sedative effect (Newall, 1996). Excessive use over a long period may cause dizziness, cognitive changes, and mild jaundice symptoms in some individuals. Hops may cause adverse effects when used during periods of menstrual disturbances, nervousness, dermatitis, hypersensitivity reactions, and respiratory allergies. The fresh plant has a sensitizing effect (hops-picker's disease), which may occur, more rarely, with the dust of the drug as well.
Acute limited intravascular hemolysis has been reported after ingestions of a tea made from hops (Ridker, 1987).
Hops was identified as the agent that provoked anaphylaxis in seven patients with an initial diagnosis of idiopathic anaphylaxis in a study of 102 patients (Stricker et al, 1986).
Malignant hyperthermia, a life threatening disorder of the skeletal muscles, was reported in five dogs after ingestion of large amounts of hops (Duncan et al, 1997).
Data available to date suggest that hops may potentiate the sedative-hypnotic effect or increase the risk of central nervous system depression experienced with barbiturates. Clinical Management: Until the clinical significance of this potential interaction has been determined, patients should be advised to avoid concomitant use of hops and barbiturates. If patients elect to combine agents despite this advice, they should be advised to avoid activities that require mental alertness, as these agents may result in excessive sedation, psychomotor retardation, and impaired reaction time.
Theoretically, patients with reduced ability to metabolize nonsteroidal estrogenic substances, such as those with liver disease, may accumulate enough to result in estrogenic activity (Rosenblum et al, 1992). Clinical Management: It is unlikely that hops will cause an additive estrogenic effect if taken with estrogens.
Mode of Administration
Comminuted drug, powdered drug or dry extract powder for infusions or decoctions or other preparations; liquid and solid preparations for internal use and externally for bath additives.
Hops is often found in combination with other sedatives.
Liquid extract — drug: 1:1 45% ethanol (V/V) (BHP83).
Tincture — drug 1:5 60% ethanol (V/V) (BHP83)
To prepare an infusion, boiling water is poured over the ground hop cones and left to steep for 10 to 15 minutes (1 teaspoonful is equal to 0.4 g drug).
For most indications, a single dose of 0.5 g is given.
To promote sleep, a single dose of 1 to 2 g drug is given; liquid extract: single dose: 0.5 to 2 mL; tincture: single dose: 1 to 2 mL.
Tea: 1 cup before bedtime for 2 to 3 days.
5 drops, 1 tablet, or 10 globules every 30 to 60 minutes (acute) or 1 to 3 times daily (chronic); parenterally: 1 to 2 mL sc acute, 3 times daily; chronic: once a day (HAB1).
Protect from light and moisture in well-sealed containers.