Best known for their role in beer brewing, the female flowers of the hop are being increasingly used in supplements for insomnia, anxiety, and menopausal symptoms. Read more to learn about their active components, how they work, and what cell research can tell us.<\/p>\n
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Hops are the female flowers of hop (Humulus<\/em> lupulus L<\/em>.), a climbing plant belonging to the same family as hemp (Cannabaceae<\/em>). Hop most likely originated in China, Southern Caucasus and Siberia, or Mesopotamia, from where it spread to Japan, America, and Central Europe [R<\/a>, R<\/a>].<\/p>\n Due to its role in beer brewing, which accounts for 98% of its use, hop is nowadays cultivated in all warmer regions.<\/strong> The different compounds in hops add a bitter flavor to beer, prevent the growth of unwanted microorganisms during the brewing process, and stabilize foam [R<\/a>].<\/p>\n Hops have long been used in traditional medicine, especially for [R<\/a>, R<\/a>]:<\/p>\n However, many of these uses remain scientifically unproven.<\/p>\n In 2003, the European Scientific Cooperative on Phytotherapy approved the use of hops as a remedy for mood<\/a> disorders such as [R<\/a>, R<\/a>]:<\/p>\n Due to this, research has recently focused on identifying the main biologically active compounds present in hops [R<\/a>].<\/p>\n Although they are not approved by the FDA, supplements containing hops extract are marketed for improving mood disorders and menopausal symptoms. Some commercial brand names are [R<\/a>, R<\/a>]:<\/p>\n The main active components of the hop plant are found in the female flowers. Volatile oils, bitter acids, and prenylflavonoids are produced by hair-shaped glands, while the rest of flavonoid types are most abundant in seeds and specialized leaves [R<\/a>, R<\/a>].<\/p>\n The volatile oils of hops (0.3-1% of hops weight) are very rich in terpenoids, especially [R<\/a>, R<\/a>]:<\/p>\n Hops terpenoids are partly responsible for their purported anti-inflammatory, anticancer, antioxidant, and antimicrobial activities [R<\/a>].<\/p>\n Bitter acids (5-20% of hops weight) are essential to the beer brewing process and can be classified as [R<\/a>, R<\/a>]:<\/p>\n Other, less abundant bitter acids include pre- and post- lupulone and humulone. Hops \u03b1-acids undergo some chemical reactions that convert them to iso-\u03b1-acids [R<\/a>].<\/p>\n Hops also contain six different classes of flavonoids [R<\/a>]:<\/p>\n Among flavonoids, xanthohumol (1% of hops\u2019 dry weight) is the most abundant and important component. It has numerous properties and can be converted to isoxanthohumol in the stomach [R<\/a>, R<\/a>].<\/p>\n Gut bacteria<\/a> can transform isoxanthohumol to 8-prenylnaringenin, which has strong female sex hormone activity [R<\/a>, R<\/a>].<\/p>\n Although to a lower extent than in hops, active compounds can also be found in other parts of the hop plant such as male flowers (xanthohumol and bitter acids) and leaves (xanthohumol, volatile compounds, and bitter acids) [R<\/a>, R<\/a>].<\/p>\n Several studies have investigated the mechanisms of the main active components of hops extract. Importantly, these studies were done in animals and cells. The effects of these compounds may not be the same in humans.<\/p>\n Some plant substances are called phytoestrogens because they can interact with female sex hormone (estrogen<\/a>) receptors and trigger some of their responses. The main phytoestrogen found in hops is 8-prenylnaringenin<\/strong> [R<\/a>, R<\/a>].<\/p>\n Female sex hormones are recognized by two kinds of cell receptors [R<\/a>]:<\/p>\n Although most phytoestrogens preferentially bind to ER\u03b2, 8-prenylnaringenin binds to ER\u03b1. In the tissues where this receptor is found, 8-prenylnaringenin caused the following effects in animal studies [R<\/a>, R<\/a>]:<\/p>\n However, 8-prenylnaringenin can also have anti-female sex hormone effects by blocking aromatase, a key enzyme in estrogen production [R<\/a>].<\/p>\n GABA<\/a> is the main sleep-promoting neurotransmitter. Low GABA levels are also associated with disorders such as anxiety, depression<\/a>, and hyperactivity [R<\/a>].<\/p>\n In cell studies, hops extract increased GABA activity but blocked GAD<\/a>, the enzyme that produces this neurotransmitter [R<\/a>, R<\/a>].<\/p>\n In mice, both \u03b1- and \u03b2-bitter acids had antidepressant activity and increased the sedative effect of ketamine<\/a> but they differed in their effect on sleepiness induced by pentobarbital. While \u03b1-acids enhanced its effect, \u03b2-acids reduced it. Only \u03b2-acids reduced the activity of GABA [R<\/a>, R<\/a>, R<\/a>].<\/p>\n Although xanthohumol stimulates the binding of GABA to its receptors, it failed to reduce anxiety in a study in rats [R<\/a>, R<\/a>].<\/p>\n A fixed valerian-hops combination promoted sleepiness in mice and rats by binding to four different types of receptors:<\/p>\n Based on mechanistic studies, Hops extract and one of its main compounds, xanthohumol, may reduce cancer risk by preventing cancer-causing substances from damaging DNA [R<\/a>, R<\/a>, R<\/a>].<\/p>\n Xanthohumol also killed cancer cells by blocking proteins that promote cell survival, such as:<\/p>\n Other mechanisms by which xanthohumol may cause cancer cell death include:<\/p>\n Xanthohumol may also prevent the formation of new blood vessels in tumors by blocking growth pathways (NF-\u03baB and Akt) [R<\/a>].<\/p>\n Xanthohumol may reduce the production of proteins that promote resistance to radiation and chemotherapy (EGFR, STAT3, and MDR1<\/a>) [R<\/a>, R<\/a>].<\/p>\n Finally, xanthohumol reduces the ability of cancer cells to invade other tissues by:<\/p>\n These anticancer effects have been studied in cells and animals at high dosages, but often this doesn’t translate to benefits in humans, especially at normal dosages.<\/p>\nHops in Traditional Medicine<\/span><\/h3>\n
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Components<\/span><\/h3>\n
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Mechanisms of Action<\/span><\/h2>\n
1) Female Sex Hormone Mechanisms<\/span><\/h3>\n
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2) Sedative and Anti-Stress Mechanisms<\/span><\/h3>\n
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3) Potential Anticancer Mechanisms<\/span><\/h3>\n
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