Hops and crafting beer are synonymous. The flowers of the plant are rarely used for anything else above and beyond the brewing process; thus much focus of breeders, researchers, and growers has been on developing new varieties, increasing yield, and disease resistance in production primarily for the brewing industry. However, the versatility of hops runs much deeper than your average frosty mug.
Besides bitterness and aroma, hops also provide antimicrobial properties against gram-positive bacteria, helping to increase storage, stability, and sterilization of beer. Hop residues also enrich and stabilize beer foam and encourage foam lacing, which gives beer aromatic and aesthetic qualities as foam brings volatile compounds out of the beer solution to the surface for more proximate interaction with olfactory senses — all before your first sip!
Among the Suds
Hop alpha acids, beta acids, and essential oils are principally the key compounds of interest for brewers, growers, and researchers; but, within beer are trace amounts of a medicinally significant compound known as xanthohumol, the most abundant prenylated chalcone present in lupulin glands (1).
Xanthohumol was first isolated from hops in 1913 and is the only known naturally occurring methylated hop resin. Although xanthohumol is the most abundant prenylated chalcone in lupulin glands, accounting from 0.1% up to 1% of dry cone weight, it is lost in substantial amounts during the brewing process due to thermal isomerization into flavones and becoming isoxanthohumol.
Xanthohumol content in beer varies upon the beer style, recipe design, and hopping rate. More hop-forward beers such as India Pale Ales have high hop usage and therefore show a larger content of xanthohumol than pilsner or lager beers.
Secretion of xanthohumol by lupulin glands takes place in female cone bracts and in less concentration on leaves. The precursor of xanthohumol is desmethylxanthohumol and in the brewing process is converted into 8-prenylnaringenin, a highly potent phytoestrogen molecule with a wide range of potential health related benefits. In the gastrointestinal tract, isoxanthohumol is converted by microorganisms into 8-prenylnarigenin. However, a small percentage of people contain the gut biota with the ability to do the conversion. Consequently, 8-prenylnaringenin content is dependent upon xanthohumol, isoxanthohumol, and desmethylxanthomol concentrations.
Little is known of the native biological activity of xanthohumol, but like many flavonoids, it is thought that production of the compound is to protect the hop plant and the female cones from herbivory by insects, as an oxidant against stress, and roles in plant growth and development (2).
Hops and their phytoceutical properties have long been used in traditional medicine as treatment for anxiety, stress, and insomnia. Interest in xanthohumol has grown because of its many pharmacological properties, which include anti-cancer, chemoprevention, cardiovascular protection, anti-inflammation, antiobesity, antioxidation, antiviral, and as treatments for menopause and osteoporosis. These health benefits seem likely since xanthohumol is a chalconoid, which are compounds known for their positive health attributes. Today, hop powders, extracts, and teas are found in health and nutrition stores throughout the world promoting these benefits.
Lab studies have shown positive results from xanthohumol as a dietary supplement. One evaluated the effect of xanthohumol on the cognitive ability of young and old mice as a possible method to mitigate age related metabolic syndrome and memory loss (3). Young mice treated with xanthohumol showed an increase in cognitive flexibility and spatial learning, but did not significantly improve in older mice, though both sets of mice showed a reduction in fatty acids of the brain.
Recently, similar work has found xanthohumol was able to reduce body weight gain, insulin resistance, and lipids in blood stream of mice (4). One of the more important applications of xanthohumol is its use as a wide range cancer chemopreventative that inhibits the metabolic activity of procarcinogens and early stage tumor growth (5).
Unfortunately, xanthohumol exists in such extremely small amounts in beer, that in order to achieve the positive health-related benefits a person would have to consume large quantities of beer, putting an individual’s health at risk because of the negative attributes of high alcohol consumption. However, investigations of the biosynthesis pathway of xanthohumol production in hops are being studied. These investigations highlight much of the work that still needs to be accomplished such as understanding xanthohumol content of different hop varieties, influence of various production methods, postharvest storage, extraction, and recipe design on xanthohumol concentrations.
(1) Almaguer, C., Schönberger, C., Gastl, M., Arendt, E. K., & Becker, T. (2014). “Humulus lupulus — a story that begs to be told. A review.” Journal of the Institute of Brewing, 120(4), 289-314.
(2) Karabin, M., Hudcova, T., Jelinek, L., & Dostalek, P. (2015). “Biotransformations and biological activities of hop flavonoids.” Biotechnology Advances, 33(6), 1063-1090.
(3) Zamzow, D. R., Elias, V., Legette, L. L., Choi, J., Stevens, J. F., & Magnusson, K. R. (2014). “Xanthohumol improved cognitive flexibility in young mice.” Behavioural Brain Research, 275, 1-10.
(4) Miranda, C. L., Elias, V. D., Hay, J. J., Choi, J., Reed, R. L., & Stevens, J. F. (2016). “Xanthohumol improves dysfunctional glucose and lipid metabolism in diet-induced obese C57BL/6J mice.” Archives of Biochemistry and Biophysics, 599, 22-30.
(5) Stevens, J. F., & Page, J. E. (2004). “Xanthohumol and related prenylflavonoids from hops and beer: to your good health!” Phytochemistry,65(10), 1317-1330.