Humulus lupulus, more commonly known as hops, is a member of the mulberry family (Moraceae) (Anon 1999b). It is a perennial herbaceous liana native to Eurasia, Europe, and the United States (Anon 1999b). The female plants produce strobiles, which are cone-like reproductive structures (Anon 1999a). The common and most well-known use of H. lupulus is in the flavoring of beer. Lupulin, a resinous substance found in the strobiles, is added to beer to give the distinct bitter taste (Anon 1999b). H. lupulus has also been used for medicinal purposes. Traditionally, it has been used to aid digestion and as a mild sedative to treat insomnia (Anon. 1999a).
From about 1950 to 1970, claims had been made that hops contained high quantities of estrogens (Fenselau 1973). Fenselau, et. al. (1973), assessed the degree of estrogenic activity in hops. They tested purified essential-oil fractions, alpha and beta bitter acids, and organic solvent extracts for estrogenic activity (Fenselau 1973). They also examined several dilutions by uterine-weight assay in immature female mice (Fenselau 1973). All tests indicated that hops lacked estrogenic activity (Fenselau 1973).
Another study by Fenselau (1976), tested samples of hops to detect for the presence of tetrahydrocannabinol, THC. This psychotropic compound is the active chemical component of Cannabis sativa (marijuana). They used the selected ion mode on a combined gas chromatograph - mass spectrometer to assay for the compound in 17 samples (Fenselau 1976). No THC was found in any of the samples (Fenselau 1976).
In 1989, H. lupulus was one of twelve plants studies for the treatment of diabetes mellitus (Swanston-Flatt 1989). The studies were done in vivo in normal and streptozotocin-induced diabetic mice (Swanston-Flatt 1989). Streptozotocin is an older intravenous chemotherapeutic (Anon. 1999c). It is used in the treatment of symptomatic or progressive metastatic islet and non-islet cell carcinoma of the pancreas (USP 1995). It also has diabetogenic and hyperglycemic effects (USP 1995). It has been shown to induce diabetes and lower pancreatic insulin content in insulin promoter-mB7-l transgenic mice when given in low doses (Harlen 1995). The mice were given preparations of the herb for 28 days (Swanston-Flatt 1989). In normal diabetic mice, the hops showed no effect on their basal plasma glucose and insulin, glucose tolerance, insulin-induced hypoglycemia, and glycated hemoglobin (Swanston-Flatt 1989). In the streptozotocin diabetic mice, the hops did not significantly affect the parameters of glucose homeostasis listed above or in pancreatic insulin concentration (Swanston-Flatt 1989).
Other modern day experimentation has led to the observance of a variety of possible medicinal uses of H. lupulus, including antibacterial activity (Langezaal 1992; Simpson 1992), treatment for gastritis (Krivenko 1989; Torosyan 1974), and even cancer prevention (Anon. 1998, Buhler 1999, Yasukawa 1995).
Two studies were done on the antibacterial and antimicrobial activity of H. lupulus. Simpson (1992) performed experiments on H. lupulus to determine what factors determine its antibacterial activity. It was determined that a decrease in pH caused the greatest stimulation of antibacterial activity in the weak acids (trans-isohumulone, humulone, colupulone and trans-humulinic acid) of the hops plant (Simpson 1992). The trans-isohumulone was found to have the greatest activity (Simpson 1992). Other monovalent cations stimulated activity, but not to the extent observed by protons (Simpson 1992). Divalent cations produced mixed reactions (from little effect to reduced effect) (Simpson 1992.) The activity of the trans-isohumulone was also found to be antagonized by lipids and beta-cyclodextrin (Simpson 1992). Langezaal (1992) did a study on the antimicrobial effects of essential oils and extracts of H. lupulus. He isolated the essential oils by hydrodistillation and the extracts by soaking the strobiles in chloroform (Langezaal 1992). The compounds had anntimicrobial effects against Bacillus subtilis, Staphlococcus aureus and Trichophylon mentagrophytes var. interdigitale but none against Escherichia coli and Candida albicans (Langezaal 1992).
In 1974, Totosyan conducted a study of H. lupulus in 46 chronic hyposecretory gastritis patients. A decoction of H. lupulus was given to the patients and in 36, a positive therapeutic effect was observed (Totosyan 1974). This was due to the high secretory-motor stimulating effect of the hops (Totosyan 1974). Later, another stuliy of this type was done by Krivenko (1989). He gave an herbal complex of H. lupulus, Achillea millefolium, Urtica dioica, Cichorium, Polygonum, Matricaria chamomilla, Helichrysum arenarium, Calendula, and corn stigmas to patients suffering from chronic hyposecretory gastritis, chronic hepatocholecystitis and/or angiocholitis (Krivenko 1989). No results were reported in this document.
Recent research has examined the role of H. lupulus on cancer prevention. Songsan (1990) used spectral methods to establish the structures of isoxanthohumol, xanthohumaol, and two new chalcone derivatives 3-(isoprenyl)-2,4-dihydroxy-4, 6- dimethyoxychalcone and 2,6 dimethyoxy-4,4-dihydroxychalcone. In 1998, xanthohumol was shown to inhibit the activity of the enzyme cytochrome P450, a component in the activation of the uncontrolled division of cancer cells (Anon. 1998). This research, conducted by Buh!er (1999) looked at the effects of the flavonoids and chalcones of hops on cancer chemoprevention and cancer chemotherapy. A study by Yasukawa (1995) looked at the effects of another compound in hops: humulon, on tumor promotion. It was shown that humulon inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA) induced inflammation (Yasukawa 1995). Humulon also had a pronounced inhibition of the tumor promoting factor of TPA on the growth of mouse skin tumors that had been activated by 7, 12-dimethylbenz[a]anthracene (Yasukawa 1995).
It is evident that more research needs to be conducted before proven medicinal significance of H. lupulus can be claimed. Clearly, the emphasis of the research will be on cancer prevention. And in this era, with the discovery of compounds such as Vincristine and Vinblastine in Vinca roseus, the possibility may not be so unrealistic.
Anon. 1998. Beer Hops May Help Prevent Cancer. http://www.junkscience.com/news/thisbud.htm.
Anon. 1999a. Hops (Humulus lupulus). http://mothernature.com/ency/Herb/Hops/asp
Anon. 1999b. Hop. http://infoplease.com/ce5/CE024384.html
Anon. 1999c. Streptozotocin. http://tirgan.com/strztcn.htm
Buhler, D.R. Homepage. http://www.ehsc.orst.edu/emt/Faculty/buhlerd.htm
Fenselau, C., S. Kelly, M. Salmon, & S. Billets. 1976. The absence of tetrahydrocannabinol from hops. Food Cosmet. Toxicol. 14(1):35-39.
Fenselau, C., & P. Talalay. 1973. Is estrogenic activity present in hops? Food Cosmet. Toxicol. 11(4): 597-603.
Harlan, D.M., M.A. Barnett, R. Abe, K. Pechhold, N.B. Patterson, G.S. Gray and C.K. June. 1995. Very-low-dose streptozoticin induces diabetes in insulin promotor-mB7-l transgenic mice. Diabetes 44: 816-823.
Krivenko, V.V., G.P. Potebinia. & V.V. Loiko. 1989. Experience in treating digestive organ diseases: with medicinal plants. Vrachebnoe Delo 3: 76-78.
Langezaal, C.R., A. Chandra, & J. J. Scheffer. 1992. Antimicrobial screening of essential oils and extracts of some Humulus lupulus L. cultivars. Pharmaceutisch Weekblad. Scientific Edition 14(6):353-356.
Simpson, W.J. & A.R.W. Smith. 1992. Factors affecting antibacterial activity of hop compounds and their derivatives. Journal of Applied Bacteriology 72(4):327-334.
Songson, S., S. Watanabe. & T Saito. 1990. Chalcones from methanol extracts of Humulus lupulus. Kawasaki Med Journal. 16:117-125.
Swanston-Flatt, S.K., C. Day, P.R. Flatt, B.J. Bould & C.J. Bailey. 1989. Glycaemic effects of traditional European plant treatments for diabetes: Studies in normal and streptozotocin diabetic mice. Diabetes Research 10(2):69-73.
Torosyan, A.A. & K.S. Mardzhanyan. 1974. Common hop (Humulus lupulus) and its use in chronic hyposecretory gastritis. Biol. Zh. Arm. 27(3): 87-92.
United States Pharmacopeial Convention, Inc. 1995. USP-Dispensing Information. Vol. I. Drug Information for the Health Care Professional. Rand McNally, Mass.
Yasukawa, K., M. Takeeuchi & M. Takido. 1995. Humulon, a bitter in the hop, inhibits tumor promotion by 12-O-tetracanoylphorbol-13-acetate in two-stage carcinogenesis in mouse shin. Oncology 52 (2): 156-158.
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